Originally posted by kooks Don't know if Canon & Nikon are, but recently in a interview with a Sony executive he said that Sony don't have any problem with third party lenses and they actually "help" companies to build them and give them the "rules" of how to do the appropiate mount... For Pentax it's a totally different story AFAIK, they have to do reverse engineering on their own.
Pentax, Canon, and Nikon are traditional optics companies that have been making lenses for roughly 100 years; Sony is an electronics company that purchased a traditional optics company, but seems to have tossed most of that and left it behind by now as they seem to be abandoning the A-mount. I treasure my Sony 10-20mm lens - actually both of them, since I had an EF-mount version several years before I came back to Pentax - but my K-mount version would have been even better if Sigma had been willing to purchase KAF3/KAF4-mount access from Pentax (*). Pentax's FF product would be better if Sigma and Tamron were willing to participate there, but that is true of new Canon and Nikon lenses also. So the only thing that makes Sony a "different story" is the low value they put on their mount.
(*) I wish my lens had an in-lens motor. I know Sigma could do that because the EF-mount version had that, of course, but I guess Sigma hadn't figured out KAF3 when they developed the lens I have. It was my decision to purchase the Sigma lens instead of saving up and purchasing a similar lens from Pentax.