sigma 500mm apo 1:7.2 on 20d

hi this is my first posting of new thread. any way how it all started i used to do film with my 50e and i had the 500mm 1:7.2. so i thought i will give it ago on my 20d. done some tests first off all i put it on auto ERROR99 so then i go in av set aperture at f7.2 still got ERROR99 then i tryed to set to f5.6 wow it worked perfectly all the time. i have herd a lot of people have this problem with older lenses. any way this old sigma worked. i thought i had to chuck this lens in the bin.

I'm glad it worked for you, & Welcome to POTN!

I'm moving this to "Lenses".

Quick sell it on eBay. Sigma no longer rechips old lenses. You will not be able to use it on your 20D - at anything other than wide open.

thanks for the advice sad advice. this lens cost me alot when i brought it it done some good work when i used on film. when it worked on f5.6 on me 20d i was very pleased but it has to be kept open wide aperture.i wonder how many people get the same problem this lens is in great condition