Paris

by Jon

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This is what I get pretty much every time when shooting in Live View mode using the Canon 50 1.8:

Live View shot

This is what I get when I'm lucky when focusing through the viewfinder:

enter image description here

This is what I get when I'm not lucky (20-30% of the time):

enter image description here

What's moderately interesting (and kind of confirms this blog post from LensRentals) is that the kit 18-135 STM has a much higher success rate when focusing using the viewfinder.

Is there anything I can do to improve focus accuracy with the nifty fifty except shooting in Live View mode? I imagine other lenses like Tamron 17-50 2.8 will have similar issues?

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I assume that you are receiving a "focus confirmation" signal in each case, and that these images are the result after you receive it. ? –  Russell McMahon Aug 10 '12 at 21:40
    
yes. they were all taken using a tripod, with a remote release cable and with mirror lock-up. –  Baczek Aug 10 '12 at 21:43
3  
Well, for one, the 50/1.8 does not have a USM AF motor, so its accuracy is wanting to start with. Combine the very low-grade AF motor in the 50/1.8 with an extremely thin DOF and what appears to be relatively low light and the lower precision of the dedicated phase-detection AF sensor, and your going to have a miss rate quite a bit larger than zero. The benefit of using live view here is that phase-detection is used to "get close", and contrast-detection is used to "finalize". Its actually the CD-AF in live view that is giving you the superb results...not the FPPD-AF. –  jrista Aug 11 '12 at 0:20
    
@jrista: Yeah, it wasn't sunlight, but it wasn't dark either. If I understand correctly, I need new lenses if I want to use a body with PDAF, or I can pretend I have a mirrorless and shoot with Live View. Correct? –  Baczek Aug 11 '12 at 7:00

1 Answer 1

up vote 3 down vote accepted

You don't have a body with AFMA (auto-focus micro-adjust), but there's the possibility of sending body and lens to Canon for calibration, that should get the phase-detect AF to work as good as it can with that lens.

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Didn't try it but I'm going to accept anyway. Sounds sensible. When I get around to actually doing it, I'll try to remember to update this question. –  Baczek Sep 24 '12 at 12:43

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