Originally posted by monochrome It is a mystery. I suppose there is enough demand to continue making the lens elements, but why keep using SMC and making the ancient plastic barrels?
I don't think it's that big of a mystery at all. As most of us know, camera and lens makers tend to produce products in batches and may or may not produce additional batches as needed. Pentax has always had this lens in stock overseas and now they have a full-frame camera for sale in the U.S. So they brought in a batch of the FA 35mm f/2.0 lenses in order to serve that market in the short term.
Pentax may be working on a more-premium 35mm lens for the K-1. But that doesn't do them any good right now... and many Pentaxians can't afford or won't buy the FA 31 -- at least not until it's brought up to modern standards or a replacement is released.
As an aside, the FA 35mm f/2.0 is a very good lens - and was a fabulous deal when it was first introduced. But its price has steadily risen over the years and its reputation grew from that of one of the better plastic-fantastic normal primes to that of near Limited quality. I'm not sure it deserves such a reputation. It has only six aperture blades and the newer DA 35mm f/2.4 is the same optical formula. As for the differences in aperture between the two pieces of glass, those who have used both extensively will tell you the the FA behaves a bit more like an f2.2 lens - and so does the DA version.
I'm not putting down the FA 35mm f/2.0. I think it's a decent option for K-1 owners in the short-to-medium term. But let's remember what its mission always was. And its reappearance in the U.S. market at this time makes all the sense in the world.