For those of you not going away this weekend, I thought I would pass on the first of a series of tips I have learned along the way. If you have been following my blog, you know that I do a lot of scanning. Scans require correction. Today I want to focus on “how to convert raw scans to pure black and white”.
The picture above shows a “raw” RGB scan of a pencil and marker drawing I showed you previously.

If you choose “Image –> Adjustments –> Replace Color, you will find that you have a whole gamut of colors to convert to either black or white (this is often a problem in converting print ads, the black ink has all kinds of colors in it). The picture below shows purple showing up in the scan.

The solution “begins” with converting to greyscale. Choose “Image –> Mode –> Greyscale”

I say “begins” because, If you chose to use replace color on a greyscale image, you get a simple slider that adjusts ALL pixels at once!

Either towards “Black”…

or “White”!
Not what we want. IMMEDIATELY convert the greyscale back to RGB.
Choose “Image –> Mode –> RGB (Red, Green, Blue)”

Now choose “Image –> Adjustments –> Replace Color” and use the “eyedropper” to choose a neutral grey in your scan.

Click on the lower of the 2 grey boxes and a Color Picker appears.

Choose absolute White (in the corner) and click O.K.

The color picker Box will disappear. Take the slider on the bottom ALL the WAY to the Right “Lightness +100″.

Now do it again, this time selecting a “Black” area. It will Not be full Black, so choose it again by clicking in a corner of the Color Picker.

Move the slider All the Way to the Left (Lightness -100).

You will need to do this “First lighten greys to White, then strengthen darks to “Full Black” at least one more time (difficult scans may require several more passes).

The scan above appears done after the 2nd “Whitening” stage, but if you click (with the “eyedropper”) on several “Black” locations, you find that Some of them were not quite “full” so repeat the darkening step as well.

There you have it! Converting “Raw” scans to pure “Black and White” made simple by converting to Greyscale, then back to RGB before using the “Replace Color Feature”.