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Exposure Latitude Can Explain This

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Posted by Forum Master on July 24, 2001 17:41:37 UTC

Not much has changed with film basics including the dynamic range that film can capture.

Ask any professional photographer about exposure range and they will tell you about their many methods of manupulating this to expand or contract the dynamic range to accomodate the subject of their photography.

The photographs we see of the astronauts on the Moon were taken in very bright sunlight. The stars are relatively dim campared to all the subjects illuminated by the Sun, including the astronauts, their equipment and the Moon's surface.

To capture the images of the stars, the photographers would have to severly overexpose the things illuminated by the Sun rendering them as just white with no detail. To capture the image of the astronauts, the exposure would have to be adjusted to restrict the amount of light reaching the film so the film could register properly. The star light would also be reduced by this restriction and would probably be so dim as to never register on the film. Perhaps a modern analysis of the original negatives might reveal some evidence of the star's images, but not enough to ever be visible to the naked eye.

If you were to put a professional photographer on the moon with his best view camera and associated meters, guides, calculators, etc. he/she maybe, just maybe, might be able to create an image that would capture the very bright detail of the astronauts and the very dim points of light with one exposure onto a special negative with very broad dynamic range characteristics developed in such a way as to futher broaded the range and printed in such a way to broaden it further still.

Or you could put an astronaut on the moon with a Hassablad with typical black & white film who is busy collecting rocks, inspecting the moon, studying things, worrying about staying alive, etc. I don't think the astronaut cared at all about imaging stars when his task was to take photographs of lunar details bathed in bright sunlight.

So this is one reason why stars are not obvious on lunar photographs.

John

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