What exactly do the different letters in the Pentax lens designations mean? I've been looking for an explanation on the K mount info page and other places, but not found anything...
I understand the difference between an "M" and "A" lens, of course, and I know an "FA" lens has autofocus. But how about "F"? Or "K"? And are there others?
"F" was the first generation of Pentax autofocus lenses. They lack one or two features such as MTF transfer. a "K" lens is one of the original series of Pentax bayonet lenses. Feature-wise they are identical to the M series, but they are generally larger and heavier, and in many cases of slightly better quality than their M-series equivalents.
There's also the FA-J series (FA with no aperture ring), DA (focal plane coverage to suit APS-size digital sensors; liable to vignette on 35mm) and whatever those new macro lenses are - D-FA or something? Oh, and all the M42 (screw-mount) lenses - Takumar and Super Takumar.
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