Why are my landscape photos soft with a Canon Rebel T2i and Sigma 10-20mm f/3.5?
Asked 12/20/2016
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I’m shooting landscapes on a Canon Rebel T2i with a Sigma 10-20mm f/3.5 EX DC on a tripod, using a self-timer/shutter delay. My images still look soft and dull, even when I manually focus using the infinity mark or a depth-of-field app. I expected that at 10mm and around f/5.6, focusing a few meters away would keep most of the scene sharp, but my results are worse than expected. Stopping down further seems to make them look even blurrier.
I’ve also compared this to older photos from my kit lens, which look sharper, so I’m wondering whether I’m misunderstanding focusing at infinity, using the lens incorrectly, or whether this particular lens may have a problem.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
1
The Sigma 10-20 f/3.5 EX DC) has issues with lens quality specifically "sharpness degrading" and auto focus.
First, compare between manual focus and auto focus. Consider using a shutter release. Did the sharpness improve?
There may be an issue with the lens and may need to be sent back to Sigma for adjustment/calibration/correction.
From the Sigma 10-20mm f/3.5 EX DC HSM Lens Review: "With a wide open aperture, the Sigma 10-20mm f/3.5 EX DC HSM Lens is sharp in the center with sharpness degrading to somewhat soft in the frame corners. At f/5.6, the corners improve a noticeable amount - to very nicely sharp. I don't think that you will notice the improvement realized by stopping down beyond f/5.6."
"...the fixed maximum aperture allows a constant wide open aperture exposure setting to be maintained over the full focal length range of the lens... Unless you are using manual focus, focus accuracy is very important to final image quality"
Taking a step back... the lens is trying to capture the widest view angle and flatten it. The lens is also compensating for the small sensor and further manipulating the image. It's essentially making a orthographic projection and cramming it into a rectangle.
Update: Have you isolated the issue to lens or the camera? I recommend borrowing or testing a premium lens to make sure it is not a camera issue as well. Likewise for the camera. I know the Ti3 is much better than the Ti2 and that may be compounding the issue.
Originally by user52981. Source · Licensed CC BY-SA 4.0
user52981
9y ago
0
Generated from our catalog & community — verify before relying on it.
Two things stand out.
First, focusing at the infinity mark does not mean everything closer than infinity will be sharp. It means the lens is focused on very distant subjects. For landscapes, you usually want to focus at an appropriate distance into the scene (often near the hyperfocal distance), not simply set the lens to infinity.
Second, your sample and description suggest your particular lens may also have a calibration or optical issue. The Sigma 10-20mm f/3.5 is generally expected to be reasonably sharp, especially around f/5.6, with corners improving when stopped down from wide open. Going much beyond f/5.6 may not help much, and very small apertures can look softer due to diffraction.
What to try:
- Compare autofocus vs manual focus.
- Test the lens on another camera body if possible.
- Shoot controlled tests at 10mm around f/5.6.
- Use a remote release or timer, which you already are.
If it remains unusually soft compared with your kit lens, the most likely conclusion is that this copy needs calibration/service from Sigma rather than that you’re doing everything wrong.
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UniqueBot
AI9y ago
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