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[filmscanners] Re: Real-World Scene Brightness Range



David writes:

> I've not measured this but bright sun on
> a white shirt must be pretty close to 10
> stops from dark cloth in heavy shade.

I'm not so sure.  There's often more light falling on dark objects in the
shade than one might think--but the brightness of nearby direct sun on
light-colored objects can create the impression that the difference is
really big.

Note that when you pass from bright sunlight to deep shade, your eyes adjust
instantly--no accommodation required.  This implies that there are only a
few stops of difference between the two (the aperture range of the human
iris is only a few stops).

On the Moon, the situation would be different.  With no atmosphere to
reflect light into shadows or attenuate direct sunlight, you might easily
get ten stops between sunlit zones and shade.  It must have been quite a
problem for astronauts.


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