Why doesn’t my Canon 24-70mm image look pin-sharp at 100%?
Asked 10/27/2014
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2 answers
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I’m testing a Canon EF 24-70mm on a Canon 5D Mark III and the results look softer than I expected. The photo was taken from a solid tripod on an almost windless day using a remote release.
Settings:
- 70mm
- ISO 100
- 1/100 sec
- f/7.1
The trees were about 150m away, and I focused at about 35m. When I inspect the RAW file at 100%, it doesn’t look “pin sharp,” although it improves with sharpening in Adobe Camera Raw.
Are my expectations unrealistic for a zoom lens and a 22MP full-frame file viewed at 100%? Or is there a likely cause such as focus placement, field curvature, lens performance, or autofocus calibration?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
7
It doesn't look too bad to me.
You have to consider that when you're looking at a 5D mkIII image at 100%, that amounts to a considerable enlargement. It's rare to get something really pin sharp at that magnification.
The focus point is quite forward so the trees in the centre of the frame are at or near the far limit of the DOF. That combined with the softish lighting is probably giving the effect you're seeing here.
The far left and right sides look about the same, so no evidence for any decentring, they just look out of focus to me, with a touch of lateral chromatic aberration.
It's important to be aware of field curvature, when making test shots I would live view focus in the centre and then again in each of the four corners and compare the results. That should rule out any DOF / field curvature effects.
Originally by user1375. Source · Licensed CC BY-SA 4.0
user1375
11y ago
0
Generated from our catalog & community — verify before relying on it.
Probably a mix of normal expectations and focus placement, not a defective lens.
At 100% on a 5D Mark III, you’re viewing a very large enlargement, so it’s normal that images won’t always look perfectly “pixel sharp.” A 24-70mm zoom—especially compared with top primes or Canon’s sharper 24-70mm f/2.8 II—also won’t usually render every detail razor crisp at that magnification.
Your focus distance may be the bigger issue: if the trees are around 150m away but focus was set at 35m, the trees could be near the far limit of depth of field rather than at optimum focus. That can make them look slightly soft, especially in flatter light. The similar softness across the frame suggests ordinary focus/DOF limits rather than decentering.
There may also be some field curvature and a little lateral chromatic aberration.
What to try:
- Test again using live view focus directly on the distant subject.
- Compare center and corner focus to check field curvature.
- If using phase-detect AF, check autofocus microadjustment.
So yes: the image may be close to normal, and your expectations at 100% may be a bit high.
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AI11y ago
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