Forensic Photography Handbook PDF

FORENSIC PHOTOGRAPHY Handbook COLLEGE OF CRIMINAL JUSTICE EDUCATION NAME Block Forensic Photography Introduction Photography Uses of Photography History Development Light Theories of light Light & mate...

FORENSIC PHOTOGRAPHY Handbook COLLEGE OF CRIMINAL JUSTICE EDUCATION NAME Block Forensic Photography Introduction Photography Uses of Photography History Development Light Theories of light Light & material Types of Light Photographic Rays Source of light Electromagnetic spectrum Visible Spectrum Primary Colors & Secondary Colors Color mixing Attribute of colors Selective & Non-selective Mediums of light The R.A.T law Camera Introduction Essential part Types of Camera Camera & Accessories Camera & lenses Introduction Principles of Lens Action Typology of lenses Group of lenses Lens Defects Other Optical defects Sensitized Material Film structure Typology of films Classification according to use Types based on FILM SPEED (according to light sensitivity) Types based on SPECTRAL SENSITIVITY (color sensitivity). Film speed Film size Film & light Exposure ` Filter Sensitized Paper Structure of the photographic paper Types of photographic paper According to physical characteristics According to grade of printing paper Forensic Photography Forensic Photographer Importance of Crime Scene Photography Sequential Photographs of the crime Scene Three types of range photographs Marking the field of View Photographic Log Macrophotography Photomicrography Microphotography Mugshot Rogues Gallery Enlarging Photography in court of justice FORENSIC PHOTOGRAPHY INTRODUCTION Photography is an invaluable aid to modern day scientific crime detection and investigation as well as crime prevention. Perhaps it could be stated that without photography our law enforcement officer in the so-called modern day scientific crime detection would still be lagging a hundred years. The year 1839 is considered generally as the birth year of photography. Its first landmark in police history is generally confined to its application to the problem of personal identification. In those days the Bertillon system of the facial features of the criminal were measured, as well as the bone structures of the various parts of the body. These measurements were worked into a classification system and the photograph of the criminal was used to supplement the classification. Later, the Bertillon system was superseded by the fingerprint system of personal identification. Under the fingerprint system the photograph of the subject is still placed on his finger print chart, not to supplement the identification system but to have available photograph if needed for investigation purposes. This course is divided into two main topics: TECHNICAL PHOTOGRAPHY AND FORENSIC PHOTOGRAPHY. TECHNICAL: technical concepts and principles which includes characteristics of photographic rays, the use of camera, lenses, filters, structure of film and photographic papers, chemical processing and others. FORENSIC: covers investigative photography, preparation of mug file and crime scene photography. Objective: The objective of this course is to help the students become aware of the basic principles and concepts of photography. Although this course is not intended to make the students become professional photographers, it is designed to give them enough information for them to realize the vital use of photography as a significant tool in law enforcement and criminal investigation. As future law enforcers and criminal investigators, they must be knowledgeable on how to utilize effectively and efficiently photographic evidences during court proceedings. Significance: The usefulness of Forensic Photography in criminal investigation is very extensive. Small objects but of great importance in a crime committed may escape in the first phase of examination by the investigator but may be seen and recovered, only after closed examination of the photographs of the crime scene. Investigators are sometimes compelled to reconstruct or describe in court some of the details of the crime scenes they investigated several months ago. With the bulk of cases the investigator handle, perhaps he would be confused or may not exactly recall some of these details or exact location of objects. However, with the aid of photographs taken from the crime scene, investigator will not find hard time to refresh in their minds and will be able to describe or explain exactly the details in court. A good photograph of the scene is a permanent record, which is always available, especially in court presentation. In court proceedings, judges, prosecutors and defense lawyers have generally never visited the scene of the crime. Therefore, photographers should bear in mind to obtain a normal, sharp and free of distortion photograph. As a general rule, take many photograph of the crime scene and select the best. A photograph of the crime scene is a factual reproduction and accurate record of the crime scene because it captures TIME, SPACE AND EVENT. A photograph is capable of catching and preserving the: SPACE - the WHERE of the crime (Locus Criminis) TIME – the WHEN of the crime EVENT – the WHAT of the crime – what is the nature or character of the crime? PHOTOGRAPHY Photographs are also means of communication. It is language sometimes defined as the “most universal of all languages”. Photography has an advantage as language because it does not rely upon abstract symbols-words. Photography, thus, is more direct and less subject to misunderstanding. As a communication medium-has few, if any, equal. 1. Photography = Derived from the Greek word “Phos” or “Photos” which means “light” and “Grapho” means “Writing” or “Graphia” meaning “to Draw”. Sir John F. W. Herschel coined the word photography when he first wrote a letter to Henry Fox Talbot. a. = Is the art and science of reproducing image by means of light through some sensitized material with the aid of a camera, Lens and its accessories and the chemical process required in order to produced a photograph. 2. Forensic = Derived from the Latin word “Forum” which means “a market place” where people gathered for public discussion. = When used in conjunction with other science it connotes a relationship to the administration of justice. It is sometimes used interchangeably with the word legal 3. Forensic Photography is the study of notion photography, the application to police works and preparation of photographic evidence for court presentation, and this connotes legal aspects. According to (Redsicker 2001), Forensic Photography is the art or science of documenting photographically a crime scene and evidence for laboratory examination and analysis for purposes of court trial._ 4. Police Photography = Is the application of the principles of photography is relation to the police work and in the administration of justice. 5. Photograph = Is the mechanical and chemical result of Photography. Picture and photograph are not the same for a picture is a generic term is refers to all kinds of formed image while a photograph is an image that can only be a product of photography. 6. Digital Photography A method of photography in which an image is digitally encoded and stored for later reproduction. 7. Modern Photography may be defined as any means for the chemical, thermal, electrical or electronic recording of the images of scenes, or objects formed by some type of radiant energy, including gamma rays, X-rays, ultra-violet rays, visible light and infrared rays. This definition is broad enough to include not only the conventional methods of photography but almost any new process that may be developed. Technical/Legal definition USES OF PHOTOGRAPHY 1. Personal Identification = Personal Identification is considered to be the first application of photography is police work. Alphonse Bertillion was the first police who utilized photography in police work as a supplementary identification in his Anthropometry system. 2. For Communication = Photograph is considered to be one of the most universal methods of communication considering that no other language can be known universally than photograph. 3. For Record Purposes = Considered to be the utmost used of photography in police work. Different Views in photographing a. General View = taking an over-all view of the scene of the crime. It shows direction and location of the crime scene. b. Medium View = Is the taking of the photograph of the scene of the crime by dividing it into section. This view will best view the nature of the crime. c. Close-up View = Is the taking of individual photograph of the evidence at the scene of the crime. It is design to show the details of the crime. d. Extreme Close-up View = Commonly designed in laboratory photographing using some magnification such as Photomacrography and photomicrography. 4. For Preservation = Crime scene and other physical evidence requires photograph for preservation purposes. Crime scene cannot be retain as is for a long period of time but through photograph the initial condition of the scene of the crime can be preserved properly. 5. For Discovering and Proving = Photography can extend human vision in discovering and proving things such as: a. The use of Magnification Photomicrography = Taking a magnified photograph of small object through attaching a camera to the ocular of a compound microscope so as to show a minute details of the physical evidence. Photomacrogaphy = Taking a magnified (enlarged) photograph of small object by attaching an extended tube lens (macro lens) to the camera. Microphotography = is the process of reducing into a small strips of film a scenario. It is first used in filmmaking. Macrophotography = used synonymously with photomacrogaphy. Telephotography = Is the process of taking photograph of a far object with the aid of a long focus and Telephoto lens. b. Used of Artificial Light such as X-ray, Ultra-violet and Infra-red rays to show something which may not be visible with the aid of human eye alone. 6. For Court Exhibits = Almost all evidence presented in court before formally be accepted requires that they satisfy the basic requirements for admissibility which is relevancy and competency. A question of relevancy is usually proved by proving the origin of the evidence and its relation to the case and this is usually supplemented by photograph of the evidence giving reference as to where it came from.  Evidence presented in court once accepted became known as Exhibit. Either Exhibit 1,2,3 etc. for the defense or Exhibit A, B, C etc for the prosecution. 7. Crime Prevention = with the used of video camera (hidden camera) and other advanced photographic equipment crimes are being detected more easily and even to the extent of preventing them from initially occurring. 8. Police Training = Modern facilities are now being used as instructional material not only in police training as well as in other agencies. 9. Reproducing and Copying = With the use of photography any number of reproduction of the evidence can be made those giving unlimited opportunity for its examination and even allow other experts or person to examine the specimen without compromising the original. Historical Development Equipment -1700 – Camera Obscura (dark chamber) was designed by Leonardo da Vinci for accurate perspective and scale. Chemicals-1725 – 1777 – Light sensitivity of silver nitrate and silver chloride solution had been discovered and investigated. 1839 – is generally known as the birth year of photography. William Henry Fox Talbot – he had invented (calotype) at the Royal Society of London. Calotype – used paper with its surface fibers impregnated with light sensitive compounds. Joseph Niepce – He discover camera images on paper sensitized with silver chloride solution but failure. Louis Jacques Mande Daguerre - made a public demonstration in Paris “Daguerreotype in collaboration with Joseph Nicephore Niepce. The Daguerreotype formed an image directly on the silver surface of a metal plate. With Talbots “calotype the fixation was only partial while daguerre’s daguerrotypes, images were made permanent with the use of hypo. 1848- Abel Niepce de Saint-Victor introduced a process of negatives on glass using albumen (egg white) as binding medium. 1889- Gelatin emulsion printing paper was commercially introduced based films. John Frederick William Herschel coined the word “photography” 1861- James Clark Maxwell researched on color 1907 – Lumiere color process was introduced, a panchromatic film was used but with blue, green, and red filter. 1914- US Eastman Kodak Company introduce a two color subtractive process called Kodachrome. 1934- Holland. The first wire-filled bulb was introduced by Phillips. The first commercially available digital camera was the 1992 Kodak DCS-100. It used a 1.3 megapixel sensor and was priced at 13,000 dollars. The first consumer camera with a Liquid Crystal Display (LCD) on the back was the Casio QV 10 in 1995 and the first camera to use compact flash was the Kodak DC-25 in 1996. In 1999 the Nikon D1, a 2.74 mega pixel camera was the first digital SLR with a price of under 6,000 dollars. Sir John F.W. Herschel coins the word “photography”; (suggest “negative” and “positive” in the following year) and point out that image can be made permanent by dissolving away unexposed silver compounds with a solution of hyposulfite of soda (hypo or sodium thiosulfate), which he had discovered in 1819. 1839- Daguerreotype consisted of two wooden boxes perfected his photographic process. Images are made permanent by the use of hypo. The precision of details and exquisite beauty of these direct-positive images on silver plates make the Daguerreotype an immediate success. 1840- U.S. J. W. Draper is also one to produce photographic protraits using a lens with a diameter of five inches and a focus of seven inches. 1840, Australia-Hungary, J.M. Petzval designed the first lens specifically for photographic use. Its maximum aperture if f/3.6 makes it possible to take portrait exposure of less than one minute, launching the most widespread use of the Daguerreotype. The lens is produced the following year by Volglander for use in the first all-metal camera. 1843-1848- Major achievements with the paper-negative process are made by Hill Adamson and by various photographers on the continent beyond the reach of Talbot’s legal agents. 1845- F Von Marten, France, Invented the panoramic camera, wherein the lens is rotated about its optical center while a curved film is scanned by a slit. 1848- Abel Niepce de Saint Victor introduced a process of negatives on glass using albumen (egg white) as binding medium. 1850 – Louis Desirie Blanquart Evard introduced a printing paper coated with albumen to achieve a glossy surface. 1851- England. Frederick Scott Archer published a method of using collodion in place of albumen for negative on glass, “wet plate”. 1853- England. JB Dancer makes the first model of a twin lens camera for stereo photography, suggested by Sir David Brewster. 1858- France Nadar takes the first aerial photograph over Paris from a free balloon. 1861- First single lens reflex camera was patented by Thomas Sulton. 1861- Scotland. James Clerk Maxwell publishes research in color perception and the three color separation of light. He also demonstrates additive color synthesis using hand colored materials in lantern slide projectors. 1880-The first twin-lens camera was produced by the British firm, R. & J. Beck. Eastman George, an American inventor, manufactured a dry plate process in 1880, the roll film in 1884 and made it available to market in 1889, and the Kodak camera in 1888, (6 ½ X 3 ½ X 3 ½) 3 ½ to infinity, 100 exposure. 1880- England. Sir William Abney discovers the use of hydroquinone as a developing agent. 1882. England Sir William Abney produces silver chloride gelatin emulsion for printing-out paper; it takes more than ten years for this and similar materials to supplant albumen paper. 1884- US. Eastman negative paper is introduced, consisting of a light sensitive emulsion or paper which after development is made transparent enough for printing by treating with hot castor oil. 1888- US John Carbutt begin the manufacture of celluloid base sheet film. 1890- full corrected lenses were introduced. 1895- The pocket camera was designed by Frank Brownell & called it “Brownie”. 1906- a plate was placed on the market that could reproduce all colors in equivalent shades of gray. 1907- Lummiere color process was introduced, a panchromatic film was used but with blue, green, and red filter. 1914- US Eastman Kodak Company introduce a two color subtractive process called Kodachrome. 1925- The German firm of Ernst Leitz brought our to market the popular camera, LIECA. HISTORY OF DIGITAL CAMERAS 1988 - The arrival of true digital cameras. The first true digital camera that recorded the image as a computerized file was likely the Fuji DS-1P, which recorded to a 16 MB internal memory card that used a battery to keep the data. This camera was never marketed in the USA. 1992 - The first commercially available digital camera was Kodak DCS-100. It used a 1.3 megapixel sensor and was priced at 13,000 dollars. 1995 -The first consumer camera with a Liquid Crystal Display (LCD) on the back was the Casio QV 10. 1996 - The first camera to use compact flash was the Kodak DC-25. 1999 The Nikon D1, a 2.74 mega pixel camera was the first digital SLR with a price of under 6,000 dollars. This camera also used Nikon F-mount lenses which means that film based photographers could use the same lenses they already own. 2003, Canon introduced the 300D camera also known as digital rebel, a six (6) mega pixel and the first DSLR priced lesser than 1,000 dollars to consumers. Light Light is defined as an electromagnetic energy with the speed of 186,00 miles per second. Its wave travel is said to be characterized in certain extent based on velocity, wavelength and frequency of the number of vibration of the wave per second. Light wavelength is the distance measured between two (2) successive crest or through of wave and it is expressed in either Millimicron (nanometer) or Angstrom. Millimicron is the units of light wavelength which is equivalent to one-millionth part of a millimeter which the Angstrom is relatively smaller for it has an equivalent measurement of ten (10) millionth part of a millimeter. THEORIES OF LIGHT 1. The WAVE Theory (Huygens) = It is the theory that was transcribed from the motion of the water that if we observe a piece of log floating in the ocean and with the force of the air would naturally will make the log move up and down. 2. Corpuscular theory (Newton)  = this later opposed the wave theory stating that light has its effect by the motion of very small particles such as electrons. 3. Modified Wave theory (Maxwell and hertz) = Based on electromagnetics. All these theories are still considered to be of little lacking that law enforcement need not to be very focus on this but rather go along with the accepted conclusion that light is a form of energy, which is electromagnetic in form. LIGHT AND MATERIALS Materials, which allow light to pass through so that objects on the other side can be distinguished, are called transparent. Those that allow light to pass through but diffuse the flow of light so that objects on the other side cannot be distinctly seen are called translucent. Materials, which allow no light to pass through, are called opaque. When light strikes an object such light is absorbed, transmitted and or reflected practically. The amount of light transmitted or reflected depends upon the characteristics of the material, the quantity and quality of the light the angle of the source etc. THE LAW OF REFLECTION – refers to the rebounding or deflection of light. The angle of reflection depends upon the angle of the light striking the material, which is referred to as the angle of incidence. THE LAW OF REFRACTION – when the material in the path of the light is transparent a change in the direction of the light occurs. The change in the direction of light when passing from one medium to another is called the phenomenon of refraction. The change in the direction of the light is due to the change in the speed of light when passing from one medium to another. The displacement depends upon the angle of incidence, the kind of material and its thickness. Types of Light Lights can largely be classified into visible and invisible light. Visible Light = Is the type of light that produces different sensation when reach the human eye. It is the type of light, which is capable of exciting the retina of the human eye. Invisible Light = lights in which their wavelength are either too short or too long to excite the retina of the human eye i.e. X-ray, Ultrat-violet and Infra-red lights. Photographic Rays a. X-ray =Light with the wavelength between.01 to 30 millimicrons. It is produced by passing an electric current through a special type of vacuum tube. It was incidentally discovered by Conrad Welhelm Roentgen. This type of light works in the principle of shadow photography. b. Ultra-violet ray (Before the violet) = Radiation having a wavelength of 30 to 400 nanometers designed to photograph fingerprints in multi colored background, documents that are altered, decipherment of erase writing and developing invisible writing. It is commercially known as “black Light”. c. Visible Light = It refers to the type of radiation having a wavelength of 400 to 700 millimicrons designed for ordinary photographing purposes. d. Infra-red (Beyond the Red) = Considered as the photographic rays with the longest wavelength ranging from 700 to 1000 millimicrons. It is designed to take photograph of over-written documents, obliterated writing, and charred documents or for black out photography. It is sometimes referred to as heat rays). SOURCES OF LIGHT There are two sources of light, they are known as natural and artificial. Natural lights are lights which come to existence without the intervention of man and artificial lights are lights which are man made. In photography natural light is used for outdoor photography and artificial lights are utilized in indoor photography to augment the adverse lighting condition. NATURAL LIGHT The source of all daylight is the sun. The combination of color and contrast ascertains the quality of the daylight. The lighting contrast depends upon the sunlight available in the daylight, when clouds do not cover the sun. Then, the contrast is high on the contrary; if clouds cover the sun the contrast is low. In the process of photographing and object; the lighting contrast must be considered in the exposure of the film. It is suggested that the recommendations, given by the manufacturer of the film be observed religiously to produce good and presentable photographs. Color of the daylight will also affect the appearance of the objects being photographed specially in color photography. Some of the factors affecting the color of the daylight: a) atmospheric vapor b) atmospheric dust c) reflected light reached the objects and directly coming from the source. Daylight maybe classified according to its intensity. They are: a) Bright sunlight b) Hazy sunlight c) Dull sunlight. These classifications are modified by the film manufacturers like a) Open bright sunlight b) Under shade bright sunlight c) Hazy sunlight d) Cloudy bright sunlight e) Cloudy dull sunlight. To distinguish this classification of daylight according to intensity, the appearance of the shadows of the objects must be considered. In bright sunlight, the subject will produced a strong shadow, because the source of light in not covered and the objects or subjects appear glossy in open space due to direct sunlight and reflected light coming from the sky which act as a reflector. In Hazy sunlight, the sun is covered by thin cloud and the shadow appears bluish because of the decrease of light falling on the subject in open space. The shadow cast is transparent to the eye and more details are visible under this lighting condition than a bright sunlight. In dull sunlight, the sun is totally covered by thick clouds. No shadow is cast to the uniform illumination of lights all around the subjects in open space. ARTIFICIAL LIGHT Almost all artificial light sources can be used in photographing of objects, as long as the light is capable of exposing the sensitized materials (film). Some of the artificial lights are electronic flash, photoflood lamp, fluorescent lamp, and Infrared and Ultra-Violet lamp. THE ELECTROMAGNETIC SPECTRUM By using a prism made of glass or plastic, it is possible to see the colors that made up the sunlight. The colors separated in this way are called a spectrum. Another way to see the spectrum of sunlight is to look at a rainbow. The light is bend as observed, and because some of wavelengths bend more than others, the colors are separated. The violet rays are bent the most, and the red rays least. The prism experiment shows how white light is made up of a combination of wavelengths of different colored lights. To make colors it would seem that we would need paints or dyes of every possible colors and shade to get exactly what we want but in fact any color can be made by combining various proportions of the three basic colors. These are called the primary colors. The whole range of radiant energy that includes radio waves, microwaves, infrared light, visible light, ultra violet lights, x-rays and gamma rays. Visible light, which makes up only of a tiny fraction of the electromagnetic spectrum, is the only electronic radiation that humans can perceive with in their eyes. COLORS OF LIGHT FOUND IN VISIBLE SPECTRUM Visible Spectrum - a small part of the electromagnetic spectrum where the visible light is found, the portion of the electromagnetic spectrum that affect the human sense of sight. Visible light includes all those radiation having a wavelength ranging from 400 – 700 mu. COLOR Primary Colors Approximate Wavelength A. Red (longest wavelength) 700 mu B. Blue 450 mu C. Green 550 mu Complementary Colors A. Magenta (shortest wavelength) 400 B. Cyan 500 C. Yellow 590 Neutral Color A. Gray B. White  C. Black COLOR MIXING 1. Color Addition R+B+G = W R+B= M M+Y= R R+G= Y Y+C= B B+G= C Y+C= G 2. Color Subtraction W-R= C W-C=R C-G=B W-B=Y W-Y=B Y-G=R W-G=M W-M=G Y-R=G PRIMARY AND SECONDARY COLORS The three primary colors in light are red, green and blue. White light can be made by mixing red, blue and green. The process of making colors by mixing primary colors of light is called addition, because one color is added to another. Colors made by combining two primary colors are called secondary colors. They are yellow (red and green), cyan (blue and green) and magenta (blue and red). When the primary colors are mixed in different proportions any color at all can be produced. Painted objects do not produce their own light, they reflect light, when objects look red, because it is reflecting only red light to our eyes. To do this, it absorbed the other primary colors in the white light it is reflecting. It absorbed green and blue and reflects red. ATTRIBUTE OF COLORS Radiant energy within a limited frequency range has the property of stimulating the retina of the eye to create color sensation, which the brain interprets. Radiant energy, which has this property, is called light, the physical stimulus of vision. Color can be defined in qualitative terms according to certain psychological attributes. These attributes are hue, brightness and saturation. Hue is the attributes of chromatic colors, which distinguishes them from achromatic colors. Brightness is the attributes of colors, which allows the relation of colors in it to be related to given tones of gray ranging in a series from white to black. Saturation is the attribute of a chromatic color, which designates to which the color differs from a gray of the same brightness. Brightness and saturation can be understood in a practical sense from the following, take a very vivid red (single saturation) and either a small amount of white or black. The color will change to lighter or darker. In both instances, the vividness of the color is lessened (decreased saturation). The purity of the color is then affected. By adding at the same time small amount of white and black, the brightness can be held constant and only saturation is affected. When sufficient amount of white and black are added the hue becomes no longer recognized from the gray tone to which it was originally related in brightness. SELECTIVE AND NON SELECTIVE Absorption refers to the taking in of light by the material. Following the law of conservation of energy, such light taken in is not lost but merely transformed into heat. Materials in their appearance are sometimes deceiving when light strikes them. For instance, when light strikes a material and all the light is practically reflected, it will appear white. However when red light strikes the same material, it will appear red. And green light of the same material it will appear green. Such material exhibits what is called non-selective absorption. There are other materials, which behave differently as stated above, when light incident upon other such material they appear red, or blue or green but not white. With green or blue light the same material appears black because practically all lights are absorbed. A material appears red under white light because only red light is practically reflected while all other wavelengths are absorbed. Such materials which selectively reflects and absorbed others wavelength exhibits selective absorption characteristics. MEDIUMS OF LIGHT Objects that influence the intensity of light as they may reflect absorb or transmit. Mediums of light maybe classified as: TRANSPARENT OBJECTS – mediums that merely slow down the speed of light but allow to pass freely in other respects, transmit 90% or more of the incident light. TRANSLUCENT OBJECTS – mediums that allow light to pass through it in such a way that the outline of the source of light is not clearly visible, transmit 50% or less of the incident light. OPAQUE OBJECTS – A medium that divert or absorb light, but does not allow lights to pass though, they absorb most of the light while reflecting some of it. THE RAT LAW When incident light hits a medium, three things might happen, the light maybe: A. Reflected B. Absorbed C. Transmitted MECHANICAL DEVICE (CAMERA) Introduction The principle of photography are derived from science and the images on the film or paper made by the rays or light through the camera are dependent on the same general laws which produces images upon the retina through the lens which produce images upon the retina through the lens of the eye. A camera basically is nothing more than a light tight box with pinholes or lens, a shutter at one end and a holder of the sensitized material at one end. While there is various kind of camera from the simplest in construction (the box type) to the most complicated, all operate in the same principle. The exposure of the sensitized material to light is controlled by the lens and its aperture and the shutter through its speed in opening and closing the lens to light. Essential part of Camera The essentials of any camera, therefore, are light tight box, a lens, a shutter, and a holder of sensitized material. All other accessory of any camera merely makes picture taking easier, faster, and convenient for the operator and is call accessories. a. Light tight box suggests an enclosure devoid of light. An enclosure is one which would prevent light from exposing the sensitized material inside the camera. This does not necessarily mean that the box or enclosure be always light tight at all times because if it does, then no light can reach the sensitized material during exposure. Light tight box means that before and after the exposed to extraneous light which is not necessary to form the final image. b. The lens, which must be focus at the object at the time of picture taking, is one of the most important parts of any camera. The function of the lens is to focus the light coming from the subject. It operates more or less the same way as the lens of the eye. It is chiefly responsible for the sharpness of the image formed through which light passes during the exposure of the sensitized material inside the light tight box. The area of the lens may large or small during the exposure of the sensitized material depending upon the light coming form the subject to be pictured. The quantity and quality of the light coming from the subject depend upon the light source. As a rule the more light we have from the source the more light will be reflected and vice versa. Should the light be too great the area of the lens maybe reduced with the focal number adjustment. The smaller the area of the lens the greater is the numerical value of the focal number. The greater the focal number numerically the less light will pass through the lens but more distance will appear in reasonable sharpness. c. The shutter has for its function through its action called shutter speed the control of the duration of the exposure of the sensitized material to light. The higher the numerical value of the shutter speed the shorter will be the duration of the opening and closing of the lens. As an effect only a small amount of light will pass through the lens. d. The holder of sensitized material located at the opposite side of the lens has for its function to hold firmly the sensitized material in its place during exposure to prevent the formation of a multiple or blurred image of the subject. CAMERA TYPES Frequently it asked, “What is the best camera?” The answer would be the best camera is the one that takes the best pictures. Regardless of the type or kind of camera, a good operator will get results even with a cheap one. THE PINHOLE CAMERA - The simplest camera is a pinhole camera, which consists of a box with a small hole in one of its sides. To produce a sharp image, the hole must be very small and this restricts the amount of light entering the camera. Quite a long time may be necessary to let enough light through to affect the film and this causes problems because if the subject moves the picture will be blurred. It is impossible to photograph anything like a moving car or a galloping horse with a pinhole camera. CAMERA OBSCURA - Is a box used for sketching large objects? The term means dark chamber. The box contains a mirror set at 45-degree angle. Mounted in the front end of the box is a double convex lens like that in a photographic camera. Light from the object or scene is transmitted through the lens. The mirror reflects this light upward to ground glass screen on the top of the box. There the light forms an image of the object or scene that can be sketched easily. FIXED FOCUS CAMERA - The most basic of all camera, have a non-adjustable lens. Most models have a single diaphragm setting and only one or two shutter speeds. Most fixed focus cameras, including many inexpensive, pocket-sized models, use 110 or 126 size film. The negative of such film require considerable enlargement, which may produce a fuzzy image. In general, a fixed focus camera can take satisfactory photographs in ordinary daylight but not in dim light, because its lens does not admit much light. The camera may produce a blurred picture is moving or less than two meters away. Many fix-focused cameras can take flash pictures.  Disposable cameras are a kind of fixed - focus camera that combine a plastic lens, a shutter, a film in one small box. The entire camera is taken to the photo laboratory when the roll of film has been exposed. POINT AND SHOOT CAMERA - Have many automatic features that make them easy to use. Electronic devices inside the cameras automatically adjust the focus, set the light exposure and the shutter speed and advance and rewind the film. A built in electronic flash automatically supplies light when too little light reflects from the subject. The cameras are equipped with high quality lenses that produce a sharp image. Some of them have a zoom lens. Point and Shoot cameras use films that measure 35 mm. Since their introduction in 1970’s theses cameras have gained wide popularity among amateur’s photographers. SINGLE LENS REFLEX CAMERAS - Appealed to skilled amateur photographers and to professional photographers. The camera’s name refers to its viewing system. The photographer views the subject through the camera lens rather than through a separate viewing lens. A mirror between the lens and the film reflects the image onto a viewing screen. When the shutter release button is pressed to take a picture, the mirror lifts out of the way to allow the light to expose the film. Thus the photographer sees almost the exact image that is recorded on the film. SLR cameras use 35 mm film. The photographer can adjust the focus, select the shutter speed, and control the opening of the diaphragm. Many new models can also adjust the focus and control the light exposure automatically. The standard lens of the SLR camera can be replaced by special purpose lenses that change the size and depth relationship of objects in a scene. These lenses include wide-angle lens, telephoto lens, and zoom lenses. A wide-angle lens provides a wider view of a scene than a standard lens does. A telephoto lens has a narrow angle of view and makes objects appear larger and closer. A zoom lens combines many features of standard, wide angle and telephoto lenses. With other accessories, many SLR cameras can take pictures through a microscope, telescope or underwater. Reflex cameras, both the SLR and the TLR types, are equipped with mirrors that reflect in the viewfinder the scene to be photographed. The twin-lens reflex is box-shaped, with a viewfinder consisting of a horizontal ground-glass screen located at the top of the camera. Mounted vertically on the front panel of the camera are two lenses, one for taking photographs and the other for viewing. The lenses are coupled, so that focusing one automatically focuses the other. The image formed by the upper, or viewing, lens is reflected to the viewing screen by a fixed mirror mounted at a 45° angle. The photographer focuses the camera and adjusts the composition while looking at the screen. The image formed by the lower lens is focused on the film at the back of the camera. Like rangefinder cameras, TLRs are subject to parallax. In the SLR type of reflex camera, a single lens is used for both viewing the scene and taking the photograph. A hinged mirror situated between the lens and the film reflects the image formed by the lens through a five-sided prism and on to a ground-glass screen on top of the camera. At the moment the shutter is opened, a spring automatically pulls the mirror out of the path between lens and film. Because of the prism, the image recorded on the film is almost exactly that which the camera lens “sees”, without any parallax effects. Most SLRs are precision instruments equipped with focal-plane shutters. Many have automatic exposure-control features and built-in light meters. Most modern SLRs have electronically triggered shutters; apertures, too, may be electronically actuated or they may be adjusted manually. Increasingly, camera manufacturers produce SLRs with automatic focusing, an innovation originally reserved for amateur cameras. Minolta's Maxxum series, Canon's EOS series, and Nikon's advanced professional camera, the F-4, all have autofocus capability and are completely electronic. Central processing units (CPUs) control the electronic functions in these cameras. Minolta's Maxxum 7000i has software “cards” which, when inserted in a slot on the side of the camera, expand the camera's capabilities. Autofocus cameras use electronics and a CPU to sample automatically the distance between camera and subject and to determine the optimum exposure level. Most autofocus cameras bounce either an infrared light beam or ultrasonic (sonar) waves off the subject to determine distance and set the focus. Some cameras, including Canon's EOS and Nikon's SLRs, use passive autofocus systems. Instead of emitting waves or beams, these cameras automatically adjust the focus of the lens until sensors detect the area of maximum contrast in a rectangular target at the centre of the focusing screen. TWIN LENS REFLEX CAMERAS - Have a viewing lens directly above the picture - taking lens. The image in the viewfinder appears on a flat screen on top of the camera. Photographer found such a viewing screen helpful in composing a picture. Photographers do not hold the viewfinder to the eye, as they do with a fixed focus, point and shoot, and single lens reflex camera. They usually hold the camera at the chest or waist and look down into the viewfinder. The image appears reversed from left to right. In most models, nearby subjects appear lower in the picture area of the viewfinder than they appear in the photograph. Most twin lens reflex cameras use film that produces negatives measuring six by six centimeters. VIEW CAMERAS - View cameras are generally larger and heavier than medium- and small-format cameras and are most often used for studio, landscape, and architectural photography. These cameras use large-format films that produce either negatives or transparencies with far greater detail and sharpness than smaller format film. View cameras have a metal or wooden base with a geared track on which two metal standards ride, one at the front and one at the back, connected by a bellows. The front standard contains the lens and shutter; the rear holds a framed ground-glass panel, in front of which the film holder is inserted. The body configuration of the view camera, unlike that of most general-purpose cameras, is adjustable. The front and rear standards can be shifted, tilted, raised, or swung, allowing the photographer unparalleled control of perspective and focus. It is the largest and most adjustable type of camera. Most have accordion like body, with a replaceable lens in front. They have a large viewing screen instead of a viewfinder. Most models have an adjustable diaphragm and shutter speed. View cameras must be mounted on a stand for efficient operation. A photographer focuses a view camera by moving the lens end or the back end of the camera forward or backward to produce a sharp image. A view camera can provide artistic distortions of subjects more effectively than any other kind of camera. Many professional photographers use view camera for portraits and other subjects. A view camera uses sheet of film that range in size from 60 to 90 mm to 280 by 360 mm. The picture is often contact printed. A contact print is a photograph made to exactly the same size a negative. It is made by shining light through the negative, which is held in contact with light sensitive paper. INSTANT CAMERAS - Use film that provides a print without first being developed into a negative. The cameras produce a print 15 seconds to 2 minutes after the photographer takes a picture. The time varies according to the camera and to the type of film. Instant camera use film that provides pictures ranging in size from 73 by 94 mm to 508 by 610 mm. Special types of film for instant camera also provide negatives. Some instant cameras can take flash pictures and focus automatically as the photographer lines up a subject in the viewfinder. ELECTRONIC CAMERA - Create pictures that can be viewed on a television screen. The lens in most electronic cameras focuses light on light sensitive mechanism called CHARGED COUPLED DEVICE OR CCD. The CCD changes the light into electronic signals. The electronic pictures can then be stored on small magnetic discs similar to those I=used in computers. With additional equipment, electronic images can also be sent over telephone lines or printed on paper. FILM CAMERAS - Takes pictures that re-create the motion of a subject when they are viewed. Professional filmmakers generally use large cameras that take 35 or 16 mm film. Most amateur’s records on 8 mm film called super 8. Today, many amateur filmmakers use portable video cameras called CAMCORDERS. These cameras convert light reflected by the subject into electronic signals that are recorded on magnetic tape. Most film cameras and camcorders can record sound at the same as they record images. Most of them also have a zoom lens. STEREO CAMERAS - Have two identical picture taking lenses with matched shutter. When a stereo camera takes a picture, each lens photographs the same subject, but from a slightly different angle. When shown to a device called a stereoscope or seen through glasses that polarize light, the two images blend in one picture that seems to have depth. Stereo cameras are made for taking photographs or for making films. SPECIAL PURPOSE CAMERA - Have been designed for industrial, medical, military, and scientific uses they include aerial cameras used in space and underwater cameras. Folding cameras favored for their compact design and movable bellows, have been in use for many years. The camera’s lens is incorporated into the bellows, which is slid back and forth along a rail to change focus. The dark clothe covering the photographer and the box body of the camera blocks out undesirable light, which might otherwise interfere with the picture. Box cameras like this “Brownie” were the earliest cameras used by the general public. Relatively simple in design and operation, they consisted of a wooden or plastic box, a drop-blade shutter, and a holding device for  the film. Modern box cameras are similar to early models, generally featuring only one shutter speed and one opening; the very easy operation makes it a popular camera among casual photographers. The Polaroid, or instant, camera delivers a finished print directly following exposure. Although most models are somewhat larger than the standard personal camera, the advantage of this system is the convenience and speed of the results. Special film used in conjunction with the camera is designed to develop itself, and represents one of the more recent chemical revolutions in photography. Reflex cameras use mirrors to form an image of the scene to be photographed in the viewfinder. The 35-mm single-lens reflex (SLR) camera is one of the most popular cameras on the market today because of its compact size, speed, and versatility. Most models offer a combination of automatic and manual options.. CAMERA WITH LENSES A lens can be used to focus the light onto the film to produce a bright, clear image. The hole behind the lens is called the aperture and on many cameras the size of the hole, or aperture can be altered. The length of time that light is allowed to enter the camera is called the exposure and is controlled by the shutter. In its normal position the shutter is closed and prevents light entering the camera. When the button is pressed, the shutter flies open for a pre - determined length of time, depending on the light conditions in which the photograph is being taken. This can be as long as one second or as short as 1/1000 second or even shorter. On a dull day you need a longer exposure than on a sunny day. Both the diaphragm and the shutter need to be adjusted according to the amount of light that is available for taking a photograph. At midday in summer there will probably be plenty of light. On a winter afternoon there may not. In a living room at night, the light maybe quite good for the eye, but not enough for the camera. A camera is essentially a sealed with an opening at one end to admit light and a device at the other end for holding photographic film or other light sensitive material. THE CAMERA AND ACCESSORIES LENS – The lens of a camera consist of one or more glass or plastic disk with flat, concave, or convex surfaces, each disk is called element. The purpose of the lens is to focus light on the film. The focal length of the lens is the distance between the optical center and the film. For any given film size, the shorter the focal length is, the greater the field of view – that is, the greater the area covered in the picture. Focal length also affects depth of field – the amount of the foreground and background that will be in sharp focus in the picture. The shorter the focal the greater is the depth of field. Lenses of various focal lengths can be used interchangeably on some cameras, allowing the photographer to vary the field of view without taking the camera to a different position. A zoom lens has an adjustable focal length and stays focused on one object as its focal length is change. The light power of the lens is determined by the ratio of its focal length to its effective diameter (the effective diameter is equal to the diameter of the aperture - the circular opening that controls the amount of light that passes through the lens). The ratio expressed with the symbol f/, is called the f- number. The larger the aperture in relation to the focal length, the smaller is the f- number. SHUTTER – The shutters on most cameras can be adjusted to different shutter speeds. The shutter speed means the length of time the shutter is open. This might be several seconds ( or even hours if you are photographing a night sky ) or one thousandth of a second or even less with special cameras. Most cameras have a shutter speed dial showing speeds from one second to, for example, one thousand of a second. The dial is set to the speed the photographer wants. Of course, the faster the shutter speeds the shorter the time the shutter is open and the smaller the amount of light let in. Shutter speed are arrange so that each setting will let in half the amount of light let it half the amount let in by the one below it and twice the amount of the one above it. There is usually also a time exposure setting so that the shutter can be left open for minutes or even hours in certain conditions.  The shutter is a device that prevents light from reaching the film until the photographer is ready to take a picture. When a lever or button is released or button is pushed, the shutter is released, and a spring or magnet snaps its aside, exposing the film to light for a certain light of time. The length of time is adjustable on all but the simplest camera,, it ranges from one second to 1/1000 of a second or less. Most adjustable cameras are capable of making time exposure – exposure of more than one second. Typically, time exposure is made by using a special shutter setting marked “T “(FOR TIME) or “B’ (FOR BULB) referring to a shutter release device used with early cameras. An adjustable speed shutter is one of two devices a camera has to permit the photographer to regulate the amount of light reaching the film ( the diaphragm is the other ) At a given aperture setting, a small shutter speed will let more light reach the film than a fast shutter speed. However, the lower the shutter speed, the greater is the chance that the image on the film will be blurred by the movement of the subject or camera. Some cameras have electronic shutter control. After the shutter is released the control uses a light sensing device called a photocell to determine when enough light has been received for a proper exposure and it then it closes the shutter automatically. The shutter is located behind the lens, between the elements of the lens (between the lens shutter) or immediately in front of the films (focal plane shutter). The shutter is a sliding door that allows light to pass through the aperture (opening) onto the film. Different settings on a small dial on the top of the camera determine how long the shutter will remain open. The aperture selector is on the body of the lens. The numbers that indicate the size of the aperture are called f-numbers or f-stops. The f-stop is equal to the ratio of the focal length of the lens to the diameter of the opening. The shutter speed and f-stop determine the exposure—that is, the overall amount of light that will reach the film. However, even when the amount of light is constant, the effect may be different. Photographers experiment with different combinations to achieve various effects. The shutter, a spring-activated mechanical device, keeps light from entering the camera except during the interval of exposure. Most modern cameras have focal-plane or leaf shutters. Some older amateur cameras use a drop-blade shutter, consisting of a hinged piece that, when released, pulls across the diaphragm opening and exposes the film for about 1/30th of a second. In the leaf shutter, at the moment of exposure, a cluster of meshed blades springs apart to uncover the full lens aperture and then springs shut. The focal-plane shutter consists of a black shade with a variable-size slit across its width. When released, the shade moves quickly across the film, exposing it progressively as the slit moves. DIAPHRAGM – The diaphragm changes the size of the aperture of the lens. Like a shutter with valuable speed, a diaphragm regulates the amount of light reaching the film. The diaphragm also affects depth of field – the smaller the aperture the greater the depth of field. The diaphragm controls the size of the aperture in the same way as the iris of the eye, if you look at a cat’s eye when it comes in out of the darkness you will that the irises have contracted to make the pupils bigger. After a few moments in a bright light the irises expand and cause the pupils to become much smaller. The aperture of the camera must also be larger in dim light and smaller in bright light. The diaphragm is usually a ring of overlapping metal leaves, which can be adjusted. The control settings for the diaphragm are referred to as f – stops and going from one f – stop to the next reduces the amount of light by one half. The common setting are f /2.8, f/4, f/5.6, f/8, f/11, f/16 and f/22. The diaphragm usually consists of a series of movable blades attached to a supporting ring. Its various positions are called stops, or f – stops. The diaphragm is controlled by a hand operated ring or lever, or by automatic electromechanical device. Simple cameras do not have diaphragm, so the aperture can not be changed. Most cameras with diaphragms have a series of standard f- stop numbers marked on the lens mount, in some cameras, theses numbers are also visible in the viewfinder. At each succeeding stop, the lens admits half as much light as at the previous one. As the shutter speed is increased, the aperture must be larger, if the same amount of light is to reach the film. The amount of light reaching the film is the same at f/8 and 1/500 of a second as at f/11 and 1/250 ( the setting of f/8 provides twice as much light f/11, but the shutter speed of 1/500 provides half as much light as 1/250). In taking pictures, a photographer will often select a particular shutter speed and then adjust the f – stop for getting the proper exposure or the photographer will select a particular f-stop and then adjust the shutter speed. The diaphragm, a circular aperture behind the lens, operates in conjunction with the shutter to admit light into the light-proof chamber. This opening may be fixed, as in many amateur cameras, or it may be adjustable. Adjustable diaphragms are composed of overlapping strips of metal or plastic that, when spread apart, form an opening of the same diameter as the lens; when meshed together, they form a small opening behind the centre of the lens. The aperture openings correspond to numerical settings, called f-stops, on the camera or the lens. The function of the Diaphragm (F/Number) 1. By expanding or contracting the diaphragm or increasing or decreasing the F/ number numerically it is possible to regulate the amount of light passing through the lens reaching the sensitized material. 2. By expanding or increasing or decreasing the f/number numerically it is possible to control the depth of field. 3. By expanding or contracting the diaphragm, it is possible to control the degree of sharpness due to lens defects. VIEWING AND FOCUSING DEVICES – The viewfinder shows the photographer the scene being photographed. It maybe a viewing screen, a miniature lens system, or a sample wire frames. Most modern cameras also have some sort of viewing system or viewfinder to enable the photographer to see, through the lens of the camera, the scene being photographed. Single-lens reflex cameras (SLRs) all incorporate this design feature, and almost all general-use cameras have some form of focusing system as well as a film-advance mechanism.  LENS APERTURE – Adjustable cameras are equipped with an iris diaphragm, a device located in or near the lens and consisting of thin overlapping leaves that fold together to create a hole of continuously variable size. In this way the aperture or lens opening, can be adjusted to admit more or less light as required. The diaphragm is usually marked with a series of settings called STOPS, which are designated by F- NUMBERS, such as f/5.6 or f/5.8. The f/ number expresses the ratio of focal length to aperture. The larger the number, the smaller the aperture. To “stop down” or “close one stop” is to set the diaphragm control at the next smaller marked stop, for instance from f/4 to f/6, or from f/6 to f/11. This reduces the amount of light admitted by one half. To open up one stop, means to set the diaphragm control at the next wider aperture. DEPTH OF FIELD - The lens aperture not only controls the amount of light entering the camera, it also affects another fundamental aspect of the photograph – depth of field. Depth of field is the range in front of and behind a sharply focused subject in which details also look sharp in the final photographic image. It depends on lens aperture, the focused distance, and the focal length of the lens. A small lens aperture, great camera to subject distance, and focal length result in greater depth of field. SHUTTER SPEED AND MOTION – Shutter speed determines how effectively a moving object can be stopped, that is, how sharply it can be reproduced without blurring, or streaking in the final image. With a fast shutter speed, the shutter is opened only briefly and the moving object has little time to change its position before exposure is completed. With a slow shutter speed, on the other hand, the shutter remains open for a relatively long time. Thus, the faster the shutter speed, the sharper the moving object will appear on the final image, and the slower the shutter speed, the more blurred object will appear. The camera shutter must stop the subjects’ apparent speed or the speed at which its image move across the film, regardless of the subjects’ actual motion through space. Factors such as distance, direction of motion, and focal length of the lens must all be taken into consideration. Generally, the closer the moving subject is to the camera, the greater it’s apparent, motion will be. Thus, if they wish to get sharp image, most photographers avoid extreme close – ups of moving subjects. FILM TRANSPORT MECHANISM – Moves new, unexposed film into position for the next picture. FILM ADVANCER – Necessary so that the exposed film can be transferred to the take up spool while the unexposed film remain on the opposite side of the lens for another exposure. FILM ADVANCE LEVER FILM REWIND CRANK FILM REWIND KNOB FILM TAKE-UP SPOOL SHUTTER SPEED DIAL – Controls the opening and closing of the shutter, regulates the quantity of light that reaches and affects the sensitized material, a dial which sets the length of time in which the light is allowed to enter the camera. SHUTTER RELEASE BUTTON – The “click” of the camera that releases the shutter FOCUSING MECHANISM – The mechanism that estimates the appropriate objects distance from the camera to form a sharp or clear image on the photograph. FOCUSING RING – The outer ring of the lens which is rotated or adjusted to obtain a clear and sharp photograph and it enables the photographer to adjust focal range. F-STOP RING F-NUMBERS ASA DIAL/SHUTTER SPEED DIAL FLASH UNIT FLASH TERMINAL FLASH ACCESSORY SHOE  TIMER/SELF-TIMER CABLE RELEASE TRIPOD CAMERA LENSES Introduction A camera lens is a transparent material made of glass or plastic, which has two opposite symmetrical and spherical surfaces. A lens is also a piece of transparent material that has at least one curved surface. The lenses refract (bend) light rays and in doing so can form images of an object. The image maybe larger, smaller or the same as the object itself. The higher the numerical value of the shutter speed, the shorter will be the duration of the opening and closing of the lens. As an effect only small amount of light will pass through the lens. Artificial lenses are made of various transparent materials such as glass, plastics or crystals. Quartz crystals are used to refract ultra violet light, which a very short wavelength. Interchangeable lenses allow a photographer to capture a variety of pictures that would otherwise be difficult or impossible to obtain with a single camera. For instance, a zoom lens may be used to photograph individual drops of dew on a spider’s web. A telephoto lens might be used to shoot a close-up view of a dangerous or easily frightened wild animal. Other options provided by special lenses include wide-angle lenses such as the fisheye lens, which curves outward to show a view of 180 degrees or more. The lens is as important a part of a camera as the body. Lenses are referred to in generic terms as wide-angle, normal, and telephoto. The three terms refer to the focal length of the lens, which is customarily measured in millimetres. Focal length is defined as the distance from the centre of the lens to the image it forms when the lens is set at infinity. In practice, focal length affects the field of view, magnification, and depth of field of a lens. A fourth generic lens type, the zoom lens, is designed to have a variable focal length, which can be adjusted continuously between two fixed limits. Zoom lenses are especially useful in conjunction with single-lens reflex cameras, for which they allow continuous control of image scale. Principles of Lens Action The ability of a lens to bring light to a focus or make it diverge derives from the fact that the velocity of light changes as the light passes through different materials. Thus when a ray of light leaves the atmosphere and enters a lens, it slows down. According to the angle at which it strikes the lens surface, it is refracted – that is, it changes direction. The ratio of velocity of light in air to its velocity in the lens material is called the index of refraction of the material. A lens refracts light rays in such a way that on of three things will occur: 1. The rays will come together at a point. 2. The rays will produce an image. 3. The rays will move in parallel lines or in diverging lines. A LENS can be used to focus the light onto the film to produce a bright, clear and sharp image. The hole behind the lens is called the aperture and on many cameras the size of the hole or aperture can be altered. The length of time that the light is allowed to enter the camera is called the exposure and is controlled by the shutter. In its normal position the shutter is closed and prevents the light entering the camera. Both the diaphragm and the shutter need to be adjusted according to the amount of light that is available for taking a photograph. All photographic lenses do the same basic job. Collect light rays from a scene in front of the camera and project them as images unto the film at the back. However, the choice of lenses also plays a very important role in the creative aspects of photography. CAMERA LENSES CAN BE USED TO CONTROL THE 1. Amount of light that reaches the film. 2. Magnification of the image. 3. Lastly, area of the image to be recorded on the film. TYPOLOGY OF LENSES There are two types of lenses, the converging and diverging lens. As to converging lenses we have the double convex, Plano convex and the concavo-convex. Under diverging lenses we have double concave, Plano concave and the concavo concave. 1. CONVEX LENS – DIVERGING LENS A convex lens causes light rays to converge, or come together, and is called a positive lens. A positive lens focuses light form a distant source into visible image that appears on then opposite side of the lens to the object. A convex lens is thicker in the middle than at the edges. When parallel rays of light pass through this type of lens, they are bent inward and meet at a point called the focus. The distance from the center of the lens to the focus is known as the focal length. The size, position, and type of image produced by a converging lens vary according to the distance of the object from the lens. If an object is more than one focal length from the lens, an inverted real image of it is formed on the opposite side of the lens. Light rays from the object pass through a real image and can be focused on a screen. When an object is located a distance of two focal lengths on a converging lens, the image is the same size as the object and is located on the opposite side of the lens. A smaller image of the object can be obtained by moving the objects by more than two focal lengths from the lens. Placing the object between one and two focal lengths from the lens can produce a larger image. If the object is less than one focal length from the lens, no real image can be formed. Instead a magnified virtual image is formed behind the object and is right side up. Light rays from the object do not pass through a virtual image, and such an image cannot be focused on the screen. A convex lens has a thick centre and thinner edges. Light passing through a convex lens is bent inward, or made to converge. This causes an image of the object to form on a screen on the opposite side of the lens. The image is in focus if the screen is placed at a particular distance from the lens that depends upon the distance of the object and the focal point of the lens. This diagram shows how rays of light starting from a point, O, on the object, strike the lens and are then brought to focus at another point, I. The same applies to every point on the object, as is shown by the pair of points P and J; thus an image, exactly similar to the object is built up. 1. SIMPLE CONVEX – convexo – convex 2. SPECIAL CONVEX – special positive lens a. – Plano – convex b. – convexo – concave  2. CONCAVE LENS – DIVERGING LENS Concave lens or negative lens spreads the light depends on the amount of curved on the faces of the lens. The distance between the lens and the image it produces is called the FOCAL LENGTH. The shorter the focal length, the smaller the image. The greater the curvature of the faces of the lens, the shorter its focal length will be. Lens that posses at least one surface that curves inward. It is a diverging lens, spreading out those light rays that have been refracted to it. Concave lens is thicker at the edges than they are at the center. Light rays passing through a diverging lens are bent outward. Diverging lens form only virtual image. SIMPLE CONCAVE – concavo – concave - Biconcave lens (with both surfaces curved inward) SPECIAL CONCAVE – special negative lens a. Plano - concave – lens with one flat surface and one concave. b. Concavo – convex A concave lens is curved inward; it is shaped like two dishes placed back-to-back. Light passing through a concave lens bends outward, or diverges. Unlike convex lenses, which produce real images, concave lenses produce only virtual images. A virtual image is one from which light rays only appear to come. This one appears as a smaller image just in front of the actual object (in this case a shamrock). Concave lenses are generally prescribed for myopic, or short- sighted, people. Concave lenses help the eyes to produce a sharp image on the retina instead of in front of it. © Microsoft Corporation. All Rights Reserved. 3. COMPOUND LENSES Simple lenses generally produce aberrated (imperfect) images. This imperfection in image formation can be reduced using compound lenses. GROUP OF LENSES ACCORDING TO THE ANGLE OF VIEW 1. Normal Lens – A lens with a focal length equal to the diagonal measure the image area. The image area of 35 mm camera is 24x36 mm, thus a normal lens for any 35 mm SLR is 50 mm international standards, 50 mm lens may have an actual focal length of 48 – 52 mm, and the normal lens has a picture angle of 5 degrees that correspond to the viewing angle of the human eye. CHARACTERISTICS:  Optimum area coverage than any lens type.  Minimum distortion and fewer common lens defects.  Angle of view equal to 75 degrees but not less than 45 degrees. 2. Wide Angle Lens – The wide-angle lens has a shorter focal length than the normal lens. As a result, it covers a picture angle of 60 – 90 degrees. It enables photographing a widely extended scene from a close proximity or within  a confined area. The range for wide angles for 35 mm SLR cameras includes 8mm, 24mm, 28 mm, and 35 mm. The 28 mm and 35 mm are the most important for general wide angle for police work. CHARACTERISTICS:  Reduced scale but increases area coverage compared with any lens at the same distance.  Increased deep perception at a given scale.  Increased distortion toward the edges of the negative material.  Reducing illumination from the center toward the edges of the negative material.  Angle of view exceeds 75 degrees. 3. Telephoto Lens – as telephoto lens, or long focus lens has a longer focal length and provides a close up image of a distant object. In contrast to the wide-angle lens, the telephoto lens covers a small field of view and a shallower depth of field. Because of shallow depth of field, there will be lack of sharpness of the subject focus areas in the photograph to be produced. Another characteristics of the telephoto lens is production of flat composition, far objects appear enlarged while near objects do not appear proportionally large. CHARACTERISTICS:  Increase scale but reduced area coverage compared to any lens type.  Decreased depth perception.  Image quality usually deteriorates which is apparent when subject is in great motion.  Angle of view less than 45 degrees. Lenses beyond 58 mm are included in the group of telephoto lenses. For identification shots in police works, lenses of 85 to 135 mm focal length are frequently used. Long tele lenses are those beyond 200 mm. 4. Super wide Angle Lenses – In this category are fish eye lenses with a 180 degrees angle of view. Focal lengths run from an amazing 6 mm to about 18mm. F stop ranges begin at F 1.8 but average f 3.5 and f 4. 5. Macro Lenses – The word macro is derived from the Greek word and means, “ to enlarge “. In photographic terms, a macro lens is designed with extended focusing capabilities to shoot a few inches from a subject. A lens used for close up photography particularly in taking pictures in minute objects. Using a macro lens, the subject being photographed will appear bigger than its actual size. This group of lens is most helpful in fingerprint work, in recording evidences such as pollen grains, hair, fiber and the like. Two Main Types of MACRO LENS: - One is meant to be used on a held tripod mounted camera and ranges from 40 mm to about 90 mm with the average about 25 mm. - The other type is either a wide angle or a lens with a focal length with 100 mm or more and is designed with a close up bellows attachment to the camera. The longer lenses give a larger image and are most suitable for static subjects and painstaking photography. 6. Zoom Lenses – The macro zoom is relatively new in both long and short-range classes. By turning a ring on the lens barrel, you are able to focus as close as three four inches and still use zoom capability. Such lens gives you close – ups as well as variable focal lengths. and the macro zoom is taking this field. A final zoom category is the variable- focal length lens that operates in the same manner as the zoom. 7. Special Purpose Lenses – Two special- purpose lenses in particular should be familiar to you. The first is adjustable through movement of the front portion up and down for perspective control (PC). Architectural photographers benefit using a PC lens that offers some control of perspective similar to the using the tilting front and back of a view camera.  The other lens, a guide-number (GN) lens, includes a diaphragm mechanism that changes aperture as the lens is focused to synchronize exposure and distance with specific flash attachment on the camera. A GN lens can be handy, but the use of automatic electronic flash unit would make the GN lens unnecessary. Incidentally, a number of compact 35 mm range finder cameras with fixed (non interchangeable) lenses are guide- number equipped. As a flash unit slips into the accessory shoe on top of the camera a small pin is activated that synchronizes change of aperture with focusing. In this way distant subjects are photographed through wider f tops than close ones, giving the effect of exposure automation. 8. Add – On Teleconverter Lenses – Add-on lenses. Principal among add- on lenses is the fishnet lens that is screwed into the front of a normal 35 mm camera lens, offering a super wide effect for less cost than a separate fisheye lens. LENS DEFECTS No lens is perfect in every respect. Usually a lens maker tries to find the best compromise among such qualities as sharpness of definition, speed of light transmission, simplicity of construction and others. Special purpose lenses however are computed for a single purpose only and in order to achieve the maximum of usefulness in one special field, other qualities are sacrificed. Except, the very finest lenses, traces of the following common lens defects will be found in all, such as chromatic aberration, spherical aberration, curvilinear, distortion, curvature of field, astigmatism and others. No camera lens will produce defects so exaggerated as the ones which will be demonstrated. However, even considerably less pronounced fault manifestation maybe enough to produce fuzziness, which usually becomes more severe toward the edges of a picture. ABERRATION in optics, is the failure of light rays to focus properly after they pass through a lens or reflect from a mirror. Proper focus occurs when the light rays cross one another at a single point. ABERRATION occurs because of minute variations in lenses and mirrors, and because different parts of the light spectrum are reflected or refracted by varying amounts. ABERRATION also defined as an optical imperfection responsible for image distortion. It can be avoided by combining several lenses and by elimination of marginal rays refracted through the outer edges of the lens. Lenses or mirrors that are sections of spheres produce spherical aberrations. If a beam of parallel rays reflects from a concave mirror, the rays that reflects from the center of the mirror cross one another at a single point. The rays that reflects far from the center cross at points closer to the mirror surface. The imaginary line connecting these points of focus is called a CAUSTIC. A CAUSTIC appears as a bright line if it shines on a surface. For example, when sunlight shines through the open top of a glass of milk and onto the curve interior acts as a mirror. Consequently, the light reflects onto the milk in a caustic curve. Without aberration, a bright spot would appear on the milk. Convex lenses also produce spherical aberration. The light rays that pass through the middle of the lens focus farther from the lens than do the rays that pass through the lens of the edges. If the lens is in a camera, the image on this is blurry. To sharpen the image, a camera has a small opening called a stop. The stop allows only the rays passing through the center of the lens to reach the film. Thus, the rays focus at one spot on the film, and the picture is clear. There are six ( 6 ) types of optical aberrations: 1. Spherical Aberration 2. Chromatic Aberrations 3. Astigmatism 4. Coma 5. Curvature of Field 6. Distortion SPHERICAL ABERRATION  Aberration Geometrical optics predicts that rays of light emanating from a point are imaged by spherical optical elements as a small blur. The outer parts of a spherical surface have a focal length different from that of the central area, and this defect causes a point to be imaged as a small circle. The difference in focal length for the various parts of the spherical section is called spherical aberration Spherical Aberration is found in all lenses bounded by spherical aberration / surfaces. The marginal portions of the lens bring rays of light to shorter focus than the central region. The image of a point in space is therefore not a point, but a blur circle. Spherical aberration is the focusing at the different parts of spherical lens. This aberration occurs because light hitting the outer parts of the lens is bent more sharply and comes to a focus sooner than that passing through the middle. In spherical aberration, the image is blurred because different parts of a spherical lens or mirror have different focal lengths. CHROMATIC ABERRATION Chromatic aberration is the failure of different colored light rays to focus after passing through a lens, focusing of light of different colors at different points resulting in a blurred image. When white light, which consists of colors, passes through a lens, the lens bends the rays. The rays then cross one another on the other side. The violet rays bend more than the other colors and focus close to the lens. The red rays bend the least and focus farther from the lens. Rays on the other colors focus at points between these two points. In chromatic aberration the image is surrounded by colored fringes, because light at different colors is brought to different focal points by a lens. ASTIGMATISM Astigmatism is the defect in which the light coming from an off-axis object point is spread along the direction of the optic axis. If the object is a vertical line, the cross section of the refracted beam at successively greater distances from the lens is an ellipse that collapses first into a horizontal line, spreads out again, and later becomes a vertical line Astigmatism is the failure of a lens to produce a point image of an object point. Such condition occurs when the lens surfaces are not symmetrical with respect to the principal axis of the lens. An extreme example would be one surface is spherical and the other is cylindrical, or when the lens surfaces are perfectly spherical but the beam of light from the object point passes through the lens very obliquely. In astigmatism, the image appears elliptical or cross shaped because of an irregularity in the curvature of the lens. This is the inability of the lens to bring horizontal and vertical lines in the subject to the same plane of focus in the image. COMA The result of differences in lateral magnification for rays coming from an object point not on the optic axis is an effect called coma. If coma is present, light from a point is spread out into a family of circles that fit into a cone, and in a plane perpendicular to the optic axis the image pattern is comet-shaped. Coma may be eliminated for a single object-image point pair, but not for all such points, by a suitable choice of surfaces. A pear – shaped image of small circle or point near the edges of the image plane. Coma occurs when light falling obliquely on the lens and passing through different circular zones is brought to a focus at different distances from the plane film. A spot of light appears to have a tail, rather like a comet. In come, the images appear progressively elongated toward the edge of the field of view. The term Coma was coined 1733 by French mathematician Alexis Clairaut ( 1713 – 1765 ). CURVATURE OF FIELD A curved, concave, or saucer – shaped image of an object which has a flat surface produced by simple lens.  In curvature aberration the relation of the images of the different points are incorrect with respect to one another. In curvature, the images of the different points of the plane image lie on a curved surface, with points at the edge of the field lying nearer to the lens than those at the center. In curvature, the images distance is different for different points of the same object due to their differing distance from the axis. The fuzziness increases toward the edge of the film. Refocusing brings different circle into focus but others now are blurred. DISTORTION Distortion arises from a variation of magnification with axial distance and is not caused by a lack of sharpness in the image. When there exists a different magnification for rays at different angles distortion exists. Any straight light extending across the field is considered curved and for different lenses the curvature maybe from or toward the center. The distortion is called barrel distortion (in the first case). It is the common type of curvilinear defect. The second distortion is the pincushion defect. OTHER OPTICAL DEFECTS These defects are usually corrected when the lens is designed; however, they can occur if the lens is misused or through normal wear. 1. FLARE or OPTICAL FLARE In a result of double reflection from inner lens surfaces. It exhibits itself as a misty haze, or a cloudy semicircular patch of light, which may cover part or the entire image. This doubly reflection may form an image called a ghost image. 2. MECHANICAL FLARE Are bright spots on the film caused by stray light from worn shiny parts of the lens such as the stop, shutter lens mount, or from the camera itself. 3. LIGHT LOSS Most corrected lenses is coated with a substance which will reduce one type of flare ( optical ) and which will also increase the optics ability to transmit light thus reducing light loss. 4. STRAY LIGHT Can be reduced or eliminated by using the proper lens shade placed on the front of the lens as shield. SENSITIZED MATERIAL Sensitized Material refers to films and papers that are composed of emulsion containing SILVER HALIDE crystals suspended in gelatin and coated on a transparent or reflective support. FILM A film consists basically, of a random scattering of light sensitive silver halides suspended in a layer of animal gelatin which is coated onto acetate support or base. THE FILM STRUCTURE A. STRUCTURE OF WHITE and BLACK FILM 1. TOP COATING (TOP LAYER) – scratch resistant coating also called gelatin coating, an over coating composed of a thin transparent layer of a hard gelatin which help protect the silver halide emulsion from scratches and abrasions. The hard gelatin, which is derived from cows, contains SULFUR. The SULFUR is very much compatible with silver halides.  2. EMULSION LAYER – SILVER SALT + GELATIN – A layer composed of silver compounds which are light sensitive and halogens (such as bromide, chloride and iodide bromide in fast film emulsion). A silver compound when combined with a halogen becomes SILVER HALIDE. Silver Halides are rare compound that are responsible in forming the so called the LATENT IMAGE in the photographic film. 3. FILM BASE – commonly made of cellulose or other material such as paper, plastic, or glass, which supports the emulsion layer and is coated with a non-curling antihalation backing. 4. ANTIHALATION BACKING – a black dye applied on the rare surface of the film. Its function is to absorb light that may penetrate the emulsion thus making the image sharper since it suppresses double image. It prevents halo formation in the photograph. The black dye is removed during processing by one of the chemicals in the developer. Its second function is to control the film from curling inwards. (Towards the emulsion surface). B. STRUCTURE OF COLOR FILM 1. TOP LAYER – sensitive to blue light only, green and red light passes through it without exposing the color halide. 2. EMULSION LAYER a. Blue filter b. Yellow filter – CAREY LEA silver suspended in gelatin, it is coated between the top and second layer to absorb any penetrating blue light but allowing green and red light to pass through. c. Green filter – a layer that is orthochromatic, the layer sensitive to blue light (which can not reach it) and green, but not to red light pass on to the bottom of the emulsion layer. d. Red filter – a panchromatic layer, sensitive to blue (which can’t reach it) and red. It is also sensitive to green light but to a slight degree that is insignificant. 3. ANTIHALATION BACKING / COATING 4. FILM BASE – Plastic film base Emulsions are thin, gelatinous, light-sensitive coatings on film that react chemically to capture the color and shadings of a scene. The four layers pictured above show the same image as it would appear on different emulsions in photographic film after the first stage of developing. For black-and-white photographs, only one emulsion is required, because it is the amount of light, not the colour that activates the chemical reaction. Color film requires three layers of emulsion, each of which is sensitive to only one of the primary colors of light: blue, green, or red. As light passes through the layers, each emulsion records areas where its particular color appears in the scene. When developed, the emulsion releases dye that is the complementary color of the light recorded: blue light activates yellow dye, green light is magenta, and red light is cyan (bluish-green). Complementary colors are used because they produce the original color of the scene when the film is processed. Color films are more complex than black-and-white films because they are designed to reproduce the full range of color tones as color, not as black, white, and grey tones. The design and composition of most color transparency films and color negative films are based on the principles of the subtractive color process, in which the three primary colors, yellow, magenta, and cyan (blue-green), are combined with their complements to reproduce a full range of colors. Such films consist of three silver halide emulsions on a single layer. The top emulsion is sensitive only to blue. Beneath this is a yellow filter that blocks blues but transmits greens and reds to the second emulsion, which absorbs greens but not red. The bottom emulsion records reds. When color film is exposed to light by a camera, latent black-and-white images are formed on each of the three emulsions. During processing, the chemical action of the developer creates actual images in metallic silver, just as in black-and-white processing. The developer combines with dye couplers incorporated into each of the emulsions to form cyan, magenta, and yellow images. Then the film is bleached, leaving a negative image in the primary colors. In color transparency film, unexposed silver-halide crystals not converted to metallic silver during the initial development are converted to positive images in dye and silver during a second stage of development. After the development action has been arrested, the film is bleached and the image fixed on it. C. TYPOLOGY OF FILMS Exposure is made simultaneously in the three layers. Each layer responding to only one of the additive primary colors (red, blue and green). After exposure and during the film processing, the yellow color of the filter layer is destroyed.  Films maybe classified according to their forms and types. Basically, films that are available in the markets today are in various forms. They can be in rolls, in cartridges and cut sheets. Light sensitivity of the film can be ascertained through its various types. There are some films that are sensitive to all colors while there is some that are sensitive only to one or specific set of colors. Classification according to USE 1. BLACK and WHITE FILM – for B and W Photography 2. COLOR FILM – films that have names ending in COLOR - Color negatives for prints The negative in this type of film is divided into blocks and is color positive. It is composed of hue dyes. In between the blue and green hues, yellow gelatin is placed so that the blue rays of light would not affect the green hue and in between the green and the red dye, magenta gelatin is placed so that the green rays of light would not affect the red hue dye of the emulsion. 3. CHROME FILMS – films with names ending in CHROME - For color transparency (slides); films that are exposed by slides, mounted in a cardboard for slide projectors: reversal type. 4. X – RAY FILM – films that are sensitive to X- radiations Types based on FILM SPEED (according to light sensitivity) 1. FAST FILM – contains numerous number of large grains of silver halides that usually develop in groups; film that are very sensitive to light. When the available is dim, this type of film is the best choice because of the low reflection power of the subject against a background. It is low in contrast but high in brightness. However, the use of fast speed film is not advisable due to its graininess result. 2. SLOW FILM – film that require longer period of time to completely expose their emulsion to light; film with fine grains of silver halides. Film Speed Film is classified by speed as well as by format. Film speed is defined as an emulsion's degree of sensitivity to light, and determines the amount of exposure required to photograph a subject under given lighting conditions. The manufacturer of the film assigns a standardized numerical rating in which high numbers correspond to “fast” emulsions and low numbers to “slow” ones. The standards set by the International Standards Organization (ISO) are used throughout the world, although some European manufacturers still use the German Industrial Standard, or Deutsche Industrie Norm (DIN). The ISO system evolved by combining the DIN system with the ASA (the industry standard previously used in the United States). The first number of an ISO rating, equivalent to an ASA rating, represents an arithmetic measure of film speed, whereas the second number, equivalent to a DIN rating, represents a logarithmic measure. Low-speed films are generally rated from ISO 25/15 to ISO 100/21, but even slower films exist. Kodak's Rapid Process Copy Film, a special process film, has an ISO rating of 0.06/-12. Films in the ISO 125/22 to 200/24 range are considered medium speed, while films above ISO 200/24 are considered fast. In recent years, many major manufacturers have introduced super fast films with ISO ratings higher than 400/27. And certain films can be pushed well beyond their ratings by exposing them as though they had a higher rating and developing them for a greater length of time to compensate for the underexposure. DX coding is a recent innovation in film and camera technology. DX-coded cartridges of 35-mm film have printed on them a characteristic panel corresponding to an electronic code that tells the camera the ISO rating of the film as well as the number of frames on the roll. Many of the newer electronic cameras are equipped with DX sensors that electronically sense this information and automatically adjust exposures accordingly. Differences in sensitivity of a film emulsion to light depend on various chemical additives. For example, hypersensitizing compounds increase film speed without affecting the film's color sensitivity. High-speed film can also be manufactured by increasing the concentration of large silver-halide crystals in the emulsion. In recent years, a generation of faster, more sensitive films has been created by altering the shape of crystals. Flatter silver-halide crystals offer greater surface area. Films incorporating such crystals, such as Kodak's T-grain Kodacolour films, have a correspondingly greater sensitivity to light. The grain structure of faster films is generally heavier than that of slower films. Grain structure may give rise to a mottled pattern on prints that have been greatly enlarged. Photographs taken with slower-speed film appear less grainy when enlarged. Because of the small size of their silver-halide grains, slow-speed f