You will be loosing automatic aperture, which can be a pain or not. It
was for me, but then, I shot them mostly wide open. I would advise the
same, as it's a PITA to close the lenses manually before shooting (at
least the 180 has a pre-set aperture, which works better than the 200)
180 is great lens, but due its age, it can have lower contrast (it
also needs a really big lenshood), until f/4.5-5.6. Details are still
very well rendered, but the maximum black rendered is lighter. Depends
on light and lenshood a bit, and stopping down helps. It's big and
heavy. This lens is great even on Pentax 67, without any problems. It
does have a very nice and pleasing character, making me use it time to
time on a DSLR even if I have a good 80-200/2.8 zoom. Do get the MC
version, though. It's a Sonnar design, derived from Tessar, something
that can still hold its own pretty well (Leitz Elmarit 2.8/50, as well
as Voigtlander Cosina 3.5/50 Heliar, all counted among the best lenses
ever, are derived from Tessar designs)
200 is said to be even better, it is an gaussian design, Biotar in
fact. That is, it bears similarities to Planars of Western Zeiss. It's
supposed to be very good as well, but I never tried the lens myself
with film in camera.
Both of the lenses are true longfocus lenses, not telephotos. That
means that they are actually _faster_ at closest focus than a
telephoto of the same 2.8 aperture. The 180 also has some of the
nicest character I have seen. The fact that it covers much larger
image circle means there is little vignetting. However, they ain't no
SMC. But their low element count offsets that a little, as there
aren't so many reflections as in a big telephoto. However, their large
front elements do need a long lenshood. Otherwise, overall lowering of
maximum black will occur. Carl Zeiss Jena's multicoating ("MC" mark)
is pretty good, but not up to SMC or similar.
If you are interested, I can send you a file from my 6MP DSLR shot
with the 2.8/180 Sonnar.
Best regards,
Frantisek Vlcek
