I have been having a problem with my camera and the sigma lenses that came with my standard SLR EOS Rebel. I get a err 99 message every time I try to take a picture with my Sigma 80-300 lens. I have read a few sites, and everyone says that it is dirty contacts. I have cleaned the contacts multiple times. The only way to get a picture is by zooming to the max, and putting it on the action setting. Everything works great. Err 99: In your owners mauual on page 157 An error other than the above has accured,
Remove and reinstall the battery.
This error may occur if you use a non Canon lense and the camera or lense, does not operate properly as a result.
Some of the older lenses are not compatible with the XT. Try using the Manual focus, and see if that works. Hope this helps. older Sigma's have issues with newer EOS bodies. Check with newer sigma lens or another brand and you'll do fine. | 