my picture shows huge black ring

[appletrees]

I just got a brand new 5Dmk3 last week and put sigma 50mm 1.4 on it. There were huge black circles appeared on my pictures after taking few testing shots.( two pictures had the circles)

Would anyone know what is causing this problem? Is it the camera or the  lense? Both are too new to me. So I am perplexed.

I have searched the internet but could not find anythng similar to my problem. Thank you!!

[cicopo]

Just to help people looking at the sample did you have a filter on the lens or was it just the bare lens? If you do have a filter see what it does without it.

[appletrees]

Thank you cicopo, for your answer.

I tried both with and without the filter after posting. Now there are circles on all of my pictures.

[TCampbell]

Given a the digital sensor will read out the pixels in rows and columns and this circular pattern matches the shape of the image circle as projected by the lens, my inclination is to believe that this is being projected onto the sensor by the lens and is not caused by the camera or sensor.  

Do you have any other lenses you can use to test?

[WahoGT]

My guess is one of the elements in the lens is misaligned. I can't think if a reason the body would do that to an image.
Try another lens if you can.

[appletrees]

Thank you all for your inputs. I tried with another lens and so far only the sigma is showing that hard line circles. Hope it is just the problem of the sigma lens not the body. I am sending the sigma lens back today.

[diverhank]

Out of curiosity, is your sigma a DG or DC?  I don't know much about non-Canon lenses but I read that DC models are for cropped cameras only and something like you're seeing will happen with full frame cameras like a 5D3.  DG lenses should not have this problem.

[appletrees]

The sigma lens is DG which is for FF. If it was for Crop bodies, it should have shown the vignetting on the 4 corners of the photos. But the circles I got were not vignetting type which you can see from the picture. Never seen anything like this before.

[amfoto1]

All Sigma 50/1.4 are DG (full frame).

The Sigma 30/1.4 is a DC lens (crop only).

The OP's problem is really weird. I've never seen anything like that. It's not a sensor or shutter problem. It also doesn't look like a lens issue, because those are usually out of focus.

It almost looks as if a Fresnel lens (such as is used in some focusing screens) is in front of the sensor. The sharpness of the focus of the black circles might be a clue. I'd use the camera's manual cleaning setting to open the shutter without the lens on, and inspect the filter in front of the sensor.... Brand new camera, maybe it has a fault. Only problem is, it sounds as if this issue isn't on all images, happens erratically. If there were actual marks on the anti-alias filter, I'd expect the fault to show up in every image, though it might vary a little depending upon light intensity. Erratic appearance of the fault in only a few images suggests a bad electronic component, but I've never seen one that draws circles on images!

[appletrees]

I just opened the pictures with the rings(raw format) with Photoshop ACR. Strangely enough those rings are gone when it is opened.  But from the original raw file(of course Jpeg from camera too) does show the rings.  Getting stranger... I would not know what could cause this with my limited knowledge.