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Scanners

When using a scanner to digitize an image, it is equally important that you maintain shadow and highlight detail. Many scanners offer a histogram that will indicate if shadow or highlight detail has been lost. The features used to adjust the scan will vary from manufacturer to manufacturer, so you'll have to experiment with the features offered in the software that came with your scanner to determine which one will affect shadow and highlight detail. Some scanners are better than others at capturing shadow detail. The darkest shade the scanner can capture detail in without forcing an area to black is know as its D-Max. The higher the D-Max of your scanner, the deeper it can peer into the shadows of an image and still retain detail. So, if you notice that your scanner has trouble capturing shadow detail, you might want to shop for a new scanner that features a higher D-Max specification.

You might need to visit the manufacturer's web site to find out the D-Max rating of a particular scanner (it's not always shown in ads or catalogs). If they don't list the D-max, there's a good chance that it's not that high of a number, so they don't want to admit to a negative by listing it. I don't blame them. It's just like 0-60 MPH ratings in car brochures. You'll find them in sports car brochures, but it is rare to find it listed for an ecomony car.

16-bit images can contain up to 32,769 brightness levels, while a standard 8-bit image can contain a maximum of 256. Those extra brightness levels can help to produce a smoother adjustment result, even though only 256 shades are used to display all images on-screen and when printed.



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