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Modern slide film speed evaluation methodology
Hello,
I've beeen searching quite a long time for the answer. In ISO/DIS 2240 there's is a color reversal speed defined as square rot between Dfog+0,2 and tangent to shoulder or 2,0D exposure. Only the 2,0D point gives right speed for low and high sensitivity slides. Everything is good with this bonduary condition and with film speed equation: ISO speed = 10/10^(logEs+LogEt/2) Es - shoulder point (depends on norm) Et - toe point (0.2+Dfog) But this is only a synthetic speed based on HD curve. If you now take a photograph of gray card then its density on film is somehow 1.25-1.4 - exactly how the repriocity of slide should be. From speed equation density is lower - below 1,0D! So can somone clairify this issue? __________________________________________________ ____________________ Jack Zagaja - photographer, designer, programmer free photoshop plugins, photographic assistance opinions and much more ... |
#2
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Modern slide film speed evaluation methodology
Jacek Zagaja wrote in message . ..
Hello, I've beeen searching quite a long time for the answer. In ISO/DIS 2240 there's is a color reversal speed defined as square rot between Dfog+0,2 and tangent to shoulder or 2,0D exposure. Only the 2,0D point gives right speed for low and high sensitivity slides. Everything is good with this bonduary condition and with film speed equation: ISO speed = 10/10^(logEs+LogEt/2) Es - shoulder point (depends on norm) Et - toe point (0.2+Dfog) But this is only a synthetic speed based on HD curve. If you now take a photograph of gray card then its density on film is somehow 1.25-1.4 - exactly how the repriocity of slide should be. From speed equation density is lower - below 1,0D! So can somone clairify this issue? __________________________________________________ ____________________ Jack Zagaja - photographer, designer, programmer free photoshop plugins, photographic assistance opinions and much more ... The freebblefratz is all wrong. The nasal passages are beyond the effluvium of the nexus. |
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