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So selecting images is important, although it rarely presents too much of a problem. The next stage is harder – reproducing the images in the best way. The process can be highly complex, and therefore certain measures have to be taken before the images are ready for print.
The basic task once the images have been chosen is to transfer them onto the computer digitally. Or scan them in, as we say in the trade. Scanning varies depending on the original image. A picture taken using a digital camera is already in digital format, usually in RGB (a colour system referring to the primary colours red, green and blue), and there-fore does not need to be scanned in. It is, however, important that the digital image has a high enough resolution – i.e. sufficient pixels (from the term ‘picture element’) – for good reproduction in print.
If the image has to be digitised from a transparency or paper copy, it has to be scanned in using an image scanner, such as a drum scanner or flat-bed scanner. And as with digital images, the original must be scanned in with a high enough resolution for the best possible print quality. Above all, there are two factors that guide the resolution: the screen ruling and the size of the image in print. This also places demands on having a good scanner as the scanner’s resolution capacity affects how much the image can be enlarged.
Image resolution is also partly determined by the paper, as the appropriate screen ruling varies for different paper grades. However, this is normally of little significance.
i A good starting point is to select a resolution that is twice the screen ruling, while also taking into account the enlargement or reduction of the original image. |
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i = ARCTIC PAPER RECOMMENDS
A picture speaks a thousand words, as the cliché goes. But is it true? Well, true or not, few would dispute the fact that images are an extremely important and central part of the graphic production cycle. In other words, the choice of images is important and should not be taken lightly. Images in combination with the paper quality are very much the “first impression” of a printed product.
i Generally speaking all images and especially colourful ones, are well suited to uncoated paper, although extensive adaptation to the paper is necessary if the images are heavy and dark. |
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It is essential to perform some form of image processing in order to achieve optimal image print quality. Quite simply, the image should be adjusted to make it better.
Fundamentally though, even before you begin you should be clear on how you want the end result to be perceived, and what the printed product should convey.
Processing an image in such a way that it turns out exactly like an original photo in printed format – or even gives a true representation of reality and real colours, for that matter – is however not theoretically possible. This is because there is a great difference between how many colour shades the eye can distinguish and what can be shown on a computer monitor or in print. An eye, for example, can distinguish 15-20 million colours, while the figure for a screen is somewhat lower at 10-15 million. It is even lower in printing. On coated paper approximately 6,000 colours can be shown, and on uncoated around 4,000. On the other hand, the eye can be deceived into perceiving the image as identical to the original, and this is something that well-executed image processing can effectively help achieve.
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Colour range
This diagram illustrates the range of colours various media can distinguish.
Image processing is usually done in several stages and involves several tasks – the image is trimmed, the resolution set, and the levels, balance, colours, brightness and contrast are adjusted, before liberating and manipulating the image where appropriate.
i When printing on uncoated paper, there are a few recommendations that should be followed. As the CMYK process colours look slightly duller when printed on uncoated paper, it is a good idea to increase the colour saturation a little. The contrast of the image should be increased slightly.
A good tip for printing on uncoated paper is also to reduce contaminating colours, especially black and blue in reds and oranges, and black and red in greens. Doing this correctly eliminates the risk of orange looking brown, and crisper, clearer green colours are produced.
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