My friend is having Canon 350D/RebelXT Camera and using Canon 70-200 F/2.89 Lens regularly.
He is also having Sigma 170-500 (non DG) version lens which he was earlier using with his Film Cameras. This particular lens is giving problem.
Whne mounted on 350D and zoomed to 500 MM and clicked, it gives ERR99. I tried the same lens on my 30D but it works fine.
Initially we thought that it might be due to bad contacts or dirty pins, we cleaned it thoroughly but all in vain. The lens still give ERR99.
Can anyone guide me why it is happening.