Sigma confusion!

I have a Sigma f5.6 400mm APO telephoto lens that I am trying to use with my Canon EOS 30, a D60 and a recently purchased 10D.

With the D60, the lens works OK, the AF works and the lens stops down right through from f5.6 to f22. With the 10D however, the AF works OK, but I can only use it at f5.6 otherwise I get an 'err' message.

Is this normal?, I'm lookong to buy the f4.0 300mm version of the same lens, so will I have the same problems with this lens as well?

I think it is down to the fact the lens is an older version and cannot communicate with the newer bodies. Suprised it works with the D60 though, must be lucky!

Which 300mm F4 you looking at?
The 100-300mm F4 EX works OK on the 10D

The communication protocol between the camera body & lens is different on the D60 and later Canon DSLR's. AFAIK, Canon do not make their communication protocol public so 3rd party manufacturers have to reverse engineer the communication data to incorporate it in their lens. The Sigma lens was built before these newer cameras were made so the information required to fully work isn't programmed into the chip on the lens. Sigma do re-chip lenses for a modest cost (I believe it is around £33). I had a similar problem with a Sigma 70-210mm but managed to sell it on to a film camera user for a very small profit. The error that lens gave was err99.

I take it this is the older non-HSM version of the Sigma 400/5.6 APO. It worked well on my older Canon Rebel G and EOS 3, cameras, but I stopped using it when I got the Sigma 50-500 so I gave it to my nephew who needed a telephoto lens for the wildlife biology course he was taking. It would not work on his newer Canon EOS film camera. He sent it to the Canadian Sigma distributor to be re-chipped, but was told that a new chip has not been developed for that old lens. It is considered obsolete.