The Eye and the Camera: An Overview

The Eye and the Camera

• The camera resembles the eye more than any other man-made instrument
• Eyes function similarly to a camera
• Eyes' evolution is organic, while cameras' is electrical
• Both the eye and camera have a lens
• The eyelid represents a camera's shutter
• The pupil is like a variable aperture stop or diaphragm
• The retina refers to a light-sensitive surface

Camera

• "Camera" originates from the Latin word for "Chamber"
• Serves as a "light-tight box"
• Focuses images using a pinhole or lens
• Features a shutter to control light exposure
• Houses a holder for sensitized material
• A device to capture images of objects

Evolution of Camera: Essential Parts

• Light Tight Box: Functions as a light-proof enclosure and frame
• Lens: Collects or focuses reflected light to form an image on film
• Shutter: Controls the duration of light exposure on the film
• Holder of Sensitized Material: Secures sensitized material to prevent blurring
• Viewfinder: Determines the field of view or coverage of the lens

Light Tight Box

• An enclosure that prevents light exposure
• Protects the sensitized material inside the camera
• Does not have to be permanently light-tight
• Film must not be exposed to unnecessary light before or after exposure

Lens

• Focuses light rays from the subject
• Sharpens the image projected onto the sensitized material
• Elaborate lenses have multiple glass pieces in a "lens barrel"

Lens Types According to Shape

• Convergent/Positive/Convex Lens: Thicker in the center
• Light converges to a point on the opposite side
• Produces a real image on the opposite side
• Divergent/Negative/Concave Lens: Thinner in the center
• Light diverges as if from a single point
• Produces a virtual image on the same side

Focusing

• Adjusts the distance to create a sharp image

Methods of Focusing

• Scale Bed or Focusing Scale: Uses a scale on the lens barrel indicating preset distances
• Object distance is measured, estimated, or calculated
• The lens is adjusted using a marker to match the object's distance on the scale
• Rangefinders
• Ground Glass
• Zone

Rangefinders

• Measures the angle of light convergence with two apertures
• Split Image: Image is split when out of focus, aligning when in focus
• Used in police work for fingerprints and questioned writings
• Coincident/Double Image: A doubled image indicates defocus, adjusting to coincide brings focus

Ground Glass

• Focus by observing the image on ground glass behind the lens
• Adjust until the image is sharp

Zone

• Applicable to wide-angle lenses
• Uses close (3-6 ft), medium (6-15 ft), and distant (15 ft to infinity) settings

F-Numbers or F-Stops

• Measure the light-gathering power of the lens
• Regulated by a "diaphragm"

Depth of Field

• Measures the acceptable focus zone, from the nearest to farthest object in focus

Depth of Field Factors

• Increased by: Shorter focal length, Small lens aperture, Greater subject distance
• Decreased by: Longer focal length, Larger lens aperture, Shorter subject distance

The Circle of Confusion

• Describes image "sharpness"
• The goal is for every point on the subject to be a point in the image

Depth of Focus

• Refers to how far the film plane can shift before the image blurs
• The film plane is fixed in well-built cameras

Hyperfocal Distance

• Closest distance focused at infinity for maximum depth of field
• Setting the lens to this maximizes the depth of field

Classification of Lenses According to Focal Length

• Focal Length: Distance from the lens's optical center to the film plane in millimeters

Lens Types Classified by Focal Length

• Wide-Angle Lens: Focal length less than the negative material's diagonal
• Short focal length (14mm–35mm) provides a wide view with low magnification
• Normal Lens: Focal length approximately equal to twice the negative material's length
• 45-55mm lenses are considered normal, 50mm is common for general use
• Long or Telephoto Lens: Focal length more than twice the negative material's diagonal
• Offers a narrow angle of view
• Used for surveillance due to magnification from a distance
• Zoom Lens: Variable focal length
• Allows quick focal length changes, useful in sports photography

Wide-Angle Lens Characteristics

• Reduced scale, increased area coverage
• Greater depth of field with less focal length
• Suffers distortion at the edges
• Reduced illumination towards the edges

Fisheye Lens

• A wide-angle variant with up to 180-degree view
• Focal lengths of 8mm and 10mm
• Records the entire sky when pointed upwards
• Produces unavoidable image distortion

Normal Lens Characteristics

• Provides realistic views
• Minimal distortion
• Fewer lens defects

Long or Telephoto Lens Characteristics

• Decreased depth of field
• Increased scale, reduced area coverage
• Less than 45-degree angle of view
• Reduced image quality, especially with motion

Inherent Lens Defects

• Spherical Aberration: Light refracts differently near the center versus the edge
• Results in a fuzzy, distorted image
• Coma (Lateral Spherical Aberration): Light at an angle focuses at different points
• Forms a blurred, comet-shaped image
• Chromatic Aberration: Lens fails to focus all colors at the same point
• Causes color fringing
• Curvature of Field: A curved lens distorts the image into a curved plane
• Astigmatism: Light focuses into lines or ellipses instead of points
• Distortion: The shape of the image changes due to focal length differences

Distortion Types

• Positive (Pincushion): Image points displace outwards
• Negative (Barrel): Image points displace inwards

Lenses Corrected by Degree

• Achromatic: Corrected for chromatic aberration
• Rapid Rectilinear: Corrected for distortion
• Anastigmat: Corrected for astigmatism
• Apochromatic: Corrected for astigmatism with higher color correction
• Aspherical: Corrected for spherical aberration

Shutter

• Device to block light and expose material for a set time

Shutter Types

• Central Shutter: Located within the lens, action moves from center to side
• Focal Plane Shutter: Near the focal plane, often cloth, and moves vertically or horizontally

Shutter Speed

• A selector controls exposure time
• Common speeds: 1, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000

Shutter Speed Settings

• B-Setting: Shutter stays open while pressed
• T-Setting: Shutter opens with one press and closes with another

Holder of Sensitized Material / Film Holder

• Located at the back of the camera
• Secures material and contains a film cartridge and take-up spool

Other Camera Parts

• Viewfinder/Viewing System: Shows scene to be recorded; SLR types display what the lens sees
• Film Advancer: Moves exposed film to take-up spool and prepares next frame
• Lens Aperture: Controls light-gathering power, adjusted via f-numbers
• Shutter Speed Selector: Regulates light by controlling shutter speed
• Focusing Mechanism: Sharpens objects

Camera Accessories

• Tripods: Supports camera, avoids shake, locks composition
• Cable Release: Fires the camera from a distance, prevents movement
• Flash Units: Synchronized light source, effective in low light, captures movement
• Light Meter/Exposure Meter: Measures light for correct exposure
• Extinction Meter: Estimates light from shadows
• Photoelectric Meter: Converts light to electrical energy for measurement
• Extension Tubes: Close-up photography, increases lens-film distance, no glass elements
• Camera Grip: Stabilizes the camera, attached to the body
• Lens Hood: Prevents flare from extraneous light, screwed onto the lens

Filters

• Medium that transmits and absorbs light wavelengths
• Made of glass or gelatin, block certain colors
• Used in black and white photography

Filter Types

• Correction: Changes film response for accurate colors, use "indoor" film in daylight
• Contrast: Alters relative brightness, enhances tonal differences
• Haze (UV): Reduces atmospheric haze
• Neutral Density: Reduces light without altering color
• Polarizing: Reduces reflections

Four Camera Types

• Viewfinder: Smallest, simplest, inexpensive, allows focus in low light, suffers parallax
• Single Lens Reflex (SLR): Views and focuses through the taking lens, eliminates parallax used in police work
• Twin Lens Reflex: Uses a mirror and two lenses, suffers parallax errors with reversed image
• View or Press Camera: Sophisticated, largest, large format, no parallax, bulky, used for document reproduction