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Crop factor (again)

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    Crop factor (again)

    Robert quite rightly says that the crop factor does not change the focal length of a lens.
    Canon, however, are peddling the "1.6x more reach" in their latest R7 ads.
    One factor I think Robert should have mentioned is the pixel density. Given a good lens, then the 30MP R7 will out-resolve a 20MP R6. That means greater precision, and enlarging the cropped image will be sharper. That does lend some credance to the "more reach" argument. Greater resolution on the sensor would however be a more accurate description, as, once again, the lens hasn't changed. But a higher resolution sensor does offer greater resolution and enlargement capability than a lower resolution one.
    Then you are into the realms of diffraction limited aperture. The R7 is diffraction limited around f/6, so you still need wide aperture lenses to get the best out of it. The 100-500 is probably optimum, limiting around f/7.1 which just starts to enter the DLA of the R7.
    Then again, it depends. A larger pixel has lower noise, generally speaking, so the R6 would out-perform the R7 in lower light. In fact, the R7 is less capable than the 7DII in that respect. Seems to me to be a 90D upgrade, not a 7DIII mirrorless.

    I agree the manufacturers should be more careful in their use of terminology.....the concept of reach is not a good term either when you think about it, whether the image on the sensor is due to the optical angle of view with a long lens or a 'crop' having used a smaller sensor....its the same end result - a smaller selected area of the image before you.....nothing has been reached.

    Apple advertise optical zoom on the Iphone actually has three separate fixed focal length lenses, and between those focal lengths the electronics will compose an image based on the supposed zoom that you have set....its three fixed lenses and box of electronics - no optical zoom at all.

    Makes me mad....
    Brian Vickers LRPS


      I was pleased to see neonlamp mention diffraction. I had to explain this to a student earlier this week who had ventured beyond the acceptable aperture for an R10 in an attempt to get greater depth of field and had produced images that were plagued by the effects of diffraction.

      No longer using Canon but still teaching new Canon users (and others) the gentle art of Photography.