On 2015-04-17 7:36 , Eric Weir wrote:
I checked out depth of field apps in the Apple App Store. I found several, but
didn’t find Peter’s f/Calc. Ended up purchasing Simple DoF.
Using it I get different results from those you report above:
For 200mm, f/ll, at 20’ I get DOF of 1’4” versus you 4”.
For 50mm, f/11, at 20’ i get DOF of 31’3” versus your 5’9”.
For 200mm, f/22, at 20’ we are closer. I get 2’8” versus your 2’11"
I trust you more than the app at this point. But why the—for the most part—wild
discrepancies?
i know you've already purchased an app, but for the benefit of others there
are dozens of websites that do the same thing; here is just the first one i
found, probably doesn't look great on mobile:
<http://www.dofmaster.com/dofjs.html>
it has K-7 but not K-5, but it doesn't seem to change the circle of
confusion for different APS-C camera models (it seems to me circle of
confusion should change with sensor resolution)
for 200mm, f/22, 20 feet is shows 2.68 DoF, which is 2'8"
when in the field you may not have a data signal, so when i have time i'll
see if i can find one that can be stuffed into a JavaScript bookmark and
work without an internet connection; or you could just print this table to a
PDF and store it in Dropbox, or print it and put it in your wallet:
<http://www.dofmaster.com/doftable.html>
there are, of course, also old school "slide-rule" type DoF calculators that
don't require batteries
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