12-12-2018, 07:28 PM
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 after the first photograph
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. The background can often interfere with visualising the print, especially with fingerprints and so the removal of the background can reveal fine details in ridges, valleys and pores etc.
I have experience using the subtraction method in Photoshop but as this is a university course I 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 between photographs there sometimes can be very slight movement.
Thanks for your help/advice, David
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 after the first photograph
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. The background can often interfere with visualising the print, especially with fingerprints and so the removal of the background can reveal fine details in ridges, valleys and pores etc.
I have experience using the subtraction method in Photoshop but as this is a university course I 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 between photographs there sometimes can be very slight movement.
Thanks for your help/advice, David