Can anyone tell me what the difference is between the Sigma 70-200mm 2.8 APO HSM & the one with DG in the title? I thought DG stood for digital?? I've been looking at the APO HSM version & wondering if I'd have any problems using it with my Canon 40D? I know some older Sigma lenses can bring up the err message after a little while of using them unless you get them chipped, so I wanted to check as I've seen one for about £300 & thought I may buy it.
Thanks for any help you can offer.