Removing unwanted colors

[mdavis]

This may not be the right section in which to throw this out for discussion, but I thought it might merit some interest among some of you.  Although I am an avid amateur photographer and use Photoshop with Curvemeister on a regular basis, my regular job is related but quite different.  I work in a forensic laboratory as a chemist, crime scene investigator (yes, I was a "CSI" before it became a popular buzz-word) and latent print examiner.

Inherent in the photographic needs of forensic photography is, of course, the need for accurate color balance, but often in the realm of latent print work, it is a challenge to use Photoshop and curves to remove unwanted colors in order to enhance a fingerprint against a multi-colored or non-contrasting background.  This often involves the use of FFT filters, channel curves and other more esoteric programs and plug-ins to bring a nearly invisible latent print out of its background clutter to better view and analyze it.

I have just obtained a new program (perhaps this post should be moved to the software section?) that appears to be a modified "Color Range" plug-in for use in Photoshop.  Called a "Color Deconvolution" plug-in, it seeks to enhance things such as separation of similar colored writing inks.  By clicking on both the "wanted" color and the "unwanted" color(s) you can bring images into view that would be quite difficult under normal curve-channel circumstances.  There is a demo of this program available at the following web site.  I did send a donation for a licensed full working copy, but have not had time to really test it yet.  The free demo appears to be fully functional but limited to small file sizes.  (link below)

I had also thought about finding a good example photo or scan to upload to the Challenge section, although the desired results are perhaps a bit different than tweaking a photograph for display.  But then, maybe any exercise can be beneficial.  Here's the link to the program that claims to be a sophisticated algorithm in 3D colorspace (Mike, this is your field of expertise).  I wonder if similar results could be obtained in Photoshop without the plug-in.....

http://home.planet.nl/~ber03728/4N6site/improc/decoplugin/main.htm

If anyone might be interested in something like this, I'll see if I can find some demo images to work on.

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This is quite fascinating.  It may well be that the chosen color space is key to unraveling similar colors.