Only two 50mm f/2 K-mount primes stand out as "worth getting over an f/1.4": the XR Rikenon and the Rikenon P. I briefly owned the P and was startled at its corner-to-corner sharpness at f/2.8. Either model can be found for $20 to $30. Their only drawbacks are that an f/2 lens is harder to focus than an f/1.4, and both Rikenons are single-coated and made of aluminum.
Only one 50/1.4 K-mount lens that I've used delivers comparable corner-to-corner sharpness at f/2.8: the multicoated Rikenon P. I've just received my first two rolls in which I used my Rikenon P 50/1.4, including several shots taken at f/2.8. The films were Royal Gold 100 and Gold Max 400. All I can say is, Wow. Since then I've shot the Rikenon at f/2, but I haven't finished that roll. The Pentax SMC 50/1.4F and FA are probably the only K mount 50s as sharp at f/2.8, at least in the corners. [EMAIL PROTECTED]
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