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Nifty fifty STM - focus issues, or human error?

Started Nov 16, 2017 | Discussions thread
ZX11
ZX11 Veteran Member • Posts: 6,156
Re: Nifty fifty STM - focus issues, or human error?
1

47872Mike wrote:

I've just been testing my new 50 STM and am struggling with the same issues.
I tend to think it is not down to mechanical play since switching to live view nails focus every time, and using old-fashioned SLR AF nails focus on average a bit less than every other time, depending on light level (based on preliminary tests). Either that or the way the algorithm works excites the mechanical play and leads to the way focus doesn't come to rest at the same point each time you half press.
My tests were done at maximum aperture but I didn't notice an improvement when I tried a few with the lens stopped down after reading some comments here (other than a deepening of the zone of focus which somewhat masked the problem in some instances).

Yes, live view's AF system works better in challenging situations where the light isn't perfect and the focus is razor thin.

I think the expensive "L" lenses handle poor lighting better and control fringing better. That is one reason why they are worth the money. Cheaper lenses throws off the optical viewfinder auto focus system since they don't handle the light as well (blue/purple fringing and contrast).

My 50mm f1.4 hits all the time on my EOS R, which is always live view type AF. It missed almost all the time with when mounted on my T5i, which was through the optical viewfinder.

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