I took a number of these “screenshots” during that period in different theaters. The camera always registered a hot spot from the projector’s light source in the center of the frame. Everything was shot with Kodacolor 400 print film (who knows how the color temp lined up).
Looking at the prints themselves, it’s apparent that some general brightness compensation was applied during processing. If you like, I could repost these without cropping the black masking at the edge of the movie screen. I think you would find that if I equalized the level of the masking to be the same for all, the two shots of Artoo in the canyon would appear even darker that what I posted originally.