Re: ATM All Sky Instrument - a comment on reciprocity failure

[Brian Nestel <blast@aloha.net>]

Hi:
Reciprocity failure as Richard stated is simply the failure to record
low light levels not a loss of sensitivity. for instance for a certain 
reciprocity index figure it may take a certain number of photons per 
time period(extremely short) to keep the film crystals activated
if the level is below this the film crystals reset and you loose the
object. Film does not loose sensitivity during long exposures. 
Long exposures sometimes appear to loose sensitivity due to incident
light(sky fog) fogging the film and loosing low level definition, just
shortening the exposure by as little as five minutes sometimes will 
retain the low level. 
The new kodak pro color films have a reciprocity index that is close to
that of hypered color film so its not worth the effort of hypering for
the average person.
-- 
Aloha   159 36 W, 21 58 45 N
Brian   Middle of the Pacific,
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