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An acquired taste by Tim Daly, from Ag29 |
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Colour detection: Film and flatbed scanners are designed with different sensing capabilities. Colour depth, sometimes referred to as ‘bit-depth’ is the first consideration. Just like the range of different colours in an artist’s palette, colour depth defines the maximum number of colours that can be drawn upon when rendering a scanned image. If the range of colour options limits you, then less realistic images will result. As a digital artist, you will need to use a minimum colour palette of 16.7 million different options, (commonly referred to as 24-bit) in order to make a photo-realistic photograph; this 24-bit palette creates three 8-bit red, green and blue colour channels, each with the same range fixed on 0-255 brightness scale. Yet despite the range of the 24-bit palette, many new scanning devices can detect far more than this. Some of the latest budget scanners can be set to operate with an additional 42-bit super sampling setting that can detect billions of different colours, albeit being slight overkill for most desktop inkjet output. As might be expected, these super sampled images create gigantic file sizes and restrict the user to a reduced set of Photoshop’s commands. With the vast majority of output devices, including monitors, unable to display billions of colours, images will need to squeezed back into a 24-bit palette beforehand. You would be very unlikely to see any visible difference between a 24-bit end-result of a 36-bit or 42-bit scan. Dynamic range: This phrase is usually indicated on professional film scanners only and refers to the scanner’s ability to detect detail in both highlights and shadows simultaneously. CCD sensors are more capable of recording simultaneous detail across a wide f-stop range than are conventional films. The process of good scanning involves making an identical copy of your original without losing highlight and shadow detail in the process. For experienced darkroom photographers, this is just like duping or making internegs, where any increase in contrast during translation makes for a worse end result. Next Page >> |
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• Preset scanner settings often present the user with more trouble than they are worth. In this example the same image was scanned as follows: top left: no presets; top right: Auto ‘exposure’ ; bottom left: matched to an Epson 870 preset; bottom right:matched to an Epson 1200 preset. © Tim Daly Page 2 0f 6 |
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