I've just moved up to a 5D mk III from a 450D.
I have a collection of lenses built up over the years, so I thought I'd try them on the off chance they would work. I tried them once each, and mainly got an; "error camera cannot connect with the lens properly, please clean the lens contacts," message, so I desisted.
One of them, a Sigma UC zoom 28-105mm 1.4-5.6 which would be an ideal "walkabout" lens, worked but only intermittently, on the 5D.
Is using this lens a big no-no? Is there any way it can be made suitable? Or should I sell/bin it?
Thanks for any and all advice.