Originally posted by thibs And your point is?
Yes, Pentax and Tokina do share optical designs (being a good thing or not is all a different discussion IMO), most (but two) being Pentax designs.
Fukk me for posting some specifics on the Tokina-Pentax-Hoya connections. However, if you look at it closely, the connections are actually tighter since Hoya acquired Pentax. Tokina shares several, in fact the majority of its optical formulae from its current line up with Pentax. Tokina's previous line up did not. Finally, there are some designs that Tokina took the lead on even though most Pentax did. That was my point relative to the OP.