My current method to determine AF-Fine Adjust values

Started Mar 26, 2013 | Discussions thread
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Re: My current method to determine AF-Fine Adjust values
In reply to Kerusker, Jun 27, 2013

A more accurate method for people who do already own FoCal for their Canon or Nikon ...

1. Have the Pentax on a tripod take JPG shots of some test chart using normal PDAF autofocus. But use AF fine tune values of e.g., -20, -12, -4, 4, 12, 20 respectively (6 or 12 shots if doing 1 or 2 shots for each). Move focus manually, e.g. to infinity, in between.

2. Write the AFMA (AF manual adjust aka fine tune) values into the images EXIF header, using exiftool. I am sorry but I don't remember ATM the exact name of the exif field which are to be written. It may be necessary to fake more fields to make FoCal detect a Nikon or Canon.

3. Read the test shots into FoCal's manual mode. You need to connect your other camera to validate the license in order to enter manual mode. FoCal will automatically determine and display the optimum AF fine tune value. More on manual mode:

The optimum fine tune values depend on many variables, like focus distance, color temperature, zoom focal length, which AF point to be used etc. This more accurate method gives a better feeling about the variances and let's you choose a compromise. A more heuristic try-and-error method may lead to a setting which works worse in the field.

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