Mathew Collins Posted August 28, 2017 Share Posted August 28, 2017 Hi, I have seen the following calculation in a book. "For example, for a 50mm lens at f/8 with a circle of confusion of .0001", the hyperfocaldistance is 40 feet. Thus, if you set the focus distance at 40 feet,everything from 20 feet to infinity will be in focus." If i calculate using the formula H = F x F / (f x Cc) = 50mm x 50mm /(8 x 0.00254mm) =123031.5mm =403.64ft Anything wrong with my calculation? Link to comment Share on other sites More sharing options...
Premium Member Dom Jaeger Posted August 28, 2017 Premium Member Share Posted August 28, 2017 A more typical CoC figure would be 1/1000 of an inch: 0.001" or 0.0254mm. Looks like an extra zero slipped in after the decimal point. Link to comment Share on other sites More sharing options...
Gregg MacPherson Posted August 28, 2017 Share Posted August 28, 2017 Does anyone still use the old style Kelly wheel type DoF calculator? I mean the physical rotating disks that work like a slide rule. They're a great way to get a more global feeling for the variables, and so simple, reliable. Link to comment Share on other sites More sharing options...
Premium Member Simon Wyss Posted August 28, 2017 Premium Member Share Posted August 28, 2017 I just missed slide rules. At school we were the first class allowed to have an electronic calculator, that was in 1977, a TI-59. But I got well drilled in mental maths before gym. As a rule of thumb I reckon with a third of the real distance as HD. In general news gathering people and everybody on quick and dirty jobs set focus too far. TV is full of such hyperfocal shots. It should be hypofocal distance. Link to comment Share on other sites More sharing options...
Mathew Collins Posted August 29, 2017 Author Share Posted August 29, 2017 (edited) A more typical CoC figure would be 1/1000 of an inch: 0.001" or 0.0254mm. Looks like an extra zero slipped in after the decimal point. I quoted from 'Cinematography - Theory and Practice' by Blain Brown page 278. If CoC is 0.001, then the calculated hyperfocal distance would be 20 feet. Edited August 29, 2017 by Mathew Collins Link to comment Share on other sites More sharing options...
Robin R Probyn Posted August 29, 2017 Share Posted August 29, 2017 Does anyone still use the old style Kelly wheel type DoF calculator? I mean the physical rotating disks that work like a slide rule. They're a great way to get a more global feeling for the variables, and so simple, reliable. Those white plastic ones..? I had one when I was a focus puller.. short lived career .. even easy, arse holes to infinity shots I would whip out that calculator and make it look really difficult in front of the make up ladies I fancied .. never worked.. and usually shot out of focus too.. Link to comment Share on other sites More sharing options...
Premium Member Dom Jaeger Posted August 29, 2017 Premium Member Share Posted August 29, 2017 I quoted from 'Cinematography - Theory and Practice' by Blain Brown page 278. If CoC is 0.001, then the calculated hyperfocal distance would be 20 feet. Try it again, using 0.0254 (mm) as the CoC figure in that formula, instead of 0.00254. You'll get the same answer as before, only divided by a factor of ten, which is about 40ft. Link to comment Share on other sites More sharing options...
Mathew Collins Posted August 29, 2017 Author Share Posted August 29, 2017 Try it again, using 0.0254 (mm) as the CoC figure in that formula, instead of 0.00254. You'll get the same answer as before, only divided by a factor of ten, which is about 40ft. That was a mistake. Please read "I quoted from 'Cinematography - Theory and Practice' by Blain Brown page 278. If CoC is 0.001, then the calculated hyperfocal distance would be 20 feet." as I quoted from 'Cinematography - Theory and Practice' by Blain Brown page 278. If CoC is 0.001'', then the calculated hyperfocal distance would be 40 feet. Link to comment Share on other sites More sharing options...
Mathew Collins Posted August 31, 2017 Author Share Posted August 31, 2017 Thank you all. Link to comment Share on other sites More sharing options...
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