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I just bought me a Sigma 10-20 and have a few questions. I've noticed that there is light fall off on the edges. Is this normal? How does one capture a picture and have everything look evenly lit?

Ivan Watkins wrote:I just bought me a Sigma 10-20 and have a few questions. I've noticed that there is light fall-off on the edges. Is this normal?

Yes, a certain degree of light fall-off (also called vignetting) is normal in wide-angle lenses. I think you've been warned that the Sigma 10-20 mm DC lens has somewhat stronger fall-off than e. g. the Tamron/Konica-Minolta/Sony 11-18 mm. This is not perfectly free of vignetting either but it's so low even at full aperture it usually will go unnoticed.

Ivan Watkins wrote:How does one capture a picture and have everything look evenly lit?

Vignetting usually is strongest at full aperture. Stop the lens down to f/8 or f/11, then vignetting should be greatly reduced, if not gone entirely. Also avoid under-exposure because that tends to emphasize any vignetting. Finally you can always use post-processing software to remove vignetting, for example the Lens Correction filter in Photoshop.

By the way, be aware that there are cases which may look like lens light fall-off but aren't. In particular blue skies, shot with wide-angle lenses, often get rendered darker near the frame's corners which is due to the complex nature of celestial light. That also is the reason why blue sky is an inappropriate subject entirely to test lenses for vignetting.

-- Olaf

The Sigma 10-20 has it's limitations, but if there is enough light to stop down, it's a fun lens:









All pics with KM 5D

those are all nice shot... man been reading so much text the colours almost knocked me off my chair. How do you lose a lens? when you said lost it in other post I though you meant.. it got run over or something. I'm so paranoid when I change lenses.. it like I have 3 hands.

Great pictures guys.

Okay, I'm embarassed to say this but my really bad initial experiences were due to my own user error. I had my EV Comp set at -1.5 stops because I was using flash at another shoot and wanted to shoot that much above ambient. Well naturally, like any other person I forgot to reset my EV and thus everything was being grossly underexposed.. thus the horrible light fall off and vignetting. I'm good to go now and might post some images once I get any worthy of posting.

We live, we learn.....

Ivan Watkins wrote:I just bought me a Sigma 10-20 and have a few questions. I've noticed that there is light fall off on the edges. Is this normal? How does one capture a picture and have everything look evenly lit?

It's the first lens I've had which sometimes shows annoying vignetting. That may be because it's the widest lens I've ever had

I've found that PTLens, which is very good at correcting the geometric distortions of this lens, and pretty good at reducing its occasional chromatic aberrations, is also pretty good at correcting its occasional vignetting.

PTLens URL:
http://epaperpress.com/ptlens/

I have recently added the Sigma 10-20 to my bag, and this is one of my first attempts with it.


I posted another from the same location here

Congratulations Brian.
Nice shooting and I like the clouds much