Jim Strutz - Anchorage, AK , Dec 08, 2005; 02:52 a.m.
Sigma makes this lens with several different mounts. They make it in EF mount to fit the Canon EOS line, but also make it in Nikon, Pentax, Minolta and Sigma AF mounts. Do you know what camera brand that your Sigma lens is designed to fit? If not, can you post a picture of the lens mount?
Some lenses can be adapted to fit Canon EOS mount (Nikon for instance), but some cannot (Pentax for instance). In any case, it is hardly something that you are likely to want to do as you will be left with a lens that has no autofocus, and no aperture control at all. Some specialty lenses might be useful to use this way, but the Sigma 70-300 is not all that great to begin with.