Yes, there is a Pentax-K to Canon EF (EOS) mount adapter, available from "Mr.Rolfo". I suggest that you contact him directly at [EMAIL PROTECTED] for more info. I have two of these adapters (which I call the Keos mount), one on a SMC Pentax 18/3.5 and the other on a SMC Pentax 500/4.5
I'll be releasing a major update of my web site in a month or so, and it will include pics of the Keos adapter on these lenses. Rolf will probably send you his .pdf instruction file with pics and German text if you contact him. I am completely satisfied with this product and may buy more in the future, but once you get into Canon L-series lenses, its hard to "go back" - my SMCP 18/3.5 is now a backup for an EF L zoom lens. In order to use this Keos adapter, or the SRB conversion process described by Cotty, your lens needs to undergo an aperture leverectomy operation to remove the aperture lever and its protective tab (if present), as the EOS body mirror box is too shallow around the edges to fit the lens with the aperture lever. As Cotty said, the lens then has a manual aperture, which means "stop down" metering (at least, you never need to use the DOF button). My 18/3.5 has been de-levered, but the 500/4.5 is already a manual aperture in its "as built" condition, so no mods were required. The Keos adapter is a very slender, solid metal ring with a Pentax K body mount on the inside surface and a Canon EF lens mount on the outside. The pentax K lens mount fits into the adapter, rotates about 30 degrees and is secured from rotating back by a single, very small set screw. The lens with-adapter-attached then mounts on the EOS body as a normal EF lens (but manual focus and aperture). The Keos adapter is easy to take off the lens, just be careful not to drop the set screw, it's very, very small. The adapter is strong and secure. I'm not sure if it would be a good idea to use it with a really heavy lens hanging from a camera on a shoulder strap attached to the camera body, but nobody would do that even on a real Pentax body, right ? My 18/3.5 is very light, and with the 500/4.5, you carry the lens, not the camera. You should know that you cannot simply remove the aperture lever for use with Canon bodies and later replace it for use with Pentax bodies (at least for my 18/3.5), as the "inside" part of the aperture control mechanism is required to control the aperture with the aperture ring. If you remove this mechanism entirely, then the aperture cannot be controlled at all. It would be nice to have two aperture control assemblies, one with the lever and one without. For more info on the "Keos" adapter (my name for Mr.Rolfo's product), send email to Rolfo at [EMAIL PROTECTED] For more information on the conversion described by Cotty, you can contact SRB directly through Ian R Broomhead [EMAIL PROTECTED], and see their web site at www.srbfilm.co.uk For more info on using non-EF lenses on Canon EOS bodies, I highly recommend that you should read NK Guy's article "Using manual lenses and telescopes with EOS cameras." at http://photonotes.org/articles/eos-manual-lenses/ ciao for niao, Jim www.jcolwell.ca
