I entered my Canon 100-400 zoom as a specific lens. There seems to be some bugs in the calculation algorithms. If I set the FL to 400, F8 and subject distance to 100', the near far calc gives 60', 3.4 total, and 63.4 feet. How can that be?! This error shift is not affected by aperature. The specific values change, of course, but the near and far is way below the subject distance regardless.
I have also found that with other lenses, while the DoF at least includes the subject distance, the calculated DoF is much more liberal than the iPhone app "Bokeh", which I have used for some time and consider fairly reliable. I imagine that the differences are based on the definition of CoC and I will will look into the custom settings to see if I can get more conservative calcs, but something is definitely wrong in the 100-400 preset calcs.
This app has some nice features missing form Bokeh, but it is meaningless if I can't trust the results.
Thanks.
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Upon further trial I found that the critical focal length at which the DoF starts to fall below the subject distance is a function of both FL and subject distance. For example at F8 and 50' SD the DoF meets the SD at 145mm. Anything greater and the DoF fall below the SD. Change the SD and the FL that meets the upper end of the DoF changes as well. This after I deleted all my lenses and created a hypothetical lens of 16-400.
Something is CLEARLY wrong.
At FL of 50 mm & F8 I could get good agreement with Bokeh by changing the CoC to .020.
Would sure like to know when this app gets fixed as I would prefer it over Bokeh simply because it "remembers" the last screen used and stays in the units preferred (feet), but until it is fixed it's a non starter.
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Thanks for the feedback. I'm away from my development computer for a few days over the holidays. I will look in to your problem in detail when I'm able to in a couple of days.
Brad
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I entered my Canon 100-400 zoom as a specific lens. There seems to be some bugs in the calculation algorithms. If I set the FL to 400, F8 and subject distance to 100', the near far calc gives 60', 3.4 total, and 63.4 feet. How can that be?! This error shift is not affected by aperature. The specific values change, of course, but the near and far is way below the subject distance regardless.
I have also found that with other lenses, while the DoF at least includes the subject distance, the calculated DoF is much more liberal than the iPhone app "Bokeh", which I have used for some time and consider fairly reliable. I imagine that the differences are based on the definition of CoC and I will will look into the custom settings to see if I can get more conservative calcs, but something is definitely wrong in the 100-400 preset calcs.
This app has some nice features missing form Bokeh, but it is meaningless if I can't trust the results.
Thanks.
Upon further trial I found that the critical focal length at which the DoF starts to fall below the subject distance is a function of both FL and subject distance. For example at F8 and 50' SD the DoF meets the SD at 145mm. Anything greater and the DoF fall below the SD. Change the SD and the FL that meets the upper end of the DoF changes as well. This after I deleted all my lenses and created a hypothetical lens of 16-400.
Something is CLEARLY wrong.
At FL of 50 mm & F8 I could get good agreement with Bokeh by changing the CoC to .020.
Would sure like to know when this app gets fixed as I would prefer it over Bokeh simply because it "remembers" the last screen used and stays in the units preferred (feet), but until it is fixed it's a non starter.
Paul,
Thanks for the feedback. I'm away from my development computer for a few days over the holidays. I will look in to your problem in detail when I'm able to in a couple of days.
Brad
Paul,
I found the source of the problem. There was an error calculating the depth of field for long subject distances.
I've uploaded a new version to Apple. Watch for Version 2.0.1 in the App Store in a few days.
Thanks again for pointing this out.
Brad