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Help needed: overexposed pictures with Sigma 18-50 1:2.8 DC EX


New Member

I have an issue I recently noticed on my hiking vacation in the swiss alps. Some time ago I replaced my Canon EOS 20D with the new 550D... very happy so far. I kept both my lenses, one of them is the Sigma 18-50 / 1:2,8 / DC EX. I never had a problem with the 20D.

Now, when I take some pictures at excellent light conditions (very sunny!!), some pictures are completely overexposed. If you compare the 2 attached pictures, both are taken at the same time in automatic mode (P) with the Sigma lens:

Taken with: Canon EOS 550D and Sigma 18-50 / 1:2,8 / DC EX

overexposed picture: focal length: 38
exposure time: 1/640 sec
aperture: f/9

good picture: focal length: 50
exposure time: 1/640 sec
aperture: f/9

Exposure and aperture are the same, so I suspect an issue with the lens (some kind of partial incompatibility?).
Also I am pretty sure that I never noticed such a tremendous overexposure with my other lens (Canon 55-250 / 1:4-5,6 / IS).

Anybody has a more precise idea what is going on here ?

Thanks for any help


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Well-Known Member
It looks like it was a semi-overcast day...maybe the sun peeked out from behind a cloud...I checked your EXF data...they both mirror each other...the only thing I did see is that you had your...

You had the exposure mode as auto...maybe the camera just had a little hickup....?:z04_pc2:

Can you reproduce the issue...??

On another note....the lens is an EX have a 5 year Sigma might want to send it in to be calibrated and specked out...

Tony C....:z04_cowboy: