Originally posted by Sunburn That service is only available between mounts that are already manufactured in a specific lens model. For example, let's say Sigma comes out with a new 50mm macro. They list it for Canon and Sony mounts, for some reason they decide not to sell it for Nikon. You couldn't use that service to slap on a Nikon mount.
It's disappointing that I can't get new Sigma lenses for my Pentax, but it's understandable. They've never tested the lens for firmware compatibility, mirror box clearance, aperture coupling, etc.