Shadow arc in photos using 10-24 Sigma lens

[Sue G]

Hello,
Can someone help me please?
I have just started using a 10-24 Sigma lens but I seem to get a darker arc in the sky just right of centre in most photos.What could this be causing this issue ?

I have a uv filter on the lens and use the lens hood that came with the lens. The lens was second hand - could it be faulty ?

Look forward to receiving your thoughts on this, please.

Sue

[OsmosisStudios]

Examples are necessary. If it's a darkening of the sky, it could be polarization. The sky isnt uniform, and will be darker or lighter blue depending on where the sun is. This is an issue with ultra-wide lenses and the big reason people often recommend NOT using a circular polarizer on such a lens.

[Sue G]

Here are 2 basic images - the day was overcast and you can see the darker arc to the right of centre in both images. I have had the same arc on sunny pictures too.

Look forward to hearing what you think is happening.

Thanks !

[Doug Pardee]

Bad juju.

On the surface of it, that looks like a shutter problem. Nothing to do with the lens.

What kind of camera is this? And can you give us the EXIF information for those shots? At least the shutter speeds that were used? It doesn't look like a Canon (the arc on a Canon is less curved and more symmetrical), and I'll guess that the shutter speeds were pretty high (1/1000 or faster).

If it was a light streak instead of a dark one, you'd be looking at a light leak in the shutter, which would mean shutter replacement time.

Since this is a dark streak, it could just be some crud that is riding on one of the shutter curtains.

[OsmosisStudios]

Originally Posted by Doug Pardee

Bad juju.

On the surface of it, that looks like a shutter problem. Nothing to do with the lens.

Bingo. Shutter is dying.

[Sue G]

Thank you both - I raised the mirror and saw a hair across the sensor - case solved !

I was convinced it was the lens so you pointed me in the right direction !

Sue