Sigma 30mm f1.4 strange circle appearing

Started Jan 7, 2019 | Discussions thread
Alex_pv Junior Member • Posts: 29
Re: Sigma 30mm f1.4 strange circle appearing

I've seen things like this before due to big regions of the front element with coating stripped off (causing darker regions), but not with that perfect circular shape.

As already stated here by some, check the camera settings for lens correction, specially for vignetting control.

Next step would be checking if there are differences in the color of reflections when pointing the front element to a light source. If the color of the reflection in the front element changes too much from the center to the borders (except on the very edge, which is OK), the coatings may be defective - something that I never seen on a lens, but I've seen on filters. If this is the case, and given the output you are showing, you'll be able to see a brighter reflection in the center, and almost a "frontier" where the bright reflection turns into a dimmer reflection.

If you find what was causing that, let us know - very curious here.

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