There is also the claim of 'fall off' by a professional photographer, Perry.
Surely you mean
Percy, the "professional photographer" who was too scared to come on the show to defend his claim.
As you know, NASA claims the only light source was the sun...
The only
direct light source is the sun. However, David Percy proved himself to be utterly incompetent when it came to
indirect light sources, texture hiding, and all the other important concepts that come into play when you actually practice photography.
but this 'fall off' indicates extra lighting by the way the background falls off...
You must be new to this.
The claim is that falloff is the product of using only
one light, which wouldn't be able to illuminate the entire ground surface. You would add extra lighting to
get rid of the falloff, what lighting designers call a "wash." But then you have multiple shadows.
If you had watched the video you posted, you would have seen the actual effect of using only one light to try to illuminate a large area.
when one would expect the ground to show uniform brightness.
Why would one expect that?
Originally, yes. But the Apollo photographs have been widely duplicated by both photographic and digital means. NASA made a set of dupe masters from the original transparencies and then keep the camera originals in a vault. NASA turned the dupe masters over to a commercial photo service, which handled photo requests for decades until some of the dupe masters (and in other cases, prints made from them) were scanned by whoever had them and put on the web. All the pictures you will ever see are scans of at least a second-generation dupe.
Because NASA has since brightened it and increased the dpi. (Ref. A11-69-HC-684). As you can see, it has had the effect of making Buzz now look washed out. The one above was the original used by the GUARDIAN (17.7.2019, Jonathan Jones), who likely got it from the Smithsonian or one of NASA's own webpages.
Or stated more obviously, the photo has been through a number of hands that have nothing to with NASA, has been altered for reasons that have nothing to do with scientific or historical accuracy (i.e., to make it look good for publication), and from which absolutely nothing can be inferred in a photometry sense. Just because you know its NASA Apollo photo reference number doesn't mean you have an original.