[Alt-photo] f stop and log values

Loris Medici mail at loris.medici.name
Fri May 26 19:12:07 UTC 2017


Let me do it for you Keith;

1) Increasing the exposure means multiplication with the factor,
2) Decreasing the exposure means division by the factor,
3) For 1 stop the factor is 2^1 (^ being the exponentiation operator)
4) For 1/2 stop the factor is 2^(1/2)
5) For 1/3 stop the factor is 2^(1/3)
6) For n stop the factor is 2^n

Regards,
Loris.


On May 26, 2017 9:44 PM, "Keith Schreiber via Alt-photo-process-list" <
alt-photo-process-list at lists.altphotolist.org> wrote:

Bob -

To reduce exposure by 1/3 stop, multiply by 0.79.

If you are interested in how this this figure is derived I'll explain it
late. Gotta run now.

Cheers,
Keith

Keith Schreiber
jkschreiber.com




> On May 26, 2017, at 12:05 PM, Bob Cornelis via Alt-photo-process-list <
alt-photo-process-list at lists.altphotolist.org> wrote:
>
> I have a 31 step stouffer step wedge and need to know what fraction to
> increase/decrease exposure time when steps need to merge or separate.
>
> I know each step is 1/3 of a stop but wasn't able to find the
corresponding
> fraction to adjust exposure. The Stouffer website has this info in the FAQ
> section for the 21 step wedge only.
>
> My math is not good enough to wade through all the equations on Wikipedia
> to get the answer!
>
> Thanks
> Bob
>
> --
>
> http://www.bobcornelis.com
> _______________________________________________
> Alt-photo-process-list | altphotolist.org

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