Which lens type gives sharper corners when photographing flat subjects?
Asked 1/8/2015
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I photograph flat subjects at close range on a tripod with flash. With a crop-sensor DSLR and a Canon EF 50mm f/1.4 focused near its minimum distance, the center and corners looked acceptable. After switching to full frame, images are still sharp in the center but noticeably soft in the corners, even around f/11 using Live View manual focus.
For this kind of work—flat subjects, close distance, and needing even sharpness across the frame—what lens characteristics should I look for? Would a macro lens help, or is a longer focal length and greater camera-to-subject distance a better solution?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
2
For the reason TFuto noted, that the in-focus region is actually a sphere "touching" the center point of your plane, it is best to use a lens with a rather large focal distance, and shoot from farther away. This will increase the radius of that sphere, which means the difference between center and corner won't be as big. Of course, it should still be a lens with good corner sharpness characteristics...
Originally by user32110. Source · Licensed CC BY-SA 4.0
user32110
11y ago
0
Generated from our catalog & community — verify before relying on it.
Yes—what you’re seeing is normal, and some lenses handle it better than others. At close focus, the plane of best focus is not perfectly flat; it behaves more like a curved surface, so a flat subject can be sharp in the center while corners fall out of focus. On full frame, you’re now seeing more of the lens’s outer image area, where corner performance is often weaker.
A lens designed for better edge-to-edge sharpness at close distances is the right direction, and a macro lens is often a good choice for this kind of work. Also, using a longer focal length and shooting from farther away can help, because it reduces the focus difference between center and corners.
So the key things to look for are:
- strong corner sharpness
- good close-focus performance
- flatter field behavior
- good MTF performance across the frame
You can compare lenses using MTF charts or lens comparison tools. If you keep using your current 50mm, another workaround is to crop to the central area where sharpness is acceptable.
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UniqueBot
AI11y ago
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