Hi PPK,
Sorry I can't post often or at length - I've got a 2-year old who has earned the nickname "A-Bomb". He keeps me busy.
Re: Retouching, I'm sure you realize that virtually every photo you have ever seen in a magazine or newspaper or textbook has been altered somehow.
Usually it has been cropped to center and/or isolate the desired subject of the image.
Among the Apollo pictures, the most famous is, of course, AS11-40-5903.
here it is on the Wikipedia page (and, in case you were wondering, I have
seen identical version in official NASA publications and websites). When you compare it to a
less-adjusted version, you can see why it needed work: the image is
tilted and so badly framed that it cut-off the top of Aldrin's PLSS, including the antenna. We almost lost the top of the helmet, which would have
ruined the shot, from a standpoint of aesthetic appeal. Notice that in addition to rotating the image and centering on Aldrin, the Wiki photo has
also added black "sky" to the top of the image to aesthetically improve the centering, and also airbrushed-out the reseau crosshairs.
Does this mean that AS11-40-5903 is "fake"? Of course not. It is an authentic document of an historical event. It has simply been altered to
remove distracting imperfections. Come to think of it, I'll bet this image has had less work done than your average Playboy centerfold.
Since you ask about the sky, it's pretty easy to see that a uniform black is going to show any and every bit of dust or lint on the scanner when
converted to digital form. I have seen Apollo scans that do show specks, and I always find myself thinking, "Whoa, dirty scanner. Why didn't they
get rid of that? Lazy archivist..."
I do know of one
archive that has uncorrected scans. Because it hasn't had the contrast & color
adjusted, they look kind of washed-out, and any scanning imperfections are still there. The good news is that you can request downloads of the
highest-resolution scans available of NASA images.
Gotta chase A-Bomb. Later!