I have an old Sigma 70-300mm lens which I gather needs ‘re-chipping’ to work on my new Canon digital SLR. Can this be done?

The majority of lenses we can rechip. However there are a few older lenses which we are unable to re-chip due to parts no longer being available. In order to answer your question, we need to determine which 70-300mm lens you have. If you look at the lens, is the Macro switch held on by two screws? Or does it state ‘Super’ on the unit?