On Mon, 9 Jul 2001 23:18:44 +0200, you wrote:
>It is not a bad lens - there simply are better ones.
Please name these "better" 300mm f4 or f4.5 lenses. If
they are better than the Pentax 300/4.5, they are very
good indeed, and I will certainly try them out.
I'm serious when I ask this question, because the list
of 300/f4 or f4.5 lenses in K-mount, either AF or
manual focus, is not a very long list, and I'm always
on the lookout for better lenses.
>I used to own
>one - its central definition and contrast is very good but edges are
>quite poor until you stop the lens down to about f/11 - which is not
>a good result for a lens that is relatively slow - by contemporary
>standards.
I don't consider F4.5 to be significantly slower than
F4. It is only one-third of an f-stop difference. I
doubt anyone wil miss any shots because they are
shooting at 1/350 instead of 1/500. Heck, with print
film, you can go ahead and treat it like an f4 lens.
The film latitude will make up for a third of a stop
shutter speed.
The f4.5 max aperture of the Pentax 300/4.5 trades a
bit of speed for a significant reduction in the size of
the front element, which, if nothing else, give the
impression of a smaller lens.
If the comparison is to a large and expensive 300/2.8,
yes, the 300/4.5 could be considered "slow." But in my
opinion the only reason to carry my 300/2.8 (which is
not hand-holdable, nor will it fit into an average
camera bag) is when I want to add a teleconvertor to
get out to 420mm or 600mm. If I only want a 300mm focal
length, the 300/2.8 stays home and out comes the
300/4.5.
> Wide open it also vignettes badly.
This is news to me. Mine doesn't vignette wide open.
Maybe a half-stop light fall-off in the corners when
shooting in difficult conditions, such as against a
clear blue sky, but almost every lens will show such
behavior until about f5.6 or f8.
>I would say it
>represents quality of good amateur lenses.
Huh? I don't understand this comparison. I have used
several lenses, primes and zooms, at 300mm, in Pentax
and other mounts. The Pentax 300/4.5 has significantly
better optics than any except perhaps the 300/2.8 at
f2.8.
It is also a significant improvement in optics and
ergonomics over some pretty good Pentax lenses I've
owned, including the SMCP-K 200/2.5 and SMCP-M* 300/4.
The Sigma 400/5.6 APO Macro, which is in the smae price
range, is a pretty good lens, but no better at f5.6
than the Pentax 300/4.5 at f4.5.
As for really "amateur" lenses I've used, like a Sigma
something-to-300/f5.6 and Canon 75-300 IS USM, well,
the Pentax easily outperforms them at any aperture.
> Lack of a tripod mount is
>a drawback
I used to think the lack of a tripod mount was a
significant drawback, but lately I've changed my mind,
at least about this Pentax lens.There's space at the
aperture ring and at the front end where you can
support it with the left hand.
If one wants a tripod mount, the F* 300/4.5 has a huge
one, which is plenty big enough to be a pistol grip
also. The F* 300/4.5 is also able to use the much
smaller tripod mount from the A* 200/4 Macro.
Thate's not too many 300mm primes in Pentax AF mount.
There's the Pentax F* and FA* 300/4.5, the much more
expensive Pentax FA* 300/2.8, the Sigma 300/4 APO
Macro. Any of these lenses would be a good choice.
I don't believe there are any lenses in Pentax AF mount
that will give the the excellent optical performance at
f4.5 of the Pentax F* or FA* 300/4.5. But I'll keep an
open mind if someone wants to prove me wrong. I can
always go to the local shop and try out a lens for
myself.
--
Happy Trails,
Texdance
http://members.fortunecity.com/texdance
http://members1.clubphoto.com/john8202
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