A few scanning tips


Yes, you definitely should learn this technique. It's so easy and the results are so good. Why not?

The Histogram is a very standard and very potent tool, but another standard tool is the Curve Tool. This is a more powerful and slightly more difficult tool, but it is a closer representation of how the scanner actually implements all the other tools.

You will notice the Histogram and Curve Tools let us to manipulate the Master Channel (Master meaning the composite of the 3 RGB channels simultaneously), or any one of the RGB channels individually. For example, if you want the reds lighter or darker, but only in the highlights, you can do that by adjusting the tones in the red channel. The main Color Tint tool will affect all tones of the color, where the Histogram and Curve tool can be selective as to tones.

In scanners, the effect of adjustments to these controls is cumulative. You can tweak the histogram Points, and then go tweak the Curve Master channel curve, and then the Green curve alone, and you will get the combined result of all such tweaks. Considerable adjustment runs the risk of hitting the limit which saturates the color. 30 bit and 36 bit scanners offer more range before that happens.

Most scanners also have Auto modes to automatically set the Black and White Points. However, I'd instead encourage you to learn and use the manual procedure above. It's so easy, just click, click, and you can much better react to different photo conditions if you have a little experience with the technique.

The Basics 101 sections describe how video and printers are "different" concerning resolution and image size. Sometimes you can find a compromise so that one image is suitable for both purposes, but it may take two scans and two images for their different requirements.

Scanning B&W photos

It needs to be said that both B&W and Color scanning modes use exactly the same procedure of setting the B&W Points. The histogram is gray anyway, and B&W is simply easier because the color balance is never off. <grin> There really is no difference in the procedure. All of this section applies to B&W too. Line art is of course different.

B&W photos should be scanned in 256 shades of Gray. Setting the B&W Points can be quite dramatic in restoring old faded photos. However, if restoring B&W photos discolored by stains, there are definitely times when it is better to scan them in Color mode. This keeps the colored stain separate. It is easier to touch up to remove a blue stain when nothing else is blue, than if you let it go to gray and blend in with the photo objects. Then convert back to Gray when touchup is complete.

Conversely, color prints to be converted to a Grayscale image are desirably scanned first in color mode. Scanning in Grayscale normally uses only one of the RGB sensors, normally Green (but it is selectable, and often the composite of all three cells is selectable). The Green cell alone is perhaps best for Line art, but it may not scan a color photo perfectly. It may not get red and blue tones just right. So you may prefer to scan color photos in Color mode, and then let the software convert to Gray by computing the Gray tone luminance, just like the Histogram does it.

Copyright © 1997-2010 by Wayne Fulton - All rights are reserved.

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