Here are the formulae for the free Windows DOF calculator from Digital
Light & Color <http://www.dl-c.com/Temp/> as taken from the help file.
Perhaps you can implement your own for the Mac
Chuck Norcutt
And here's a test case to check your work and keep units of measure
straight:
50mm lens @ f/8, resolution = 30 lines/mm, focus at 30.92 feet (the
hyperfocal distance), near focus 15.46 feet, far focus infinity (or
suitably big number) and hyperfocal distance 30.92 feet as previously
stated. With converted units: focus at 9.42 meters, near focus 4.71
meters, far focus at metric infinity ;-), and hyperfocal distance 9.43
meters (indicating some small rounding errors in the calculator)
Note that 30 lines/mm is quoted as the standard for a reasonably sharp
8x10 from 35mm film (3-4 lines/mm on the print). Resolution requirement
for the E-1 would be 60 lines/mm due to having to enlarge twice as much.
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Technical Notes:
This program computes depth of field according to the following formulas:
A = circle of confusion = 1/resolution
D = distance at which lens is focused
F = lens focal length
N = f stop
G = N*A
H = (F*F)/G
near focus = (D*H)/(H+D-F)
far focus = (D*H)/(H+F-D)
hyperfocal distance = H + F
Acknowledgements:
Depth of field formulas follow those derived by Nick Sushkin as modified
by Harold M. Merklinger, author of The Ins and Outs of Focus, available
from the author at:
Harold M. Merklinger
P.O. Box 494
Dartmouth NS
Canada B2Y 3Y8
http://fox.nstn.ca/~hmmerk
Bernard Frangoulis wrote:
> Thanks Piers, but unfortunately this is for PC only...
>
> Bernard (on Mac !)
>
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