Pre-Press Course Notes JAN 2020 PDF

Nitec in Visual Communication Pre-Press Technology Unit Code: DM3017FP Version: 1.0 Dated: January 2020 1 M6 - Pre-press Technology Content____________________...

Nitec in Visual Communication Pre-Press Technology Unit Code: DM3017FP Version: 1.0 Dated: January 2020 1 M6 - Pre-press Technology Content____________________ Page Chapter 1- Acquire required files................................................................................ 3 Chapter 2 - Halftones............................................................................................... 6 Chapter 3 - Colours.................................................................................................. 12 Chapter 4 - Printing Processes.................................................................................. 23 Chapter 5 - File Formats........................................................................................... 32 Chapter 6 – Copyrights............................................................................................. 43 Chapter 7 - Texts Acquisition................................................................................... 46 Chapter 8 - Layout, design and print job specifications........................................... 57 Chapter 9 - Component of a printed book............................................................... 64 Chapter 10 - Book binding methods........................................................................ 65 Chapter 11 - Folding Schemes................................................................................ 70 Chapter 12 - Correction marks for manuscript mark-up........................................... 77 Chapter 13 - Image Trapping................................................................................... 81 Chapter 14 - Markings for printing and finishing....................................................... 87 Chapter 15 - Imposition layout for offset printing...................................................... 89 Chapter 16 - Print embellishment processes........................................................... 90 Chapter 17 - Art work and layout for restaurant menu............................................. 92 Chapter 18 - Printing Schemes................................................................................. 95 Chapter 19 - Imposition planning.............................................................................. 97 Chapter 20 - DIN Paper Format................................................................................ 99 Chapter 21 - Produce mock-up of print jobs............................................................. 101 Chapter 22 - DTP output devices............................................................................ 103 Chapter 23 - Pre-flight checks.................................................................................. 106 Chapter 24 - Plan and design greeting/invitation cards............................................ 108 Chapter 25 - Specifications for printing jobs............................................................. 114 Chapter 26 - Printing Inks......................................................................................... 117 Chapter 27 - Liaising with the printer........................................................................ 119 Chapter 28 - Print Output (Proofing)....................................................................... 121 Chapter 29 - Factors affecting the reproduction of colours...................................... 123 Chapter 30 - Check print output............................................................................... 124 Chapter 31 - Print adjustments................................................................................. 127 Chapter 32 - Determine print adjustments for the artwork........................................ 130 Chapter 33 - Describe the use of the colour management system............................ 131 Chapter 34 - Perform proofing and checking........................................................... 135 Chapter 35 – Projects............................................................................................... 136 Chapter 36 - Portfolio presentation.......................................................................... 139 Type Gauge........................................................................................... 140 Line Thickness Gauge............................................................................ 141 2 Chapter 1- Acquire required files Define PPI and DPI Define the term Image Resolution Image resolution refers to the spacing of pixels in the images and is measured in pixels per inch(ppi). Resolution is the number of pixels or dots per inch (ppi/dpi). Typical resolution values vary between 72 ppi (pixels per inch) for a computer screen up to 2400 ppi for very high quality professional printing. The higher the resolution, the more detail is stored for the graphic. This means that a higher resolution image is higher quality, but it is also larger in file size. Measure the Resolution of an image The first thing you need to be aware of when dealing with digital images is the resolution of the image. Simply put, an images resolution is determined by how many pixels of information exist per inch within the image at 100 percent of the size it will be printed. Your digital images are very similar to a mosaic made with colored tiles. Pixels are the tiles with which the image is built. The more tiles you can use per inch, the more refined the detail can be within the image. Here's an illustration of the differences you might expect to see in image quality between a 72 pixel per inch image and a 300 pixel per inch image. The image on the left shows a detailed look at what 72 pixels per inch looks like up close. 72 dpi close up 72 dpi image 300 dpi image 300 dpi close up (Smaller in size as compared to an 300 dpi image) 72 pixels per inch is considered low resolution although it is perfectly fine for a website or other on-screen display, it is not really good enough for a high-resolution image setter which will reproduce your artwork to be printed on a printing press. The 300 pixel per inch image has over three times as much detail. When working with images destined for a printing press you should be using a general rule of thumb of 2 to 1. The digital image should posses twice as many pixels per inch as the line screen in which your artwork will be printed at. So Cal Graphics likes to print images at 175 line screen or 150 line screen. So, using the 2 to 1 rule, your images should be scanned at 350 or 300 pixels per inch for maximum quality. Any less than that and you risk having the golfer on the left in your foursome. When in doubt, you should be safe saving your images at 100% of the size they will print, CMYK (or grayscale if you are printing 1 color), 300 pixels per inch for photos and 600 pixels per inch for hard-edged line art, and in TIF format. There are different types of resolution in computer graphics. Monitor image resolution is measured by something called PPI (pixels per inch). Printed image resolution is measured by something called DPI (dots per inch). DPI is the more common term and is often used interchangeably with PPI when 3 referring to on-screen images. An image that has 72dpi contains less information than one that is 300dpi. There are two different levels of resolution that a designer might use; monitor resolution and printing resolution. Measure an output device resolution Printing resolution means how clearly an image will print on a printer or in professional printing uses where the images are printed on paper. Laser printers and inkjet printers used to output film for professional printing require more information than is available in a 72dpi file to produce a smooth and clear image. How much more depends on the bit depth of the image. To scan an image in higher resolution than 300 dpi (Dot Per Inch) is for example in most cases unnecessary if you are going to print the image on an ordinary laser printer. The image quality will not improve in printing; it will just take longer to print. What you see on-screen is not necessarily what you'll see on the printed page. Black and white (1-bit) bitmap images are actually pretty easy to understand in this regard. A designer doesn't need any more resolution in an image than the resolution of the final printing device. This means that, if the image is being final printed on a 600dpi laser printer (a cheap flyer perhaps), the images need resolution of 600dpi at 100%. Grayscale and colour bitmap images (8–32-bits) are a little more tricky. One needs to know how the image will be output and at what halftone screen (linescreen) ruling before scanning an image. The line screen refers to the number lines (of dots) per inch (lpi) that will be used to simulate tones of colour and gray in the printing process. A typical line screen for a laser printer is 85 lpi. A newspaper's screen is usually between 85 – 120 lpi and a magazine is often between 133 and 150 lpi. A bitmap image's resolution should be twice the linescreen. In the case of a laser printer, an image would require 170 dpi for the best appearance on a printer using 85 lpi. A color magazine would require an image be 300 dpi for best reproduction at 150 lpi. Anything less will cause an image to deteriorate and pixelate. The amount of the deterioration depends on how much lower the resolution is than what it should be. Image Resolution Identify the relationship between an Image’s Resolution and an Image’s Print Size The most important thing to understand about resolution is the relationship between an image's resolution (ppi) and an image's print size (actual width and height). Image Resolution is represented by dpi. Dpi stands for dots per inch. It means the number of dots of information or pixels that are stored in a given file. A picture is made up of many pixels. 4 A digital image consists of a number of picture elements, known as pixels, which carry information about the colour and tonal values required at a particular location in an image. Images are made of picture elements or pixels, which are little squares of colour. All factors being equal, the larger the number of pixels in an image, the higher the quality and the more defined that image is. Realistically, pictures will be of different sizes; a small image may have few pixels and a large image many pixels. This does not mean that the larger image has higher quality. It is the density of pixels that impacts quality and file size. This is most often referred to as pixels per inch (ppi) and is the resolution value. Since pixels are the building blocks of our image, their size depends on output dimensions. In other words, the larger the final print, the fewer the number of pixels per inch (ppi), and the greater their actual size. The quality of an image therefore suffers if the amount of pixel information is insufficient for the reproduction of fine colour and tonal gradations. 360dpi 60 dpi These two images above give some idea of the difference in quality obtained from the same size print at two different resolutions. The first one represents 360 ppi, the second 60 ppi. The latter is clearly blurred, but it is surprising how low a resolution is possible before differences are perceived by the naked eye. Generally, however, more pixels per inch mean more detail and more subtlety of color. When an original image is resized, the number of pixels present in the original scan remains the same, regardless of changes to the overall output size of the image. For this reason the number of pixels per inch will decrease when an image is enlarged, and increase when image size is reduced. 5 Chapter 2 - Halftones Picture images has to be converted into halftones to be able to be printed. These halftone pictures consisted of dots of different sizes to reproduce the printed picture details. In the reproduction of a colour picture, four halftone images are used. Various methods of image display/presentation Pixel A pixel, named after a pix (like "pic" from picture) element, is the smallest unit on a display screen or monitor. A pixel defines a small, rectangular part of the image. Each pixel has a color and an optional opacity value. Pictures are displayed on monitors by dividing the monitor up into rows and columns of pixels. The more pixels that are squeezed into a monitor's surface, the smoother an image will appear on screen. Pixels are so close together that it appears that they are connected to your eye. A monitor with more pixels per inch (PPI) will be more expensive than a cheaper monitor. Pixels are the fundamental units of Photoshop. When you edit an image, you change the value of the image's pixels. Pixels have no size or shape. On the monitor, each image pixel outputs a square beam of light. Each pixel can only have one color or tone. Halftone screen A black and white photograph may have hundreds of shades of gray. A colour photograph may have upwards of three million colours in it, but most printing presses use only these four process inks: - Cyan - Magenta - Yellow - Black Black-and-white printing requires only black ink. To get various shades of gray to reproduce an image, we use a process called screening. Screening breaks an image into a series of dots. Varying the dot sizes approximates shades of color. In a black-and-white photograph, for example, a group of large dots placed closely together appears black. A group of smaller dots with larger spaces between them produces a weaker, gray shade. A group of even smaller dots spaced widely apart appears almost white. The term ‘Halftone Screen’ refers to a pattern of tiny dots that is used for printing an image to simulate continuous tones. An image which is formed by using dots of various sizes and shapes. In printing, continuous-tone art (such as a photograph) is reproduced using halftones, which are either created by photographing the original artwork through a screen or by manipulating the image on a computer. Halftone screening has to be used for image reproduction (print). An image consists of different colours and different shades. All printing processes could only lay down a standard layer of ink on the 6 paper surface. The halftone screen helps to break the images into dots which when combined and viewed together, reproduces the endless combination of different mixed colours, tones and shades. Halftones screen dots has to be small enough so that when the picture image, viewed at the reading distance will produce the optical illusion of a sharp image with good details and different colours and shades. The halftone dots could come in different shapes, depending on the purpose and end use. Conventional halftone Screen Rather than use an actual photo as a sample, a step wedge similar to the top picture is best used as a reference containing obvious (stepped) tonal variations. The second picture is a halftoned representation of the step wedge. The darker the image, the larger the halftone dots become up to and beyond a point where the dots begin to (virtually) overlap. C=75° K =45° C =75° 75°0 K= 45° M= 15° M =15° Y=0 Y= 0° ° Enlarged image of a 4-colour C CMYK halftone screen angles Halftone print Each halftone colour screen is assigned a screen angle so that they are evenly distributed/spaced out. The use of a wrong screen angle for any colour will cause a conflicting visible pattern known as moiré. FM Screen FM screening keeps the dots the same size and varies the frequency, or number, of dots and the location of those dots to simulate the original image. This illustration shows enlarged simulations of FM screening. 7  FM Screening Sample You can see from these illustrations that, regardless of the type of screen employed, the eye perceives a shade of gray depending on the percentage of ink coverage. In FM screening, the concepts of screen angle and frequency no longer apply. Because the dots are randomly placed, there is no direction (the screen angle used in AM screening) to the dots. The variable spacing of the dots means there is no fixed spacing, and therefore there is no screen frequency. Who Can Benefit from FM Screening… Applications for FM screening span the industry: newspapers, magazines, commercial printers. The key to successful use of any FM screening technology is summed up in one word: control. The user who successfully controls the production environment can realize the considerable benefits of FM screening. In FM screening, the dots produced on the plate imagesetter is very fine. The printing machine must be in very good condition in order to print and reproduce the images onto the paper. Magazines Magazines with in-house image setting operations can use FM screening to produce high-quality colour. Once the dot gain calibration has been performed in collaboration with the printer for the press, paper, and ink, the magazine can use these settings for every production run. Newspapers Newspapers can also use FM screening to good advantage. Newspaper industry tests with frequency modulated screening show higher quality color and image detail than with conventional screening, due to the relative coarseness of the conventional screen used with newsprint. Newspapers can output pages more quickly at lower resolutions -- high enough to satisfy typographic quality requirements -- and the colour images will be of much higher quality than if conventional halftone screening were used. Screen Frequency § Screen frequency, also called screen ruling or halftone dot frequency, refers to the number of lines per inch of halftone dots. It is also referred to as dots per inch – dpi. 8 § The same two factors also affect the number of gray levels or colour tones available, measures of the tonal depth in the final image. § The screen ruling used to image films or printing plates for a job depends on the resolution of the imagesetter/platesetter and on the paper stock and type of press used to print the publication. § A newspaper is commonly printed using a low screen ruling of 85 lpi because newsprint’s high absorbency of ink and the high speed of the press. § A higher screen ruling would saturate the newsprint with ink and make the images look muddy. § A four-color magazine printed on coated paper might use a screen ruling of 150 – 175 lpi, with art magazines using up to 300 lpi. Lower screen rulings make images appear coarse and less detailed. § Screen ruling also determines the size of a halftone cell, which in turn dictates the maximum size of a halftone dot. The halftone dot is made up of printer dots; printer resolution determines the number of dots available to create the halftone dot. § As the screen ruling increases, the size of the halftone cell decreases; fewer printer dots are used to create the halftone dot, so fewer graduations can be represented and the image may lose depth. The lower the screen ruling, the larger the halftone cells; the higher the screen ruling, the smaller the halftone cells. § Halftone-dot percentages are measured with densitometer – an instrument for measuring the relative density of any part of an image. § In a process that expands 50% mid-tone dots into 70% dots, the 70% kind will only grow into ones that are about 85%. Larger dots are augmented by less than the full twenty points, in this case by only about fifteen points and the same is true for those smaller than mid-tone as well. 9  Dot gain on coated stock Dot gain on uncoated stock Dot gain on newsprint Good halftone Halftone dots printed on uncoated and Dot newsprints paper reproduction Commom Screen ruling used in commercial printing Normal coated smooth paper - 60 lines/cm (300 lpi) Uncoated paper – 54 lines/cm – (133 lpi) Newsprint paper – 35 lines/cm – (90 lpi) In DTP, the resolution of the images to be printed is always set at 300 dpi Effects of screen ruling on different types of paper and dot gain The type of paper and paper quality is an important factor in determining your screen ruling frequency. If the paper is porous, dot gain will obviate any detail that could be gained from using a high screen frequency. Papers and coatings come in a large variety of types and are intended for many different purposes. Newsprint A coarser paper made mostly from wood pulp and highly porous. It is manufactured almost exclusively for printing newspapers. The dot gain for newsprint can be as high as 30% or more. Uncoated Paper Any number of different types of uncoated paper. Dot gain for uncoated paper is roughly 20%. Expect a few percent variation either way depending on how fast the press is run and how subject the press is to regular minor adjustment by the operator. In general, sheet-fed presses run more slowly than web-fed presses, which in some cases may facilitate control. Coated Paper Paper surfaces are been given a chalk coating during paper manufacturing, It helps to seal the paper surface and produce a less porous and smoother finish. The dots printed on this paper will not be absorb into the material and expand in size. On a sheet-fed press, the dot gain on coated stock can be as low as 10%, although 15% is probably more typical. High- quality grayscale and four-color images are usually printed on coated stock. Supercalendered Paper Calendering freshly made paper is analogous to ironing cloth. It is a normal finishing step involving heat and pressure. Supercalendering is done for some 10 papers in order to get a smoother, less porous surface. Supercalendered paper can be coated or uncoated. Uncoated Supercalendered stock can have a dot gain approximately as low as ordinary coated stock. 11 Chapter 3 – Colours RGB stands for the colours Red, Green and Blue. RGB are the colours that computer monitors, scanners and televisions use to show colours. Pictures taken by a digital camera and saved as an image file (jpeg format) is in RGB. The images are viewed on the computer screens or other display devices in RGB mode. When working in RGB colour, you are working with 3 colour channels. Each primary colour, red, green and blue, has its own channel, and the intensity of each channel, on a scale from 0 to 255, contributes to the colour per pixel. Think of it as like mixing paints. The proportions of red, green and blue used on the painter's palette create a colour. If a warmer shade is desired, more red is added, with less green and blue, etc. But since white is a pure colour, it is created by combining each channel at full intensity (255). Colorus are created in the RGB mode by assigning values ranging from 0 to 255 for each of the color channels. The overlapping areas represent the colors created by full values for each channel, in this case creating cyan, magenta, yellow, and white. CMYK Colours/Process Colours CMYK stands for the colours cyan, magenta, yellow and black. (in order to avoid confusing black with blue, its abbreviation is K instead of B). CMYK are primary colours used for four-color commercial printing. They are also known and subtractive primary colours. If you look at a magazine close up you will see 12 the image is made up of tiny patterns of dots, these dots are arranged in different patterns and sizes to fool the eye into seeing colours that are not really there, e.g. brown etc. Colour pigments are used to make the four colours inks - Cyan, Magenta, Yellow and Black. They are printed in patterns of dots which our eyes “mix” to create the illusion of many different colours. When outputting to inkjet printers, although inkjets use CMYK printing, it is best to keep your images in RGB. Ink jets do their own conversion to CMYK in the printer. If you convert to CMYK before sending to print on an inkjet, the printer will convert it to RGB and then back to CMYK. CMYK are the primary colours used in printing. CMYK used in printing is subtractive. (The colours “subtract” white from the printed surface.) While in theory, cyan, magenta and yellow could reproduce any colour; black is added to compensate for some impurities of the inks. Black colour also enhance the picture details in the shadow areas and make the picture more contrasting. Process colour printing - CMYK refers to the printing inks used in four-color process printing. Cyan, Magenta, Yellow and Black are the colours used to produce full-colour photographs and designs. - Process colours are transparent colours. - When cyan and yellow are overprinted together, green colour results. Cyan Magenta Yellow Black These process colours can be combined and printed to emulate a wide number of other colours. If you look carefully at a printed colour photograph in any magazine or book, you'll see that it's made up of rows of tiny dots called a halftone screen. The dots work together, at different angles, to fool your eye into seeing a full spectrum of colours. For a graphics file to be printed in CMYK, it must be converted or created in that colour mode. When film or plate is produced, a different sheet of film or plate is created for each colour. For the computer to tell the machine that produces the film, an imagesetter, what to output on each sheet of film, the computer image must be in CMYK format. Colours in a page layout program must also be specified in percentages of the four coloured inks. Printing an image in full-colour is a complicated process involving a number of steps. A basic knowledge of these steps is not only essential for printers, but it is also important for designers in planning and creating the best layouts and for print buyers in understanding some of the issues that are raised when purchasing colour work. What Is "Four Colour Process"? It is the most common colour system for print, producing full colour. The vast majority of magazines and colour books are produced using four- colour process. 13  Originally the artwork and originals were separated photographically using filters to produce four printing plates. Today's separation and production is carried out digitally. The four ink colours are Cyan, Magenta, Yellow and Black - often referred to as CMYK. A mistake often made when submitting artwork for 4-color printing is not converting the images to the CMYK colour space. This is needed so that the file can be separated into the four colours (see example) so that a separate printing plate can be made for each of the colors. Also Known As: 4-colour | process colours Duotone Duotone mode is very similar to grayscale. Duotones are used when you want to add some depth or colour to a black and white image, or just get a trendy effect. A duotone lets you choose 2 ink colours on your image and will print as a 2 colour job on the press. Usually, it will be made up of black and one other colour, though it doesn't have to be. There is also a Tri-tone - which has 3 colours and a quad-tone that has 4. You can produce some very sharp black and white (Grayscale) images with this and it is used very often for printing photography books. Duotone Mode allows you to confine the colour range of an image to one colour (Monotone), two colours (Duotone), three colours (Tritone), or 4 colours (Quadtone). Dutton have one channel, so however many colours you use by choosing Duotone, Tritone, etc. you will only have 256 levels. Duotone image will cut down the printing cost as its only consists of two printing colours. Pantone/Spot Colours/House Colours printing process Sometimes, specially mixed colours have to be used to print a colour. These are specially mixed colours that are not reproduceable from mixing the normal CMYK inks. These colours are often used as “house colours” for printing company logos or colours on printed materials. These colours usually have to be specially mixed and printed as a colour on its own. Spot colour inks come in all types of colours and shades, including some specialty inks such as metallic and flourescent. Spot colour is useful for documents that require only a few colours, such as newsletters, brochures and stationery. Spot colour is also used to match specific colours very closely. Spot colours are pre-mixed and use one ink for each colour in the publication. There are different brands of spot colour inks. In the United States, the dominant spot colour printing system is PANTONE. The Pantone Matching System or PMS consists of over 1,000 colours of ink. Pantone is a patented system with printed colour sample swatches on different types of paper for mixing and matching colours. Print designers use these printed colour swatches to select the desired colours. Printers use these swatches to check the accuracy of the reproduction of the colours on the final print out. 14 Also Known As: PMS colors Specialty inks can also be used as a spot colour to provide even greater emphasis to an area. Specialty inks can range from fluorescent, fade resistant, opaque, and metallic inks. A Look at Spot Colours It's a good example of a Web graphic that would use spot colours when it's printed. There are essentially three colours in the above graphic: Pantone Colours System The colour mixing and matching system of Pantones To ensure that a printer uses exactly the colour that a designer intends, colour systems were developed. The most common of the spot colour standards is the Pantone Matching System or, PMS as it is more commonly known. All of the modern image-editing, vector-drawing and page-layout programs come with a full library of thousands of Pantone colours as part of the program. In addition, designers will want to have a set of swatch books that show printed examples of the colors and their codes. Swatches are a more reliable method of matching or choosing colours than doing so on-screen. This is because monitors are illuminated by light behind them which makes colors seem brighter on- screen than they are when printed on paper. Also, colours on a monitor are created with red, green and blue light (RGB) rather than mixed ink pigments. In some cases, both spot colour and process colour can be used on the same document. For example, a company brochure may include colour photos (process colour) and a corporate logo (spot colour). Spot colour applies a pre- mixed ink to the page. This colour is usually identified by a colour system such as the Pantone Matching System. Your printer or designer will often refer to a specific colour using a 'Pantone number'. If you are going to talk about colours in this context, you need to know a few basics. 15 The PANTONE MATCHING SYSTEM® is the definitive international reference for selecting, specifying, matching and controlling ink colours It is used by artists and commercial printers to select, specify and match colours very precisely. Many logos are created with specific PANTONE Colours that can be very closely reproduced. By using PANTONE Colours, designers can be confident that their output will match their expectations. Each Pantone number relates to a unique colour in a colour palette. It is not always possible to accurately match a 'Solid' colour by mixing cyan, magenta, yellow and black so a compromise is therefore necessary. Pantone produce colour guides to deal with this issue. The Solid to Process Guide shows each Pantone 'Solid' colour and its nearest 'Process' colour equivalent. Before actually printing with colour, it is necessary to understand some of the factors that influence the appearance of colours on a printed document. Listed below are some of the important points to consider: Although colour guides are a good tool for determining the colour that should be used, (such as spot colours), they should be used only as a guide. There is no guarantee that the final printed colour will look exactly like the colour in the guide. The colours in the guides tend to fade, so the guides are usually valid for about a year. The colour swatches in a guide are usually printed with a saturation that may be hard to achieve on some applications. The type of paper on which colour is printed has a huge affect on the way the colour appears. The same colour will appear to be quite different when printed on coated and uncoated papers. The ink absorption rate, along with the brightness and the colour of different papers can result in significant changes in the way colour appears on different papers. There can be differences in ink pigments between different ink manufacturers, which is another reason why it is difficult to perfectly match the colour in a guide. Most printers use ink from one vendour, so they can usually expect consistency in the ink they use. Lighting conditions affect the appearance of the ink colour. Differences in daylight during different times of the day and differences in artificial 16  illumination, such as fluorescent and incandescent, can cause a wide shift in the appearance of a colour. Precise colour matching can only occur when the preceding factors are considered. A colour viewing booth can be used in order to accurately match the printed colour with the proof. Lighting conditions, materials, and the techniques used, must be controlled in order to achieve the best results when printing with colour. Colour Separation Process For a graphics file to be printed in CMYK, it must be converted or created in that colour mode. When film is produced, a different sheet of film is created for each colour. For the computer to tell the machine that produces the film, an Imagesetter, what to put on each sheet of film, the computer image must be in CMYK format. Colours in a page layout program must also be specified in percentages of the four coloured inks. Image 2 - (Above) A typical Imagesetter device. In order to reproduce or prepare a full colour image for printing using four process colours, the image must be divided into the individual subtractive primary colour components. The separation process can be accomplished photographically or electronically. Photographic Separations: Using a large process camera, a full colour image is converted into halftone negatives which contain a series of dots of various sizes to represent shades of gray. This method is hardly used today because it takes a lot of time to produce just one set of colour separation films. It is also very difficult to control the quality of the output. Electronic Separations: The electronic separation of an image into its individual colour components has become the most popular and labour saving method of producing colour separations. The separations can be produced from an image produced with analog methods, such as photography, or from a digitally generated image. When producing separations from an image produced with analog methods, the image is first placed in a scanner, which converts the image into a digital record. The digital image can then be imported into an image editing software program where the colour separations can be produced with the click of a mouse. The scanned image and/or the colour separations can be quickly manipulated and edited in an infinite number of ways with the tools provided with the software. Colour separations can also be produced from digitally produced images, such as from a digital camera or images composed entirely in design or illustration software on a computer. Digitally produced images eliminate the scanning step from the workflow. 17  Colour separations created electronically can be output to - film to prepare analog plates through a film imagesetter - offset plates through a plate imagesetter (Computer-to-Plate). - digital printer to produce as digital printing output. Image 3 - (Above) Colour Separations and their negatives which produce the final image, (middle left). Compare the Differences in the Separation Process for Conventional Printing and Digital Printing Years ago, being a printer meant having offset printing presses. Today it also means having digital printing equipment and high-speed copiers. The Conventional Printing process uses the CMYK system with printing plates created using film negatives or electronic PostScript files. Each of four printing plates is inked with one of the four process colors, and the ink is transferred to paper in layers. Film negatives are created from digital files. Images from the negatives are transferred to printing plates in much the same way as photographs are developed. A measured amount of light is allowed to pass through the film negatives to expose the printing plate. When the plates are exposed to light, a chemical reaction occurs that allows an ink-receptive coating to be activated. This results in the transfer of the image from the negative to the plate. 18  Image 4 - (Above) Colour Negatives are "stripped" together for each page. Color and registration control is a process that is aided by the use of computers. Registration is the alignment of the printing plates as they apply their respective color portion of the image that is being printed. If the plates do not line up perfectly, the image will appear out of focus and the color will be wrong. A computer takes a video image of registration marks that have been placed on the press sheet. Each plate has its own individual mark. The computer reads each of these marks and makes adjustments to the position of each plate in order to achieve perfect alignment. All of this occurs many times per second while the press is running at full speed. Image 5 - A blue-line print is made from "stripped-up" negatives and is used to check the image position before printing. Digital Printing is the use of digital technology to do printing. Today printing can be done in the home with the use of printers attached to the personal computer. The appropriate software can be used to do relatively good quality printing from the comfort of one’s home. Basically, when in comparison to conventional printing processes, there are no intermediate pre- press processes between the digital document file and the final print. No films, imagesetters, plates, platesetters, photochemicals and no waste. Digital offset printing is very popular for short run jobs where the speed of a press is not needed. Digital printing has been replacing Analog Printing since the early 1990’s. At first it took off slowly; however, it has proceeded to the point that in 2000 there were a lot of major players in the industry. Existing technology companies such as Xerox, IBM, and Canon who were already leaders in the photocopying, photo and other parts of the already elaborate digital world entered into the digital printing industry with consummate ease. Across the Atlantic in Europe, Heidelberg was already creating digital copiers and presses so that by the 2001 Printing Expo in Chicago there were already quite a few companies involved in displaying their products. 19 Outline the Method of Colour Reproduction using Printing Press and Digital Printer Colour reproduction with Digital Printing normally makes use of cyan, magenta, yellow and black (CMYK) toners, jets of ink or solid inks. Six- and even 12-color digital printers which try to give more accurate tones and colour reproduction through the use of extra colors are also becoming popular. As with plate-based printing, dots of the different colors are combined on the paper to produce almost any group of colours. Digital printing, however, cannot usually feature metallic colours without using a completely separate process (such as screen printing) to overprint the printed pages. Colour matching tends to be more difficult with digital printing, especially if you want to match a Pantone colour. Expert calibration of the printing equipment is necessary, as is control over environmental factors such as heat and moisture. Solid areas of colour also need to be checked carefully on digital prints because they have a greater tendency for unevenness of tone. We know that Cyan, Magenta, and Yellow are the three main pigments used for color reproduction. When these three colours are combined on the printing press, the result should be a reasonable reproduction of the original, but it is not. Due to limitations in the ink pigments, the darker colours are dirty and muddied. Images 6 & 7 – Photo in RGB (above) (Below) converted to CMYK, notice the slight colour difference To resolve this, that’s why the black separation is also created, this improves the shadow and contrast of the image. Some printers have five- and six-colour presses, so you can combine full colour process colours with extra Pantone colours. You might do this if you were producing a publication that featured full colour photographs and also a metallic colour. 20 Compare spot colour and CMYK process, its advantages and limitations Design choices will affect cost! The cost of printing colour documents is usually related to the number of ink colours used. As process colour requires four or more inks, spot colour can be cheaper if you use fewer than four colours. Spot colour also has the advantage of printing a wider range of clean, bright colours. If a colour seems smooth and even no matter how closely you look, it's probably printed with spot colour. Cons & Pros of spot colours If a designer needs to match a particular colour (a logo colour perhaps) in a printed piece or has a limited budget, then spot colour is something to consider. Spot colours can also be used alongside process (CMYK) colours for greater flexibility. Though some may view spot colour printing as being much more limited than CMYK printing, there are many interesting possibilities. Two or more spot colours can be mixed to create interesting colours and effects. Spot colours can be combined to create duotones, tritones and quadtones that can be very effective and can add some visual interest to otherwise grayscale images. Unfortunately, it's difficult to proof spot colour jobs. Most proofing systems use CMYK-based technology. Some laminated proofs, which work by attaching coloured sheets of clear acetate, have some spot colours available but these are often expensive. You can create the illusion of more colours in a job by using shades of your PMS colours: these are known as screens, shades, or tints. For instance, the golf ball in the GolfScapers logo has gray in it. This is a shade (or tint) of black. Full Colour Printing Vs. Spot Colour Spot colour printing is not like full colour process printing. In full colour process printing, four primary colours (cyan, magenta, yellow & black) are used offering hundreds of thousands of possible combinations to create full colour printing. 21  In spot colour printing, single colours of ink are used that limit the possible colour combinations to those specific inks. For example, if you had a spot colour job that was being printed in green ink, the only variations in colour you will see is where the ink has been "screened" to give the appearance of a lighter shade. If you are printing with two colours, you are limited to those two colours and the lighter shades available through screening those two colours. 22 Chapter 4 – Printing Processes You can choose from several different processes to print a publication or print products. The method you choose depends on: your budget, urgency required print volume type and end-use of the printed substrates/materials, final expected/required print results, type of embellishment, choice of a commercial printer. The various printing processes used for the production of printed materials for various uses and application are: 1. Offset lithography 2. Letterpress 3. Flexography, 4. Gravure, 5. Screen printing 6. Digital printing 7. Pad printing The different printing processes has its different characteristics, print results, advantages and disadvantages. When used correctly it can produce very good results suitable for the desired end-use. 1. Offset Printing/Lithography Offset lithography is one of the most popular printing process used in commercial printing today. Offset printing is also known as lithographic printing. Unlike other types of printing, offset lithography involves printing from a flat surface plate. Most of the plates used in offset printing is made of aluminium. The image and non-image areas lay on the same level. It works on the principle that ink (oil) and water do not mix. The image areas take on the oily ink and repel the water. The non-image areas take on the water and repel the ink. During the printing process, the printing plate is first dampened with water to keep the non- image areas clean. The image areas are then inked up for printing. The inked-up images of the plate (which is mounted on a plate cylinder) are then transferred onto the blanket cylinder. The inked images on the blanket cylinder is then transferred and printed onto the paper on the impression cylinder. A multicolor offset press has a separate printing unit for each colour ink being printed. If, for example, you’re using 4 process colours and one spot colour in a print job and your commercial printer’s press can handle five inks, a printing unit will be set up for each ink. The paper will then pass through the 5 printing units in succession. If the printing press handles fewer inks, the printer will print two or three inks first, stop the press and change the inks and then run the paper 23 through the printing press again the second time to print the remaining inks. Offset printing is widely used for printing because of its high-speed printing capability. It could also reproduce very fine image details and good colour reproduction. It could also be used for printing very good results on paper with rough/textured surfaces. Most companies are also using the time and labour saving Computer–to-Plate method to produce their printing plates. The make-up pages or designed jobs in DTP are directly sent to the laser imagesetter to produce the offset plates. Offset printing could be done on a sheet-fed or web- fed machine. Which type of machine to use depends on the types of jobs. Sheet-Fed Offset Printing § With sheet-fed offset you can print almost any paper-based printed product. As the name indicates, printing is done indirectly on paper sheets. § Offset printing is an indirect printing process using a blanket cylinder to transfer the printing ink from the printing plate to the paper surface. § This method allows for an enormous selection of paper in terms of both finish and quality. § Some machines are equipted to do in-line aquaous and spot coating during the printing process § A wide range of high-quality after-press processing is available for sheet-fed prints, including lamination and glue binding of the printed product. § Common sheet-fed products include advertising brochures, annual reports, posters and books, as well as, other high quality printed products. The Sheet-Fed Offset Printing Press In the foreground, you can see the delivery bay where printed sheets are collected as they come out of the press. The four separate printing units (one for each color) are visible in the background. 24 Print Paper Dryer Unit Print Coater Colour Printing Paper Feeder Inspection Delivery Unit Unit Units Unit Table A 6-colour sheet-fed offset printing press with coater and dryer unit Web-Fed Offset Printing § Web-fed offset printing is usually used for production of prints that are time- sensitive with short turn-around time e.g. newspapers, magazines, etc. § The paper is fed into the machine from a paper roll/web. § It is most suitable for large-volume editions – for example, 50,000 units and above. Common web-fed offset products include newspapers, periodicals, folders and other prints of lesser quality. 25 2. Letterpress In Letterpress printing, the relief print image areas are higher than the non- image areas. Traditionally, the image carrier (printing form) is made of lead types, zinc blocks and dies. Copper and brass blocks are used for embossing. This printing method is not used for printing of books and ,magazines as the print image quality is not so good as compared to offset. It is also comparatively tedious to prepare the printing forme. It is very widely used for special printing process of die-cutting, foil embossing and relief embossing. It is also used for numbering of commercial forms. It is not commonly used for printing nowadays because of its comparatively lower print quality and slower printing speed. Paper Impression Inking Cylinder Rollers Printing Forme A Letterpress machine used for die- cutting work Letterpress die-cut formes 26 3. Flexography It is also a relief printing process similar to letterpress printing. However, the image carriers (printing forme) are mainly made of rubber or thermoplastic, which are comparatively flexible, mounted on a forme cylinder. Flexography is mainly used in the packaging industry for the printing on cartons, corrugated boards, tissue, napkins and shopping PVC carrier bags. The printing process is also used for mass production of stickers and labels. The inks can be formulated and adapted to print on different materials – paper, corrugated boards, PVC, cloth, etc. The printed materials are usually printed as a continuous web. The quality of the printed image is comparatively low. However, it has the advantage of printing at a relatively high speed in web on different types of printing materials. Inking Roller Relief Forme Paper s Cylinder Impression Cylinder 4. Gravure Printing Gravure is a relatively expensive process. It is a direct printing process. The printing images are etched or engraved into the surface of a copper printing cylinder. During the printing process, the printing cylinder is dipped into the relatively liquid solvent ink. The excess ink on the non-image areas surface is removed by a metal strip known as the doctor’s blade. The print materials are usually printed in web form. Solvent inks are formulated to suit different printing materials – paper, plastics, PVC etc. The quality of the printed image and colour reproduction consistency is very high. Gravure printing is used for printing packaging materials and high volume magazines. It is also used for printing wall paper because of its’ “endless” print capability. The image on the printing cylinders could be prepared to print images on web materials without visible image break. Because of its’ relatively high cost in producing the printing cylinders and its special printed image characteristics, it is used for printing currency notes, bonds and share certificates. 27  Impression Cylinder Paper Print Form Cylinder Doctor’s Blade Ink Trough 5. Screen Printing (Silk) Screen printing method made use of an image carrier which essentially is a frame mounted with a fine nylon or steel mesh. The image carrier is prepared by coating a light- sensitive coating on the mesh. After exposing the image on the mesh using a film negative, the print image is developed. The printing/image areas on the screen mesh allows ink to pass through. The non-image areas are closed and prevent ink from passing through. This principle of the printing form can be adapted for printing cylindrical shapes – e.g. glass bottles. Different types of inks can be formulated to suit the different print materials. Traditionally, it has been widely used for printing textiles. Screen printing was widely used for printing large advertisement panels before the advent of digital printing. It is used for printing book covers, spot coating, cloths, T-shirts, bottles, plastic drums. It is widely used in the electronics manufacturing industry for the production of printed circuit boards (PCB). Inking Squeegee Image Carrier (Screen) Paper 6. Digital Printing § In digital printing, presses are connected to workstations that create PostScript® files from digital files, screen bitmap images, and send the files to the press. The presses do not require film or, in some cases, printing plates. § Some digital presses transfer digital information onto electro photographic cylinders instead of plates and use toner to print four-color pages. Other presses send the digitized pages directly to special plates mounted on the press. 28 § Most digital printing systems use laser to generate and produce the print images § Digital printing produces fast turnaround times, low production costs, and the ability to easily personalize publications. § It is often used for on-demand or short-run colour printing, where only a small number of copies are printed. § Digital printing produces fast turnaround times, low production costs, and the ability to easily personalize publications. § It is often used for on-demand or short-run colour printing, where only a small number of copies are printed. § It is not suited for high-volume, high-quality print jobs. § The image sharpness, colour rendering and resolution are still not as good as offset printing. Digital Sheet-fed Presses High-speed digital press 29  Digital Press Other digital output from digital pre-press Image setters § An image setter generally works like a laser printer, but instead of printing on paper with coloured powder, photosensitive film or paper is exposed and developed. These films are then used to produce images on the offset plates for offset printing. § An image setter usually has a higher resolution than a laser printer – around 3600 dpi, compared to 600 dpi for an average laser printer. It’s because the emulsion side of the film has a high resolution. § In laser printers, the ink toner/powder and paper type limit the resolution. § An image setter exposes film, but you also need to develop the film after it had been exposed. These machines are called online film processors. § The image setter’s RIP (raster image processing) calculates the halftone screens, creating a large bitmap in which every exposure dot in the image setter is represented by a one or a zero. If you’re printing multiple colors a separate bitmap is created for each component color in the print. § There are also image setters that output to printing plates instead of film. They work in a way using a technique called CTP. Image setter By looks the image setter is anonymous. On the right, the exposed film is fed forward into a developer – so called online development. Computer-to-Plate Imagesetting 30 § Computer-to-plate (CTP) image setters, also called direct-to-plate image setters, work like film image setters except that laser diodes image dots onto an aluminum or polyester surface rather than a piece of film. § This eliminates a costly and time-consuming step on the way to press. CTP image setters also often produce higher print quality by avoiding multiple generations of film processing. § CTP image setters accept PostScript files and produce large format proof sheets digitally. Because digital proofs don’t allow proofing of traps and changes are extremely costly, CTP imagesetting is best used when the publisher has full confidence that the files being handed off to the printer will not require changes. 7. Pad Printing Pad printing is also known as tampon print. This printing process does not traditionally belong to the printing industry. It is usually found in the manufacturing industry. The print image is engraved on a copper plate. During the printing process, the engraved (sunken) image is filled with printing ink. The excess ink is scrapped off by a doctor’s scrapper blade. The ink on the engraved image is picked up by a pad, made of silicon rubber and transferred onto the surface of the object to be printed. During the printing process, the mounted image plate move together with the printed object. Different type of inks could be mixed and formulated to suit different types of printed materials. This printing process could be adapted to print different objects of different shapes and sizes. Pad printing method is commonly used for printing small items with irregular surfaces - machine labels, wave-band lenses of radios, electrical and electronic appliances, small gift and souvenir items (like pens) etc. Printing Pad Doctor’s Scraper blade Image plate Print Object 31 Chapter 5 – File Format Define the term vector and raster graphics This chapter describes some of the most common graphic file formats for image files, as well as how to determine which file format to use for Web graphics. When you save your image to a specific file format, you are telling your applications how to write the image’s information to disk. The specific file formats you choose depends on the graphics software application you are using (e.g., Freehand, Photoshop) and how and where you will use your image (e.g., the Web or a print publication). There are two types of computer graphics – raster and vector. The raster graphic is composed of pixels and vector graphic is composed of drawing paths. 1. Vector graphics Vector graphics are made up of lines, curves, circles and shapes etc, defined by mathematical objects called vectors. By following these instructions, the computer can create the variety of elements needed to form the shape of all objects in the image. For this reason, vector graphics are often called object-oriented graphics. These graphics retain their crispness whether they are resized, moved or have their colour changed. Vector graphics are appropriate for illustrations, type, and graphics such as logos that may be scaled to different sizes. Compared to raster images only the formulas are stored. This makes the size of the file very small. The images don't loose focus when you zoom, since the lines are re-rendered. A vector image gives a very high quality, it requires small storage space and is easy to edit. That's why you should always try to save your vector images in a vector format. It is not possible to save photos, scanned images etc in a vector format. Examples of vector images are drawings, diagrams and illustrations. 32 Picture 1 Enlargement of a vector image. The quality is still good. Picture 2 Enlargement of a vector image. 2. Raster graphics A raster image is made up by small dots, known as pixels in different colors. Each pixel is assigned a specific location and colour value. The dots create a pattern which forms an image which we called a bitmap (this is why raster graphics are also called bit-mapped graphics). In working with bitmap images, you edit groups of pixels rather than objects or shapes. The pattern will show if you take a very close look at the image. Picture 3 Enlargement of a raster image. Picture 3 Enlargement of a raster image. The quality is not improved. Drawings, photos, images etc, which shall be used in a document need to be transformed into a digital format. This is done by scanning the image or takes a photo with a digital camera. The image is then stored as a raster file, i.e. dot- pattern image. Differences between raster and vector graphics Computer graphics can be created as either raster or vector images. Raster graphics are bitmaps. A bitmap is a grid of individual pixels that collectively compose an image. Raster graphics render images as a collection of countless tiny squares. Each square, or pixel, is coded in a specific hue or shade. Individually, these pixels are worthless. Together, they're worth a thousand 33 words. Raster graphics are best used for non-line art images; specifically digitized photographs, scanned artwork or detailed graphics. Non-line art images are best represented in raster form because these typically include subtle chromatic gradations, undefined lines and shapes, and complex composition. However, because raster images are pixel-based, they suffer a malady called image degradation. Just like photographic images that get blurry and imprecise when blown up, a raster image gets jagged and rough. Why? Ultimately, when you look close enough, you can begin to see the individual pixels that comprise the image. Although raster images can be scaled down more easily, smaller versions often appear less crisp or "softer" than the original. To maximize the quality of a raster image, you must keep in mind that the raster format is resolution-specific -- meaning that raster images are defined and displayed at one specific resolution. Resolution in raster graphics is measured in dpi, or dots per inch. The higher the dpi, the better the resolution. Remember also that the resolution you actually observe on any output device is not a function of the file's own internal specifications, but the output capacity of the device itself. Thus, high resolution images should only be used if your equipment has the capability to display them at high resolution. Better resolution, however, comes at a price. Just as raster files are significantly larger than comparable vector files, high resolution raster files are significantly larger than low resolution raster files. Overall, as compared to vector graphics, raster graphics are less economical, slower to display and print, less versatile and more unwieldy to work with. Remember though that some images, like photographs, are still best displayed in raster format. Common raster formats include TIFF, JPEG, GIF, PNG and BMP files. Despite its shortcomings, raster format is still the Web standard -- within a few years, however, vector graphics will likely surpass raster graphics in both prevalence and popularity. Vector Graphics contains drawing directions, Raster image is not like drawing a circle etc. scalable. The image degrades when it is scaled 1. Unlike pixel-based raster images, vector to larger size. 34 graphics are based on mathematical formulas that define geometric primitives such as polygons, lines, curves, circles and rectangles. Because vector graphics are composed of true geometric primitives, they are best used to represent more structured images, like line art graphics with flat, uniform colors. Most created images (as opposed to natural images) meet these specifications, including logos, letterhead, and fonts. 2. The major advantage of vector graphics over the bit-mapped format is that vector graphics look the same, even when you scale them to different sizes. In contrast, raster graphics tend to become ragged-looking when you change their size. On the other hand, only raster graphics can reproduce photo-realistic images. 3. The vector format has two big advantages over raster graphics: (1) vector graphics area quickly and perfectly scalable, i.e., they can be can be resized and stretched without distortion; and (2) vector graphics files are usually much smaller than bitmap files and thus use less memory in storage and less bandwidth in transmission. This makes them ideally suited for the World Wide Web. 4. Further, unlike raster graphics, vector images are not resolution-dependent. Vector images have no fixed intrinsic resolution, rather they display at the resolution capability of whatever output device (monitor, printer) is rendering them. Also, because vector graphics need not memorize the contents of millions of tiny pixels, these files tend to be considerably smaller than their raster counterparts. Overall, vector graphics are more efficient and versatile. Common vector formats include AI, EPS, FH, SWF, WMF etc. 1. Vector graphics are resolution-independent—thus, their resolution is determined only by the output device. Because vector elements are mathematically-defined, scaling (enlarging or reducing their size) simply requires modification of their component mathematical descriptions. 2. Whereas vector graphics are resolution-independent, raster images are resolution-dependent—the number of pixels that occupy a given space must be defined. Consequently, raster image resolution is specified in pixels per inch (ppi). However, although the term is not effective, image resolution commonly is referred to in dots per inch (dpi)—dpi more appropriately is attributed to device resolution or output resolution, where the number of dots an output device is able to produce within an inch represents the resolution of the device. Identify the various vector and raster graphic formats 1. Vector Graphics Formats Some common vector graphic file formats are listed below. Common Vector Graphics Formats File Proper MIME type Description Extensions name Application/ Adobe.ai Vector format for Adobe Illustrator. illustrator Illustrator 35  Document A PostScript file that describes a small vector Encapsulated.eps Image/eps graphic, as opposed to a whole page or set of PostScript pages. Macromedia Application/.fh Freehand Vector format for Macromedia Freehand. Freehand Document Application/ Flash Source Shockwave Flash source file, only usable by.fla Flash File Macromedia Flash authoring software. Fully supports vector graphics in a de facto standard format which can be read and Portable printed on almost all operating systems. A Application/.pdf Document much simplified version of PostScript allowing pdf Format for files containing multiple pages and links. Works with Adobe Acrobat Reader or Adobe eBook Reader. Generic vector-based page description language, created and owned by Adobe. Application/.ps PostScript Postscript is a powerful stack-based postscript programming language. Supported by many laser printers. Flash is a web page plug-in that displays Application/ vector based animations contained in SWF.swf shockwave- Flash files. Several applications can create SWF flash files; these include the Flash authoring tool from Macromedia. Stores vector graphics and raster graphics as Windows a sequence of commands to be issued to the.wmf Image/wmf Metafile graphics layer of the Microsoft Windows operating system. (only partially vector) Some file formats, e.g. PDF, allow both raster and vector graphics. This is because the underlying PostScript system of the Portable Document Format is designed to handle both methods of creating graphics. 2. Raster Graphics Formats Some common raster graphic file formats are listed below. Common Raster Graphics Formats file MIME type proper name description extension Commonly used by Microsoft Windows programs, and Windows the Windows operating system itself. Lossless.bmp Image/bmp Bitmap compression can be specified, but some programs use only uncompressed files. GIF is used extensively on the web. Supports animated images. Supports only 255 colors per Graphics frame, so requires lossy quantization for full-color.gif Image/gif Interchange photos (dithering); using multiple frames can Format improve color precision. Uses lossless LZW compression, that used to make GIF avoided sometimes due to patent issues concerning LZW. JPEG is used extensively for photos and other Joint continous tone images on the web. Uses lossy Image/jpg Photographic.jpg compression by trying to equalize eight by eight Experts Group pixels; the quality can vary greatly depending on the 36  compression settings. PNG is an image format with lossless compression, Portable offering bit depths from 1 to 32. It was mainly.png Image/png Network designed to replace the use of GIF on the web. Free Graphics of the patent, which expired in 2003, associated with GIF. Default proprietary format for Adobe Photoshop Application/ Photoshop documents. Has many extra features such as image.psd Photoshop Document layering. Supported by very few image editing programs other than Adobe Photoshop. TIFF is used extensively for traditional print graphics..tiff Tagged Image Image/tiff Lossy and lossless compression available, but many File Format programs only support a subset of available options. Advantages and Disadvantages of Vector and Raster Graphics Vector graphics have three distinct advantages over bitmapped graphics. - Vector graphics are more flexible than bitmapped graphics because they look the same even when you shrink or enlarge (scale) them to different sizes. In contrast, bitmapped graphics become jagged when you scale them. - Vector images also look better on devices (monitors and printers) with higher resolution, whereas bitmapped images always appear the same regardless of a device's resolution. - And finally, vector images often require less memory than bitmapped images. The various portable file formats used in the Print Industry Image file formats that we use most frequently in the printing industry are TIF, EPS and PDF. Either one is suitable and both have distinct technical advantages for advanced computer users. If you are manufacturing a "cutout" or "clipping path" in an image program like Adobe Photoshop® its typical to save the image as an EPS file since an EPS file format is used to deal with path data commonly called "vector" art. Adobe Illustrator® and Macromedia Freehand® files must be saved as EPS format files for this same reason. You may find that a TIF format is a little easier to work with. Characteristics of these formats JPEG (.JPG,.JPEG) JPEG compression economizes on the way data is stored and also identifies and discards extra data, that is, information beyond what the human eye can see. Because it discards data, the JPEG algorithm is referred to as "lossy". This means that once an image has been compressed and then decompressed, it will not be identical to the original image. In most cases, the difference between the original and compressed version of the image is indistinguishable to the eyes. In general, compressed JPEG images have compression ratios of between 5:1 and 15:1. A trade-off does exist between the image quality and the amount of compression. You do not need to decompress images saved in the JPEG format. They are automatically decompressed when they are opened. 37 TIFF - Tag Image File Format The TIFF (Tagged Image File Format) is a raster (bitmapped) file format. Almost every raster program, such as an image editing or paint program, can save TIFF files. and almost every other application can place or import TIFF images. These files are extremely flexible – a TIFF can be CMYK, RGB, grayscale, index, or bitmapped format, any bit depth and any resolution. TIFF is also a good format for files that need to move between Windows and Macintosh computers. TIFF Compression Compression means the information in a file is squished so the file takes up less disk space. When you save a TIFF file, you are given the option to apply LZW or ZIP compression. These compressions are “lossless”. It means that no data is lost when the file is compressed so that the image looks exactly the same when it is compressed as does when it is not compressed. You are also given the option to apply JPEG compression which is lossy. TIF (file extension, pronounced Tiff) Its main strengths are a highly flexible and platform-independent format, which is supported by numerous image-processing applications. TIFF is the format of choice for archiving important images. TIFF is the leading commercial and professional image standard. TIFF is primarily designed for raster data interchange. The most common file format that popular imaging applications support, and not to forget the printing industry, is TIFF. TIFF supports most color spaces, RGB, CMYK, etc. You can save both RGB and CMYK files in TIFF-format and TIFF is supported both by Mac and PC. TIFF is a flexible format with many options. All major programs today can read TIFF either way, and TIFF files can be exchanged without problem. A TIFF format is complex, so TIFF files are generally larger than GIF or JPEG files. TIFF supports lossless LZW (Lempel-Ziv Welch) compression; however, compressed TIFFs take longer to open.. Lossless means there is no quality loss due to compression. Lossless guarantees that you can always read back exactly what you thought you saved, bit-for-bit identical, without data corruption. This is a critical factor for archiving master copies of important images. Most image compression formats are lossless, with JPG and Kodak PhotoCD. PCD files being the main exceptions. Compression works by recognizing repeated identical strings in the data, and replacing the many instances with one instance, in a way that allows unambiguous decoding without loss. This is fairly intensive work, and any compression method makes files slower to save or open. It is not necessary to say much about TIF. It works, it's important, it's great, it's practical, it's the standard universal format for high quality images, it simply does the best job the best way. Give TIF very major consideration, both for photos and documents, especially for archiving anything where quality is important. But TIF files for photo images are generally pretty large. Uncompressed TIFF files are about the same size in bytes as the image size in memory. Regardless of the novice view, this size is a plus, not a disadvantage. Large means lots of detail, and it's a good thing. 24 bit RGB image data is 3 bytes per pixel. That is simply how large the image data is, and TIF LZW stores it with recoverable full quality in a lossless format. When saving a file to the TIFF format, add the file extension ".tif" to the end of its file name. 38 Description Name: Tag Image File Format Extension: TIF, TIFF Type: Raster format Colors: 1 to 24-bit Color Spaces: Grayscale, RGB, CMYK Versions: 1–6 (1992) Compression: LZW (Lempel-Ziv-Welch), JPEG or Uncompressed Standard: Adobe Platforms: DOS, Windows, Macintosh and UNIX Others According to the standard all import filters for TIFF should support the LZW-compression. Purpose Platform independent format for photos etc. TIFF has become a defacto-standard for raster images. PDF – Portable Document Format PDF stands for Portable Document Format. As the name implies, it is a data format that can be used to describe documents. Adobe, the developers of PDF, market software to create, edit and visualize PDF files. Because the specifications of the file format are publicly available, a lot of other companies develop software for PDF as well. In prepress, PDF is used more and more as a format to exchange data between applications. PDF files can contain text, images and tables such as those produced by spreadsheets. Many documents are based on standard paper sizes such as A4 and so can be readily printed. However, the PDF format will handle documents up to five metres square and so can accommodate the largest maps and plans. The use of word processor files such as Microsoft Word is not a real option for the publication of material since not every one uses it and for even Word users the output from a given file is just too dependent on version of the software and the printer used. Similarly, publication using web pages is not always a satisfactory option because what the reader sees depends on his browser and monitor resolution. Of course Apple Macintosh computer users don't use Windows at all but happily the same PDF file works for Apple computers as well as for Windows machines. The PDF format is therefore well worth consideration by local historians looking for an alternative means of publishing their work This might be in the familiar format of a printed article but it could be an analysis performed using a spreadsheet, a listing of the contents of a database or a map. This note provides links to some of the many resources on the Internet concerning PDF files. PDF supports security. The creator of a PDF file can set various security options. It is possible to lock a PDF so it can only be opened with a password. It is also possible to forbid changing the content of a PDF or disable the option to print a PDF file. PDF files are not meant to be edited. Small changes can be made to a PDF file but it is virtually impossible to add complete blocks of text or images to an existing PDF file. Description Name: Portable Document Format Extension: PDF Type: Page description language, Meta format Compressions: JPEG, ZIP 39 Application: Adobe Acrobat Platform: Mac, PC, Unix, Linux Purpose PDF is produced by Adobe Acrobat or other applications with add-ons. The format is based on PostScript (PS) format. A cross application and platform description and publishing format. EPS - Encapsulated PostScript Encapsulated PostScript language file. This is a very universal format that can contain both vector and bitmap graphic images. EPS files can be opened in Corel Draw, Adobe Illustrator, Photoshop (the image is rasterized as opened), Freehand and other programs (MAC or PC). The EPS file format can be used for vector images or bitmap images and on a variety of platforms, including Macintosh and Windows. When you place an EPS image into a document, you can scale it up or down without information loss. The PostScript language, which was developed by Adobe, is the industry standard for desktop publishing software and hardware. EPS files can be graphics or images of whole pages that include text, font, graphic, and page layout information. When saving a file in the EPS format, add the ".eps" file extension to the end of its file name. Description Name: Encapsulated PostScript Extension: EPS, EPSF and EPSI Type: Meta format Versions: Level 1 and Level 2 Compression: LZW Standard: Adobe Platforms: DOS, Windows, Macintosh and UNIX Overview EPS is actually a page description language but is also used for describing images. Some software can print but not display the EPS images on the screen, since the software are not able to interpret the EPS information. But it is able to send it to a Postscript printer. There are actually two images in one file, one Postscript image and one low resolution image (e.g. TIF) that is used for preview. Purpose A Platform-independent printing format. EPS should not be used for screen presentation since the low-resolution image is not always displayed correctly. 40 The advantages and disadvantages of these formats Before you save an image in an image processing application (or scan system), you should make a decision on the file format you want to choose. The advantages and disadvantages of the different file formats are described below. Important: Again, the file formats have to be judged from different points of view. Some characteristics of a given file format may be advantageous in general and for OPI processes but - at the same time - disadvantageous with regard to color matching. TIFF Advantages TIFF files can be edited by all popular image processing applications. TIFF files are independent of the output device. For TIFF files, portions of an image can be sent to the output device (in case you have selected only a specific part of the image in the layout application). The resolution of TIFF files can be reduced during output and thereby adapted to low-resolution output devices. The TIFF format supports many color modes. Platform independent (DOS, PC, Mac and UNIX) The format is supported in almost every image and word processing software. TIFF is one of the most common formats. Disadvantages Clipping paths you have applied to the image in an image processing application are usually not preserved for printing Large images require large storage space and takes a long time to download. EPS Advantages Clipping paths that have been defined in image processing applications are preserved for printing EPS has been a de facto standard within the graphic industry during the last fifteen years and offers a very good printing quality EPS is mostly used for storing vector information, which makes small files. Disadvantages Many image processing applications cannot re-edit EPS files. Complete images are sent to the output device, even if you have selected only parts of the images in the layout application. 41  The generation of EPS files may already involve a given output device. In that case, printing to different printer types produces different results. The resolution of an EPS file remains unchanged (e.g. 1200 dpi) even if you are printing to an output device that only allows lower resolutions (e.g. 300 dpi). Thus, printing may become very slow. There are sometimes problems when printing these files on printers that don't support the Postscript format. PDF Advantages Very good printing quality. De facto standard in desktop publishing. A PS-file can easily by converted into Acrobats PDF-format. It is a cross platform standard. This means that somebody can create a PDF file on a Unix workstation and you can open it on a Mac or PC and still see the document just like it was intended to be viewed. PDF files can be device independent. This means that a PDF file can be printed on a cheap ink jet printer. This does not necessarily mean that the output will be optimized for each device. A lot depends on the way the document is created. PDF files are compact. PDF supports a number of sophisticated compression algorithms as well as a clever file structure to keep the file size of PDF files down to an absolute minimum. PDF files can contain multimedia elements like movies or sound as well as hypertext elements like bookmarks, links to e-mail addresses or web pages and thumbnail views of pages. Disadvantages PDF is a proprietary file format. PDF tries to be everything to everybody, meaning that it may not be as efficient for a specific task than a tool optimized for that task. You can use PDF on the Internet but in most cases an HTML document may be more efficient. You can use PDF to exchange small graphic elements like ads, drawings or pictures but more prepress applications can handle the EPS file format. Very limited options to edit a PDF-file. To Sum up on Image Formats When in doubt, you should be safe saving your images at 100% of the size they will print, CMYK (or grayscale if your printing 1 color), 300 Pixels per inch (ppi) for photos and 600 pixels per inch for hard-edged line art, and in TIF format. 42 Chapter 6 - Copyrights What is Copyright? Any item or creative work that is produced by any person or persons is deemed to be protected by copyrights or intellectual property rights. Examples of creative works: - Softwares - Photographic images, films, video images - Drawings, images and graphics designs - Writings, books - Music lyrics - Music scores - Songs - Creative works of art Copyright is designed to protect the copyright holder by preventing unauthorized copying. The copyright holder may issue rights to the item which will determine how you may use it, for how long, in what way etc. All the different parts of a multimedia production may be protected by copyrights. You should assume that unless a right has been specifically granted, you do not have it, and not assume that a work is in the public domain. With text based works ‘fair use’ was often cited as a defense for using work without permission, but in the multimedia environment, this may be harder to define. Moral rights must also be considered. Moral rights refer to the right to object to changes that could harm the author’s reputation or ‘derogatory treatment’. Software § The copyright for software is generally handled by a single company, but it is possible that several copyrights exist. A license granting you permission to use a piece of software does not mean you can distribute it. § When buying an authoring system software for example, you should always check these rights. Some companies allowed unlimited distribution of runtimes; other may require you to pay a separate licence fee for each runtime that is distributed. Photographs § Photographs may involve several layers of copyright, for example, the photographer, the subject of the photograph and the photograph itself. Studio or user may need to pay royalty fees or permission of the photo models to use their pictures for commercial purposes (advertisements). There are photographs or other images that could be bought on-line or from photo CD which assign the rights to buyer to use the pictures and images for the buyer’s purposes and use. § Some images are sold with specific condition that alterations of the image is not allowed or that the images may be used for a specific number of times only. However, such condition is very difficult to monitor. § Scanning a photograph or pictures from books or other publication may also be a breach of copyright. There are many sources of photographs, including 43  commercial photo libraries and public domain sources, internet sites which are copyrights free. Getting Clearance § When seeking clearance, you should clearly define what you intend to use the work for, and what rights you are seeking. Getting too narrow a clearance may mean having to pay extra later, whereas too wide means you may be paying for extra rights that you do not need. Copyrights owner may grant permission for the use of their materials with the condition that the user may need to quote the source or provide an acknowledgement of the copyrights owner. § You should also make clear any changes you intend to make, in case, there are any objections. § Payment may be a one off fee, which is easy to administer, royalties based on sales income, or ‘pay per use’. § In many cases, the method will be determined by the copyright holder. However, where copyright holders have no policy about granting rights, you may do well to write to them, stating exactly how you intend to use their work and what you think is a reasonable payment. The Copyright Policy Guidelines for Various Materials – Web Catalogue, CDs, Print Image Catalogues General Guidelines § Users may use portions of lawfully acquired copyrighted works in their academic projects, with proper credit and citations. They may retain them in personal portfolios as examples of their academic work. § Users must include printed materials that their presentation has been prepared under fair use exemption of the Copyright Law and are restricted from further use. § Users may claim fair use for their own productions providing these productions are: - For face-to-face curriculum-based instruction - Demonstrations of how to create multimedia productions - Presented at conferences (but you may not share copies of the actual production) - For remote instruction as long as the distribution signal is limited - Kept for only 2 years § Fair use ends when the owner/creator loses control of his product's use, such as when it is accessed by others over the Internet. § Users need not write for permission if their presentation falls within the specific media fair use guidelines; however, "users are advised to note that if there is a possibility that their own educational media project incorporating copyrighted works under fair use could later result in broader dissemination, whether or not as commercial product, it is strongly recommended that they take steps to obtain permissions during the development process for all 44  copyrighted portions rather than waiting until after completion of the project”. Web Catalogue § Internet resources often combine both copyrighted and public domain sites; therefore care should be used in downloading images and texts from any sites for use in publication or presentations. § Until further clarification, educators and students are advised to write for permission to download and use Internet resources and to be mindful of the copyright ramifications. Print Image Catalogues § A photograph or illustration may be used in its entirety. § No more than 5 images of an artist's or photographer's work. § When using a collection, no more than 10% or no more than 15 images, whichever is less. What items may not be reproduced or copied. Paper currency notes Passports, NRIC Postal Stamps, Value stamps, cheques, Vouchers, tickets, etc Bonds Certificates, etc Reproduction of any form of such items is forbiddened. Reproduction of these items without permission of the owners is a criminal offence of forgery that has very serious consequences. The person could be prosecuted and charged in court, fined and sentenced to prison. Special written permission may be granted to reproduce the images of such items with conditions that: - user may reproduce and display only partial p