I was attempting to capture the full moon tonight using my Canon EOS R50 mounted on a tripod. I had a telephoto lens attached to the camera via a Canon adapter, as this lens was originally designed for my father’s Canon Digital Rebel and had an incompatible mount for the R50.

While zoomed in on the moon to fill the frame, I observed an unexpected behavior: the camera appeared to automatically zoom the image back out. I was under the impression that the camera itself lacked the capability to adjust the zoom setting, but the viewfinder clearly indicated a change in magnification

Update: In case it is important, the lens has image stabilization built in, but I have it turned off as it lets me set focus and recompose better.

  • Durandal@lemmy.today
    4·
    4 days ago

    Yup. Either this or didn’t notice that the lens zoom had loosened due to age and wear and it was slipping because it was being pointed up. Focus breathing would be a first guess though.

    • WasPentalive@lemmy.oneOPEnglish
      1·
      3 days ago

      I just tried this - Lens is off the camera (and has a lens cover for both ends) sitting looking straight up. I turn zoom ring until the lens is fully extended. I wait a bit then I check for zoom movement and found that the lens was still fully extended.

      I don’t know if this is a valid test because sitting on a table - the lens is not getting any electricity from the camera body.

      • Durandal@lemmy.today
        1·
        3 days ago

        Well the issue can be when it’s tilted up that if you let go of the zoom ring it’s heavy and might slide back from gravity. Laying flat it isn’t fighting gravity heh

        • WasPentalive@lemmy.oneOPEnglish
          1·
          2 days ago

          I had the lens pointed up. It was sitting on the camera-end cap. I was not holding the zoom ring for this test. It held the zoom for the test and remained fully extended.

    • WasPentalive@lemmy.oneOPEnglish
      1·
      3 days ago

      I can’t say for sure, but I think I had my hand on the zoom ring. The moon will still be full enough tonight perhaps I will try again. I looked up “Focus Breathing” and I am not sure what it is really talking about.

      • Durandal@lemmy.today
        1·
        3 days ago

        Essentially it’s a small to moderate shift in amount of zoom because of the movement of the internal elements during focusing. I would just look up focus breathing on YouTube and see some examples and if it matches what you noticed.