Winsor wrote:
>>it is sort of like holding your hand
above a flame. Your hand can absorb a lot of energy over a long time
without burning it. You can even plunge your hand into the intensity of the
flame for an instant without burning it, but if you put your hand close to
the flame for a short while you will get a very good exposure. :-)<<
Nice comparison Winsor, I've find in Michael Langsford excellent "Advanced
Photography" (Focal Press) a very extensive explanation of reciprocity
failure with another comparison:
"Reciprocity law failure can perhaps be likened to filling a narrow necked
bottle with water, in a very dry climate. If the volume of water is applied
all at once, as from a bucket, much will fail even to enter the bottle. If
on the other hand it is fed in drip by drip very slowly, a high proportion
of water will be lost by evaporation. The optimum filling rate is the one by
which all the water enters the bottle, but in a period short enough to
minimize evaporation."
Except this "watered" explanation the technical side is well detailed .
regards
marc
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