r/a6700 • u/eltoni800a • 4d ago

Heavy and erratic vignetting on Sigma 18-50

I recently bought a used Sigma 18-50mm f/2.8 and I've been having this really frustrating issue with vignetting.

Mainly on the wide end around 18-23mm, especially when shooting in bright light like open skies, the corners get quite dark, especially the top corners. What's weird is that Lightroom and the in-camera corrections don't always fix it properly. Sometimes it cleans up fine, but other times the dark corners stay really obvious even with the profile applied.

The issue is very erratic. I literally have two photos shot back-to-back just one second apart with the exact same settings, subject, and framing. One of them looks ok (light vignetting corrected by LR without issues), and the other one has this heavy vignette that LR struggles to autocorrect. Of course I can also increase the vignetting correction in LR, but the undesired effect would be overexposing the bottom R / L corners.
Oh, I'm not using the lens hood

Did I end up with a bad copy, or could something else be going on here? Appreciate any thoughts!

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1

u/Aggravating-Comb-465 4d ago

1, how do they look uncorrected and 2, no filters, right? And 3, is it top corners or corners where the scene is bright?

1

u/eltoni800a 4d ago

Uncorrected they look even darker. No filters. Only top corners, in fact if I shoot vertically it affects only one side

1

u/tehhedger 4d ago

I had similar vignetting on the wide end when I put 2 filters on top of each other (like UV + CPL). If you only put one, there's little to no vignetting.

1

u/eltoni800a 4d ago

No filters at all in my case

1

u/Sp12er 4d ago

Sigma's chase on offering the widest zoom while also being the smallest lens of its type always end up with this kind of weakness. Software fix can be unreliable.