Thanks for all the responses.
Originally posted by Ash So we're now talking about global overexposure with your copy of the Sigma.
Sample images here with EXIF intact would help with the comparison.
Also have the camera on tripod shooting with the two lenses with everything the same (WB, subject, aperture, lighting) and there will be a more accurate picture of the issue.
I did use the tripod, and I tried to set up exactly the same image. Posting images exceeds my digital knowledge, I am afraid.
Originally posted by pop4 I've got the Sigma 17-50/2.8 and I haven't notice any overexposure issues with it. Granted, I haven't done any thorough testing with it, but all I do is go out and use it to take photos.
I will be taking some actual photos this week. I wasn't planning to spend the first two weeks with my new camera testing lenses. I have to decide which lens today. The Sigma is sharper, but seems to have some problems, most of which I can deal with by changing settings, but this is inconvenient at best. The Pentax has CA issues that I don't know how to fix easily (I do not see that the in-camera correction is fixing the blues fringes). The Pentax costs somewhat more ($900 vs. $670) and interferes more with the built-in flash. I called both Sigma and Pentax, and sent images, but neither company is providing much help.