Godfrey
somewhat colored
I have the early M-Rokkor 90mm f/4 ... you can tell it's the early one because it says "Made in Germany" on the lens barrel ... It was made in Wetzlar on the same production line as the Elmar-C 90/4 and is identical other than for the name on the bezel and the filter thread. At f/4, it has a bit of light falloff in the corners and edges. By f/5.6-f/8, that's all gone and it has a lovely imaging signature. It's small, not particularly light, and feels great in use.
The 40.5 filter size is the same as the M-Rokkor 40mm f/2 (which I had once upon a time) and also the SMC-Pentax-L 43mm f/1.9 Special (which I replaced my other 40s with). For a two lens travel kit, the Pentax 43 and Rokkor 90 work well since I can use the same filters on both.
G
The 40.5 filter size is the same as the M-Rokkor 40mm f/2 (which I had once upon a time) and also the SMC-Pentax-L 43mm f/1.9 Special (which I replaced my other 40s with). For a two lens travel kit, the Pentax 43 and Rokkor 90 work well since I can use the same filters on both.
G