Why do my shots look less sharp at infinity than the zoomed Live View image?

Question

Using a Canon EOS 650D, I’m having trouble getting truly sharp focus on very distant subjects, especially at wider apertures. I’ve tested with a Canon EF 50mm f/1.4, the EF-S 18-55mm IS II, and also a fully manual lens. I focus manually using magnified Live View, but the final image can still look worse than what I saw on screen.

I wondered whether this could mean a flange-distance or sensor-position problem, but I’m also aware it could be technique or lens behavior. Is there a reliable way to check whether this is a camera-body issue versus normal Live View/manual-focus behavior when shooting at or near infinity?

user1375 · Answer

I think there's a couple of things going on here. Firstly some lenses exhibit focus shift, whereby the plane of sharpest focus moves as the lens is stopped down (this is usually due to residual spherical aberrations).

Secondly camera live view feeds are subject to certain restrictions in the area that can be read from the sensor in real time, and will sometimes interpolate the image at certain magnification settings. The upshot is the live view image is often less sharp than it should be.

Live view typically works with the lens wide open. So it may be the case that the live-view looks out of focus simply because the lens is soft wide open (the 50 f/1.4 definitely is) and the live view feed is softer than it should be. When you take an image you get focus shift and so the final image is also soft.

I would suggest you focus stopped down (there should be an option for this somewhere) and take an image to see if that fixes the problem.

Why do my shots look less sharp at infinity than the zoomed Live View image?

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