The HSCA Photographic Panel studied CE-133A, CE-133B, the negative of CE-133B and Oswald's camera (among many other items related to the photos, such as first generation prints of CE-133C).
The panel first performed a visual inspection of the photos, by use magnifiers and microscopes. During this inspection, the panel made enlargements of the photos using various exposures and ranges of contrast. These enlargements produced prints which ranged from very light to very dark. In the darkest parts of the photos, the detail could be seen best in the lighter prints. In the lightest parts of the photos, the detail could be seen best in the darker prints. The panel felt this was the best opportunity of detecting any evidence of falsification anywhere in the pictures.
The panel also used digital image processing to determine if there were any unnatural edge lines or differences in grain structure or contrast.
Both photos (CE-133a and CE-133B) were also studied by the panel using stereoscopic techniques, which allowed the panel to see the photos in 3-D. This method will detect forgeries in prints because it produces a photographic copy of a photograph.
When viewed in stereo, these copies will not project a three-dimensional image unless made from different viewpoints along the same axis. Retouching of the original photo can be detected when two photos depicting the same scene are viewed in stereo, the retouched print will not be on the same plane in which it should be lying; the items seen in the photo will be either in front of the plane or behind the plane. Because of this, when viewed stereoscopically, fakery can easily be detected.
One final method the panel used to examine the photos was photogrammetrically.
Using all of these methods, the HSCA Photographic Panel detected no signs of forgery.
I have a question about stereoscopic viewing. If you photograph the same objects from slightly different directions they will appear in a 3D fashion when viewed through a stereoscopic viewer. I could see how that works for the background because it's in the exact same position from two slightly different viewpoints. What I don't get is how that could apply to Oswald himself because he is in different positions for each photograph. I thought they were only verifying the backgrounds of the backyard photographs?
