Thanks for posting those comparison photos, it seems to me that some of those shirt photos have been artificially enhanced, who would do such a thing and what would they have to gain??
JohnM
In the JFK case, I would say most CTs are into such manipulation, either producing or feeding on it.
But sometimes a bad image on the Internet is a combination of things from the past, such as: early-generation home scanners, cheap software, badly-calibrated gamma on computer monitors, the color table limitations of GIFs (when people wanted small file sizes because of low internet speeds) and so forth that made scans done in the 80s and 90s go all wacky.
Today there's higher-quality digital devices, easier monitor calibration, the PNG format and industry standards that maintain at least some degree of quality and consistency.