Why are my portrait subjects' eyes soft with a Canon EF 28-70mm f/2.8L on a 5D Mark III?
Asked 9/28/2018
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I’m using an older Canon EF 28-70mm f/2.8L on a Canon 5D Mark III for portraits. At 70mm with autofocus, the subject’s eyes often aren’t sharp and the face looks a little soft, while manual focus gives better results. I’m trying to figure out whether this is likely autofocus calibration, user technique, or something else. Can the 5D Mark III’s AF Microadjustment help, especially if the problem is mainly at the long end of the zoom?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
1
Since you're able to get desirable results with manual focus, you probably need to calibrate Auto-Focus Micro Adjustment (AFMA). It's not clear if the lens is front or back focusing since you don't specifically mention whether the nose is in focus, and it is easy to overlook. If you still have problems after calibrating AFMA, you may want to stop down the aperture a bit.
See The-Digital-Picture: AF Microadjustment Tips for details about the process.
Originally by user75526. Source · Licensed CC BY-SA 4.0
user75526
7y ago
0
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If manual focus is giving you sharp results, the lens is probably capable of good sharpness and the issue is more likely autofocus calibration than optical quality.
On the 5D Mark III, use AF Microadjustment (AFMA). If the problem shows up mostly at 70mm, the camera lets you adjust the telephoto end separately from the wide end, which is useful for zooms. Check whether focus is landing in front of or behind the eyes, then fine-tune accordingly.
Test carefully at both ends of the zoom and at one or two focal lengths in between. Errors are often more obvious at longer focal lengths, and the camera interpolates between the wide and tele settings, so adjusting one end can affect the middle.
If focus is still inconsistent after AFMA, try stopping down a bit. At 70mm and f/2.8, depth of field is quite shallow, so even small focus errors can make the eyes look soft.
In short: start with AFMA on the 5D Mark III, verify front- vs back-focus, and re-test before assuming the lens is faulty.
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AI7y ago
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