Parfocality through firmware

Started May 18, 2015 | Discussions thread
OpticsEngineer Veteran Member • Posts: 6,527
Re: Parfocality through firmware
1

I just tried that with my Nikon D7100 plus Nikon 18-140 zoom lens. The lens is most definitely not parfocal and I could not find a focus mode that seemed to try to do what you suggested. (first I focus on something, then I change the zoom and hope focus does not change... it changed a lot with the 18-140... it takes a shutter half press to refocus) I am not running the very latest firmware however.

I just tried this with my Sony RX10 too (not a DSLR) That camera is targeted for photo-journalists (according to Sony) so the behavior you described would be useful for that group of users. Focus did seem to stay pretty constant with zoom, and then when I stopped zooming,  active AF would be hunting in low light.   I did not try to figure out exactly what was going on.  But it did seem like the RX10 was smart enough to make a guess at where to be starting with the AF once I stopped pressing the electronic zoom lever.    The AF hunting only began once I stopped pressing the zoom lever.

Sounds like you are interested in AF systems. There is a handful of people here on dpreview that seem quite knowledgeable about those things. I don't know if they visit this forum though. I see the most informed discussions on the Nikon and Canon forums.

Here is an example article from a Canon regular.

http://www.dpreview.com/articles/5402438893/busted-the-myth-of-open-loop-phase-detection-autofocus

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