Tiffen still offers a wide selection of 2x2" glass filters and here in the US, B&H PhotoVideo carries them as well as some others.
Go to http://www.bhphotovideo.com and search on "2x2" filter" to see 11 pages of filters listed.
A question I have about the Kinoptik 5.7mm lens is whether a filter (or glass blank) is required to be installed in order for the lens to focus correctly?
I recently bought a PL mount version of the Kinoptik off of eBay without any filters and the lens is not focused at all. Everything is a complete blur.
Thanks for any info.
