It my understanding that the DG designation means they have been optimized for digital cameras and will still work on all of the Canon bodies of the past. That is assuming no chip problems. I would recommend checking at a local camera store to see if a lens you're interested in will work with the Elan. I personally use a Canon 10D and 20D and use two sigma lens, 17-125 f3.5-6.3 and 70-200 f2.8. Both have worked great on both cameras with no problems with compatibility. I did have to send my 17-125 back for repair and apparently they think it was exposed to sea water (I was in the VI, so that may have been it). The 17-125 is a DG lens while the 70-200 is the older non-dg version. But in head to head tests with the Canon 70-200 f2.8 it the version I have was rated as virtual dead heat.
Be aware, however, that there is another designation of Sigma Digital lens called DC. The DC lens are only compatible with the Canon cameras that have the 1.6 x crop factor.
Here is a photo with each lens above:
Re: Sigma Lens Question
Re: Sigma Lens Question
cheers,
rfs