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Lens Aperture is the simple answer. The darker picture was set at around f11, the lighter picture had the aperture wide at around f4. The lunar landscape is lighter as a result but at least it recorded Buzz Aldrin correctly. Spotlights are not even required.

The reason why the ground in shadow was dark while Aldrin was fairly light is because the white suit reflected around 72% of light while the ground around 8%.   

What is going on in these pictures from Apollo 11? In one shot the Lunar Module is in deep shadow and it can hardly be seen. The next shows it brightly lit. I know what it is... A spotlight! Aha got you all now. Yes it’s in a studio after all!

If a spotlight was used, where are the extra shadows? My own test shown above did not require a spotlight; just extra opening of the aperture and the background was not vastly overexposed either; just a little but still usable. 

Big Mystery - two shadows of different lengths.  It took 20 minutes to demonstrate it's perfectly normal. Try it yourself.