Typical sigma incompatability symptoms?

[ron chappel]

I've read many times about sigma lenses needing to be rechipped to work on newer bodies but never though alot about how the errors occour

I ask because i had an ancient sigma/eos lens once that had a fluttering aperture.I got it with a bunch of repair lenses and thought at the time that it was just broken
But recently i aquired a sigma 70-300 DL macro super lens that shows similar syptoms.The lens will work perfectly on the 300D until i try to stop down the aperture-the the error99 signal appears and i have to restart the camera to get it working again
I'll contact sigma tomorrow about rechipping it - i'm just curious if anyone else noticed a pattern to the sigma incompatability thing?Is it allways the aperture that sets it off?
Can affected lenses generally be used wide open?

[chris maddock]

It usually is the aperture, I believe.
I have heard that the problem (or part of it) is that Canon reduced the voltage supplied to the aperture control in the lens - whilst the older Canon lenses are happy with the reductions, older Sigmas are not. Whether that's true or not, it is a plausible possibilty.

KRs
Chris

[eric1]

Ron, i had 2 sigma lenses, and they behaved just as you described. only worked at widest AP. Sigma said my 400 was too old to be rechipped, so i bought the Canon.