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I've Canon 600D and I use the back button to focus and the shutter to meter, I've been using spot metering for over 2 years for now and I understand what's the difference between it and evaluative, I used to use evaluative before that.

I recently got Sigma 14mm f2.8 lens, it's discontinued now but I read good reviews about it, however the copy that I got seems to have focusing problems.

I shot 4 test shots for each metering mode on a tripod in this order: eval, spot, partial, centered

eval

spot

partial

centered

I was on Aperture priority mode all the time. All shots are at 2.8. As you can see the center weighted mode is the sharpest one, my camera doesn't behave like this with other lenses and this lens has focus problem because when I focus and use the back LCD to manually override the focus the image comes sharper.

Now the question is how by changing the metering mode on the camera the focus (the photo sharpness) change?

  • Those images are awful grainy. I suspect the variations have more to do with your camera's ability to focus in low light than anything else. Your 1 in 4 lucky shot just happened to be when using center-weighted metering. – Michael C Sep 25 '14 at 8:58
  • @michael they are just cropped tight. the iso was 100 in all shots – K'' Sep 25 '14 at 13:52
  • Setting ISO at 100 doesn't mean they weren't shot in low light. If you shoot at ISO 100 in dark enough conditions and underexpose by 3 or four stops you will get more noise than shooting at ISO 800 or ISO 1600. See photo.stackexchange.com/a/12489/15871 – Michael C Sep 26 '14 at 7:09
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    i suggest a control experiment: make four consecutive shots with the same metering and compare focus. related: are your results repeatable? – ths Sep 26 '14 at 14:20
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    sorry for being late on this one, but yes it's true that center-weight was the most lucky one in this case, I tried again later and it's the same issue regardless of the mode. I tried manual exposure and the same result, all were fine with manual focus set by me. So I guess you guys are right it was auto focusing problem after all. I returned the lens for a full refund and I got the Rokinon. – K'' Mar 6 '15 at 22:06
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It shouldn't, PDAF occurs before any metering adjustments are made because the quality of focus is directly dependent on the available light. Focusing should occur with the aperture wide open before anything is stopped down.

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No; just changing metering mode will not affect focus on any camera that I'm aware of. If the metering resulted in different aperture or shutter speed, those might have an effect, but everything came out the same regardless of mode, right? (You don't mention shutter speed; I assume that none of them have a significant difference there.) Therefore, as suggested in the comments, the most likely culprit is simply that results are inconsistent and your sample size too small, with the center-weighted result just being most lucky.

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