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Thoughts on PDAF cameras and non-SEL lenses

Discussion in 'Sony Alpha E-Mount Cameras' started by dbmiller, Apr 29, 2014.

  1. dbmiller

    dbmiller TalkEmount Top Veteran

    777
    Mar 2, 2012
    New England
    Now that my SEL lenses are all at the latest firmware, and I have the right settings for the various AF modes, I got to thinking about what Sony could do for non-Sony lenses to help focus.

    Now, my understanding of the way PDAF works is that the sensor can not only detect that the image is in focus or not, but also which direction the lens needs to go, and how far to move it. I'm not sure why it can't be used on non-Sony lenses like the Sigma 19/30/60 other than maybe that last part - How far to move the lens. That could also be why the firmware in the SEL lens needed to be updated.

    So if my assumption is correct, then even with a non-SEL lens, the camera should still know if the image is in focus or not for a particular PDAF point. So why not use that information to display focus feedback? So instead of using focus peaking and contrast analysis, just display the rectangles where the PDAF says that zone is in focus?

    This would work for the Sigma's, but would also work for legacy lenses as well. As you focus the lens, the little rectangles will show up or disappear as the focus distance changes. There should also be a way for the sensor to provide feedback as to which direction or how far to turn the lens, but I'm not sure how that would work. (Fuji X MF assist?)

    So to recap, my suggestion to Sony would be to add a new MF-assist option: PDAF tracking. When there's enough light for PDAF to work, use it. Otherwise use focus peaking.

    Now if I'm wrong about PDAF, then I just wasted my time writing this. And your time reading it. My apologies if that is the case. But this HAS to be possible. Look at what Fuji did with the split image MF assist.
     
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  2. dbmiller

    dbmiller TalkEmount Top Veteran

    777
    Mar 2, 2012
    New England