App for f-stop time calculations (iOS)

RalphLambrecht

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markbau

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RalphLambrecht said:
good idea but why not just read it off table?
Click to expand...
Ralph, I'm curious as to why your base exposure times are such odd numbers. I've been using the Nocon numbers for many years in which the progression is simply, 2.5, 5, 10, 20 40 seconds with his numbers in between, (see attached pic)
 
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radiant

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Ralph's table is a real f-stop table with all step times in accurate form.

markbau your table seems to be roughly rounded numbers when base f-stop of 1.4 and then increased with 1 stop (in f-stop system the times are 2.6s, 5.3s, 10.6s, 21.1s).
 

markbau

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vedostuu said:
Ralph's table is a real f-stop table with all step times in accurate form.

markbau your table seems to be roughly rounded numbers when base f-stop of 1.4 and then increased with 1 stop (in f-stop system the times are 2.6s, 5.3s, 10.6s, 21.1s).
Click to expand...
I don't know about "roughly rounded numbers" If you agree that 10 sec is a one stop increase from 5 seconds, and 20 seconds is a one stop increase from 10 seconds I don't see the need to have base exposures that are not whole numbers. A half stop increase from 10 seconds is 14.1, a full stop is 20 seconds. BTW, Rudmans f stop calculation table is identical to Nocon's. 5, 10, 20 seconds are full stops. I still don't understand why base exposures need to be anything but whole numbers. Rudman's base exposures are all whole numbers. What am I missing here?
 

RalphLambrecht

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the numbers in my table follow a geometric scale based on 8 or 16 seconds. They are no more 'odd' than the aperture or timing labels on your cameras or lenses.
 
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radiant

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The "secret" formula is just a power of 2 to f-stop -> in math 2(f-stop).

If you need to calculate time to f-stops, just calculate log2 value of your time and you get f-stops.
 
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radiant

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It is an app to help you with f-stop time calculations. It "converts" f-stops into seconds and you can see the added f-stops in terms of time sum and the incremental amount between stops.

F-stop calculation is mostly used in darkroom printing.
 
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