Focus accuracy V light levels on 50mm f/1.8

Started Aug 31, 2014 | Discussions thread
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cberry Senior Member • Posts: 1,127
Focus accuracy V light levels on 50mm f/1.8

I've just ran some test shots on a 650D + 50mm f/1.8 and 18-135mm IS STM as something was bothering me with the 50mm.

Whenever I focussed on eyes in relatively low light, the image looked soft.

I didn't think it was the lens.

So I tried test shots with a pattern printed on paper against the wall in front of the camera.

Result: at f/1.8 what the camera thinks is in focus isn't necessarily what I want especially in low light.

So, I tried the STM lens in the same environment - incredibly sharp by comparison and spot on focus every time.

Next I tried live-view - focus was very slow on the 50mm but spot-on - on the STM lens, considerably faster and again spot on even in very low light.

Is this just a problem I have to live with with the 50mm or does it sound like there's something bad going on? I'm not impressed with the focus accuracy on the 50mm although the sharpness is amazing.


 cberry's gear list:cberry's gear list
Canon PowerShot G7 X Canon EOS 70D Canon EF 70-200mm f/4L IS USM Canon EF-S 18-135mm f/3.5-5.6 IS STM Canon EF-S 24mm F2.8 STM +3 more
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