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Subtraction Technique - Forensic Imaging

Dec 12, 2018, 18:25 (This post was last modified: Dec 12, 2018 18:28 by dwarrington.)
Post: #1
Subtraction Technique - Forensic Imaging
Hello, I work in forensic science and am teaching a lab at a university using the subtraction method for footwear and fingerprints.

Effectively I have 2 photographs taken using a tripod and the same lighting and camera settings (I have JPEG and NEF files for both photographs)
- 1 is of a dusty partial footwear mark on a wooden floor
- 1 is of the wooden floor but with the footwear mark completely cleaned away

I want to subtract the background (cleaned substrate) from the photograph showing the footwear mark, leaving only the footwear mark which will hopefully reveal more detail that was visibly lost in the wood grain background.

I have experience using the subtraction method in Photoshop but as this is a university course am unable to get multiple licences due to funding etc and so I have started playing around with GIMP instead.

I have tried a few methods I found online loading the images as layers and playing around with the subtraction and difference modes with some success but was wondering if there were any other settings/changes I could use to improve this?

Also, is there an auto-align function in GIMP? e.g. solid lines between floorboards are aligned, not just the photographs themselves. As much as I try not to knock the tripod while cleaning the floor or taking photographs there sometimes can be very slight movement.

Thanks for your help/advice, David
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Dec 13, 2018, 09:03
Post: #2
RE: Subtraction Technique - Forensic Imaging
As it says in the forum announcements, this forum is had been DEAD for a long time.

The spammers keep trying to take over.

Save yourself from them and go to https://www.gimp-forum.net instead, which I see you've already done: https://www.gimp-forum.net/Thread-Subtra...ic-Imaging
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