Olympus AF fine tune

[Paolo DePetrillo]

The AF Fine Tune value for Olympus can be extracted by adding this line to extract_af_tune() in src/gui/exiv2_property.cc:

        case OLYMPUS:
            return extract_property(QString("Exif.OlympusCs.AFFineTuneAdj")).section(" ", 0, 0);

The exif tag contains three values and this code extracts only the first one. Not sure if it works the same way for all cameras and lenses, but on my E-M1 II, the first value is the value in use for the current image based on the lens and zoom focal length. The second value is the "TELE" value set in the AF Fine Tune menu for the lens, and the third value is the "WIDE" value. It looks like the value is interpolated between the TELE and WIDE settings based on the focal length.

[Frans van den Bergh]

Thanks, this seems to work well!

I've committed these changes to the repo.

Regards,
Frans