How does focus-and-recompose affect sharpness when using a lens wide open?
Asked 6/22/2019
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I often use focus-and-recompose for portraits so I can place the subject off-center. Some lenses are sharpest in the center and softer toward the edges, especially at wide apertures. If I focus on a person and then recompose so they end up near the side of the frame at the lens’s widest aperture, will the portrait be less sharp because of the lens’s edge softness, or is focus error from recomposing the bigger issue?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
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The problem with lenses wide open (gross generalization coming) is softness moving toward the corners - and this will be there no matter the exactness of your focus.
The problem with focus and recompose is that it’s very easy to minutely change the distance to which you are focusing...not that you’re actually refocusing but that by changing the camera angle, the distance to your new subject is minutely different.
The problems compound when using a lens at a large aperture where DoF is mere millimeters anyway (now your shot is OOF from sloppy recompose technique) and compounded by putting the subject in a soft portion of the lens.
All that being said, I’ve missed more shots to OOF than lens sharpness. Of the two, that’s the more critical issue in my book.
Originally by user67377. Source · Licensed CC BY-SA 4.0
user67377
7y ago
0
Generated from our catalog & community — verify before relying on it.
Both can reduce sharpness, but focus error from recomposing is usually the bigger problem at wide apertures.
When you focus and then tilt the camera to recompose, the subject may no longer sit on the same focus plane. At shallow depth of field—common in portraits shot wide open—even a tiny change in camera angle or subject distance can push the eyes out of focus.
Separately, many lenses are softer away from the center, especially wide open, so placing the subject near the edge can also reduce sharpness even if focus is correct.
Which matters more depends on depth of field, subject distance, focal length, and the lens’s field sharpness. In very shallow-DOF situations, missed focus is often the dominant issue. With more depth of field, edge softness may be more noticeable.
Practical takeaway: if possible, use an autofocus point closer to your intended subject position rather than focus-and-recompose, especially for close portraits at large apertures.
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