You're right about the 35/2 FA; I had forgotten about this autofocus lens.

I guess I stand corrected about the Sigma 50 macro being sharper than the 
Pentax 50/2.8 FA. It sharpness is nothing short of phenomenal. Yoshihiko 
Takinami writes: "This macro is excellent not only for macro work but also 
for normal use. Better than Sigma EX because the SMC coating is better.... 
In my experiences, FA50/2.8 macro seems the *sharpest* with great resolving 
power and contrast. And David Collett of Oxford University: "My top two 
sharpest primes (from a subjective rather than objective measurement) are 
the FA50/2.8 macro and my k35/3.5. My A50/1.4 is a pretty close third."

In favor of the Sigma, Tanya wrote, "Took the most 
three-dimensional-looking pictures I've ever seen." And there are also 
numerous superlatives, as I recall, by users at the various lens rating 
sites. I think Tanya's comment and others I've read left me with the 
impression that the Sigma was the macro to beat.

Now to the 135mm contest: Pentax 135/1.8 vs. Vivitar Series 1 135/2.3. 
Somehow, all my collected comments on the Pentax have been erased. The 
comments I've collected about the Vivitar state that it's sharp at all 
apertures. The Pentax, as I recall, must be stopped down a bit to become 
truly sharp. Not surprising, since it's about two-thirds stop faster but 
only 5mm wider in filter size. I was drawing an inference that it "can't" 
be sharper than the Vivitar.

I also agree with you that the lack of an autodiaphragm can be a big drawback.

Paul Franklin Stregevsky
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