The Image Doctors #211

Checking your lenses for defects

While most camera lenses produced these days are excellent, sometimes you get a defective one. It’s happened to both of us a few times over the years. This week, we’ll talk about what to look for when you’re evaluating a new lens, and how to spot common defects.

One thought on “The Image Doctors #211”

  1. About the Fuji AF issues mentioned in this podcast #211:

    I had Fuji X-E2, X-T1, X-T2, X-T3, X-T4, X-H1, X-PRO2 and X-PRO3 and always had autofocus issues with these cameras! Standing me in the same place photographing a static object and taking several distance measures with camera’s autofocus (AF-S, smallest point, no pre-AF, I had set my camera’s Shutter Release/Focus Priority to Focus priority for BOTH AF-S and AF-C), I have different distances measured. Sometimes when taking a photo of a landscape or of a far building, in one measure the camera says that it is 3 meters far and next time it says it is in the infinite.

    Analysing these cameras’ AF behaver and because the camera measures the distance with the diaphragm closed to the selected f-stop, AF processor does not know the difference between what is in focus and what seems to be in focus because of depth of field. These errors are more frequent with wide angle lenses and closed diaphragms (great depth of field) than with tele lenses and open diaphragms, like the 56mm f/1.2 or the 90mm f/2 (narrow or inexistent depth of field). With the latter the photos are practically 100 per cent sharp focused.
    In the meantime, I managed to find a way to minimise this focusing problem and ended up buying an X-T5.

    You can get more accurate autofocus by
    – switching the focus dial to manual focus,
    – setting the AF+MF input in the focus menu to ON,
    – changing the INSTANT AF SETTING input to AF-S or AF-C
    – and using the AF-On button to focus.

    Why? When using AF-S or AF-C, the camera focuses with the diaphragm closed to the selected aperture, but with this setting and manual focus and the AF-On button, the camera focuses with the lens fully open, which minimises depth of field resulting in more accurate focusing, and only closes the diaphragm at the moment of shooting.

    I don’t understand why with this method the camera focuses with the diaphragm all the way open and in AF-S and AF-C modes it focuses with the diaphragm closed!!!

    I think Fuji could add to the menu the possibility of choosing whether to focus with the diaphragm closed for the selected value or with the diaphragm wide open, regardless of the pre-selected value, in order to minimise depth of field and obtain a more accurate focus. Or not?

    I know several photographers who bought Fuji cameras and ended up giving up, selling their Fuji equipment and opting for competing brands because they don’t have this autofocus problem.

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