Yes, and yes. You have to focus and set aperture manually, but other than that they will work fine.

Thanks very much.  Anyone know about the adaptors sold at http://www.cameraquest.com/frames/4saleReos.htm

The claim is that they are better than the Novoflex adaptors.  True?

                       Dan

I read that the Canon EOS (& all digis) registration (which relates to the distance between the rear element and the focal plane or CMOS, doesn't it?) is 44mm and the Nikon and Leica R, 46.5mm and 47mm respectively.  Does that mean that Nikon and Leica R lenses can be used - at least, manually - on my 20D?  And if so, are there ready-made adaptors available?
                                Thanks, Dan

Try this link to B&H for example
http://www.bhphotovideo.com/bnh....418&ac=

There are adaptors for using almost every 35mm format lens with an aperture ring a Canon EOS mount. (Edited: I originally suggested that DX lenses could work on the 1.6x bodies, but I just checked and they are all G lenses, with no aperture ring.)

I have read that Canon deliberately made the EOS registration distance short enough to allow the use of Nikon lenses via adaptors, and advertised this in a campaign to get pros to switch from Nikon to Canon EOS.

The three main brands I've heard of are Cameraquest, Novoflex, and Zoerk. But I've not used any, so I can't really comment further.