I tripped across a manual focus lens last night that I was not
previously aware of: The Tamron SP 300mm f5.6 Flat Field (model 54B),
an Adaptall2 lens. The two big things it has going for it are
lightness and close focusing capabilities.
The 54B is surprisingly light at 610 grams. For comparison, the new
DA* 300mm f/4 weighs 1070 grams. By my calculations, that makes the
54B a full POUND lighter. As far as close focusing capabilities go,
the 54B can match the DA* 300mm f/4 at 1400mm. ("With a 1.4m close
focus, the DA* 300mm is one of the closest focusing 300mm primes on
the market, in comparison, the Nikon and Canon 300mm f/4 focus at
almost 1.5m.) The 54B can, by itself do a 1:3.3 magnification ratio.
Put a Tamron Flat Field 2x on it, and you can do 1:1.6 (albeit at
f/11). Being able to get those kind of magnifcation ratios at 1400mm
makes it a potentially great lens for dragonflies, butterflies, etc.
All of that means nothing if the lens doesn't produce results with
today's DSLR. Looking at what people have done with it got me pretty
excited:
https://www.flickr.com/search?text=Tamron+54B
Check out this set by one user:
https://www.flickr.com/photos/slar/sets/72157630155808874/
I think there is a reason that this lens earns a very respectable 8.75
user rating in the Pentax Forums lens database.
http://www.pentaxforums.com/userreviews/tamron-adaptall-2-300mm-f-5-6-54b.html
Best of all, the one I found was $79 shipped. I love bang for the
buck! The general consensus is that this lens is optically the best of
all the manual focus 300mm lenses out there. One reviewer who has
tried a lot of them says: "SUPERB!! I guess don't need to say more. I
didn't find any weakness of this lens, color, sharpness, macro
capability just excellent, if compare all this features with other 300
mm lens this is the number one. Better than Carl Zeiss Jena Sonnar
300mm f/4, Pentacon/Meyer Orestegor 300mm f/4 , Nikkor 300mm f/4.5 AI
or Tair 3S."
The reduced speed of this lens (f/5.6 maximum aperture) is mitigated
by today's ability to get great results at higher ISOs. I thought I
would pass this along for anyone else who is looking for similar
capabilities without breaking the bank. Being an Adaptall lens, one
can use it with either a PK/M or PK/A adaptall mount (or an m42
adaptall mount, if you want to put it on your Spotmatic F. :)
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