Originally posted by nater Tokina used to make K-Mount lenses, so you can still find them in places like ebay, but the last Tokina K-Mount lens was produced in 2002 - Tokina now co-develops some lenses with Pentax, so there are 'cousin' lenses available from Pentax that are very similar to some Tokina lenses,
specifically:
Wikipedia ain't always a fantasticaly detailed source.
To be more specific, Pentax developed the
DA10-17 fisheye
DA*16-50
DA*50-135
DA35ltd macro
DFA100 macro (slightly changed optical formula based on F/FA100 macro, see
Pentax Short Telephoto Prime Lenses)
Perhaps Tokina contributed somehow, but Pentax is the only company name on the patents, so I doubt that. It is more likely that Pentax has licensed the optical designs to Tokina. A quite common sort of deal historically between different lens makers. Tokina manufacturers their own versions, apply their own coating, and you don't get SDM and weather resistance on the DA* lenses. Also, at least the Tokina version of the 35ltd is very plastic and far from limited build quality. Obviously in this deal Pentax must be making money on Tokinas sales to Canikon users who buy these lenses and Tokina are forbidden to sell them with K mounts. Pentax would be a fool to let someone compete with low budget versions of their own designs.
In the same way, but vice verse, the DA12-24 is a Pentax build of a licensed Tokina design. Probably Tokina get their share of Pentax profit on that lens.
Simple as that. Lens history is full of this. But they would never talk openly about the details of the economical agreements.