I've been using the Focus Bracketing feature on my 90D, which gives me choices in terms of the number of shots and the Focus Increment. These will vary with lens, aperture, size of and distance from the subject, but I was wondering if anyone had come across a formula for working this out in advance of pressing the shutter. At present I do it entirely by guesswork.
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If you have one there are smartphone apps that will calculate DoF for you once you’ve entered all the required parameters, divide the DoF into the total depth you need to cover and you should get an indication of how many steps you need; you’ll need to add in a small percentage for contingency. I’ve never tried this as my cameras do not have this facility but I would think it should work. I do my focus stacking manually and refocus using the magnifier for each step.
Ian
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Originally posted by Farider View PostIf you have one there are smartphone apps that will calculate DoF for you once you’ve entered all the required parameters, divide the DoF into the total depth you need to cover and you should get an indication of how many steps you need; you’ll need to add in a small percentage for contingency. I’ve never tried this as my cameras do not have this facility but I would think it should work. I do my focus stacking manually and refocus using the magnifier for each step.
IanUsing Tapatalk
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I thought I'd try a little experiment so I took some photos of a steel rule so I could measure the change in distance of each shot with different increments. The table below shows some of the results. The 2nd and 3rd columns are showing the change in 32nds of an inch, so a bit less than a mm. But what this does show is that Canon's Focus Increments are on an ordinal scale, not an interval scale, the higher up you go, the greater the difference. If I did enough measurements I would end up with a graph that showed a curve getting increasingly steeper.EOS 90D with EF-S 35mm. Initial point of focus approximately 5 inches from the front of the lens.Focus Increment f/2.8 f 8.0 1 1 3 4 2 5 10 10 21 Last edited by BobSapey; 10-11-2020, 11:40.Using Tapatalk
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