On Thu, 14 May 1998, gma wrote:
|
|
|John A. Prosper wrote:
|
|> On Wed, 13 May 1998, gma wrote:
|>
|> |On a different topic, I took a look at the mp-zuiko-tests page on your
|> |site last nite. I was quite surprised at one of the conclusions I drew
|> |from the data: that the Zuiko zooms are every bit as good as the primes
|> |(if not better!) I base this mainly on a comparison of the resolution
|> |test numbers. For example, the 35-105 at 105 appears to be
|> |substantially better than the 100 F/2.8 and even the 100 F/2.0 !! And
|> |the 35-70 F/3.6 at 35 betters the 35 F/2.0.
|> |
|> |There are counterexamples, but my point is that I'm surprised the zooms
|> |are even close to the primes and astonished that the #s in many cases
|> |are better. Do you (or anyone else) have any thoughts on this? Or is
|> |my interpretation of the data faulty?
|>
|> One thing to keep in mind is that the relatively lower
|> contrast of zooms, caused by their higher lens element
|> count, will always cause them to be lesser in sharpness to a
|> fixed lens built to similar design standards.
|
|John;
|
|I think you're stating here what I assumed would be true, that fixed would
|be sharper than zoom, all else equal. But the data in the mp tests on
|Lees' page seems to contradict that somewhat.
Then suspect strongly that all else is NOT equal. :-) For
instance, the 35-80/2.8 uses a UD element and 5 refractive
index lenses. A fixed lens may employ less exotic material
which compromises sharpness (and contrast) below that of a
pro zoom even though it uses a lower element count.
Furthermore, I have been told there are as many as 200
different types of glass used in lens manufacturing.
(Others may have a more exact figure.) The manufacturers
tend to choose the various grades of glass with respect to
either economic or performance (or somewhere in-between)
constraints. I also suspect the definition of what
constitutes UD glass has evolved over time. For example,
the 180/2.8 lens used to be considered a lens with exotic
glass: it seems it is not treated that way anymore.
Therefore, you may want to compare modern (1980+) zooms
against modern fixed lenses to have a certain degree of
confidence that you are comparing apples with apples.
|I've always blindly bought primes for the very reason you've stated. But
|after seeing the numbers, perhaps a couple of the Zuiko zooms would give
|results of equal caliber?
|
|One reason I'm asking is that I've found a guy who's got 4 or 5 Zuiko zooms
|he's going to be selling and I'm wondering if I should pick up a couple.
|I'm thinking specifically of the 24-28 and the 35-105.
You may want to gibe Gary Schloss a shout here. I believe
he has experience with the 28-48/4. Several posters can
offer their testimonies on the 35-105. I haven't used any
of them.
All I am advising is that you match modern zooms (e.g.,
35-70/3.6, 35-80/2.8) against their fixed counterparts of
similar design (in this case, pro) construction (e.g., the
latest incarnation of the 50/1.2, 90/2, 100/2). I think the
24-48/4 was a pre-1980 design, and the 35-105 is definitely
modern.
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