At 09:07 AM 5/7/2003 +0100, you wrote:
Hi,
> The 75-150 is a gentle little lens which seems to do nothing badly.
Yes, mine's been sitting in the cupboard unused for several years, but
I've been playing around with it again recently. Took a couple of shots
to compare it to the 90mm/f2 and I'm very curious. One thing I noticed
really quickly is that the colour rendition seems far less punchy. I was
looking at a red brick wall with a tree in front of it, both lit by a low
sun, with a great blue sky behind it. The 90mm/f2 being the impressionist
it is, gave a Velvia look, whereas the 75-150 was a bit pale.
I noted this somewhat in C.H.'s photos too. The 75-150 seemed to have
marginally the lowest contrast of all his photos with the D60. The lens
has a reputation for being the least sharp and least contrasty at the long
end.
I thought C.H.'s example acquitted itself very well though. Absolutely
nothing shabby about it.
There must be huge sample variation with this lens, not the least because
of its sheer age. My example I had always thought was pretty good. I had
a little repair done to loosen up focusing and we discovered it had fungus
on one element (I hope from a previous life -- I picked it up in a pawn
shop). It is much sharper now! There are supposedly lots of examples of
the older 75-150's with element separation. That will spoil contrast too!
It's quite possible to make a lens with a large number of blades that has
bad bokeh. Usually, the blades are a bit rounded off, to make the
diaphragm a bit more round. Straight blades would give regular
octangles. Rounding the blades in the other direction would give stars :-)
The key article on bokeh that was referenced recently shows an example with
triangles. I interpreted that to mean that you can get some really weird
artifacts from unusual diaphragms, not that the diaphragm itself is the
sole cause of good or bad bokeh. Or at least that's what I'm saying now
that C.H. has sort of demonstrated that the blur characteristics must be
more due to the lens formulation than a raw count of aperture blades. :^)
Joel W.
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