|Posted on Monday, December 23, 2002 - 10:15 am: ||
You may want to examine the surface under a variety of excitation wavelengths in an attempt to luminesce the adhesive (you didn't mention using any luminescent developing powder). In some instances, the powder may quench luminescence of the adhesive similar to the mannner in which ninhydrin developed impressions quench the glowing background of cardboard to render dark identifiable ridge detail when that ridge detail is too faint for identification with normal room (white) light viewing. Another advantage of using luminescence is that it will often eliminate interference present with crinkled aluminum foil in white light. Perhaps it will reduce or eliminate the photography problems you are experiencing with your thin, mangled metal.
In that you apparently can see the ridge detail by holding the metal surface at various angles relative to your light source, you may want to make multiple exposures at various lighting angles and then create a mosaic of the impression... sort of a cut and paste jig-saw puzzle. If you do not move the camera, and enter various lighting-angle exposures into individual layers of a Photoshop image, you can then selectively delete layers of the areas without ridge detail in an attempt to build an identifiable impression. You would not be "creating" ridge detail, and by preserving a copy of the original image your step by step work can be examined by defense experts with a need to prove that you did not manufacture non-existent ridge detail through selective electronic "dodging." The LP examiner "building" the layered impression also should not previously have seen the suspect's record impression(s) for the case in question, lest there be a claim that he/she chose only those fragments of ridge detail which helped build an incriminating impression.
If necessary, you can instead (or also) vary the camera position to optimize ridge detail captured in different areas on the evidentiary surface, but registration (alignment to coincide with each other) of the images may be much more difficult.
|Posted on Monday, December 23, 2002 - 07:42 am: ||
I have a piece of thin metal that has adhesive on one side. There are very good impressions in the adhesive, however due to the mangled condition of the metal I am unable to photograph them or place them in the AFIS scanner. I did try sticky side powder on a small area of the metal and it did not work well. Regular black powder will not work due to the adhesive. I am looking for any ideas on how to enhance, preserve and/or photograph them.