[howard g]

The lens compatibility page is a great idea- but I have lenses that work just fine on my k-50, that aren't there:
tamron ld 28-300 3.5-6.3 macro
takumar-f 70-200 4.0-5.6
vivitar 80-200 4.0 macro (manual focus)

Thought that you'd like to know.

[Adam]

Thanks! The Takumar F combo is here:
Pentax K-50 and Takumar-F 70-200mm F4-5.6 Compatibility | PentaxForums.com

As for the other lenses, they are not current, so they are not in our database. At the moment we are only indexing current third-party lenses, though we plan to add major legacy lenses in the future.