Doug Brewer wrote:
> Now, to the sentiment: Stratification
> of lenses aren't really a new
> concept. The K-mount Takumars are
> widely agreed to be "budget"
> efforts, with all the shortcomings
> attendant with the word, are they
> not? How long ago did they appear on
> the market?
You're correct, of course, although when I mentioned Takumar I
was thinking of an earlier time, when there was just the Takumar
lenses - i.e., before K-mount. I suppose the K-mount Taks came
out in the mid-seventies or so. I don't believe there were any
"budget" versions of earlier Takumar lenses. They were all
built to the same standard. And, while price "stratification" is
not new, it is, nonetheless, a relatively recent practice.
Further, I believe the K-mount Takumars were built to the same
quality standards as their SMCP brothers, and it was just the
absence of the SMC that was the main difference and allowed
Pentax to keep the prices down. IOW, the barrels, mounts,
helicoils, etc., were of the same quality throughout the lens
line. The Takumars didn't have plastic lens mounts, cheaper
built barrels, and the like, as we are now finding in
lower-priced lenses.
> Pentax, according to the info I've
> read, doesn't use plastic "elements"
> in their lenses. What they have done,
> in efforts to achieve Aspheric shapes,
> is to mould a =surface=, which is then
> cemented to a regular glass element.
I guess the semantics got in the way here. I realize that they
cement a plastic "shape" on to glass, but, in my mind, the two
are separate elements joined together to make a complete element
in the lens. IAC, however it's described, my concern is that
plastic is glued to glass.
> This is because, up to recently,
> the technology required to mould
> the optical glass to such a shape
> simply didn't exist, and forming
> the shapes with regular glass-forming
> methods would be too costly. Now the
> word is that the ability to mould glass
> to aspherical shapes is becoming more
> feasible, from both the technological
> and financial standpoints.
It's pretty well acknowledged that Leica used aspherical glass
elements in some of their early ASPH lenses. They were ground
glass, and as you said, quite expensive to make. IOW, the
technology was there early on to make such elements, or
surfaces, depending on the design of the lens. In fact, Leica
used two aspherical elements in (help me out here Rob) their
early ASPH 35mm Summilux. Yes, it's true that technology has
moved on, and that molded glass is now a greater possibility.
>
> What that means, of course, is continued
> stratification, but also the ability to
> build aspherical qualities into more
> consumer oriented lenses using the plastic
> surfaces, and including full-glass
> aspherical qualities in the higher
> ticket items.
All well and good, but my question and concern wasn't one of
marketing, but of quality. Sure, it's nice to know that
there's a $100.00 ASPH zoom lens out there for the "consumers,"
but it's as much marketing hype as anything else. Mr. and Mrs.
Average love high-tech buzz words, and ASPH sells. But are
plastic formed elements or surfaces of any long standing quality
and durability. That's not yet been addressed or answered. I
suspect that the quality isn't there, because if it were, why
not use these plastic pieces on the higher priced and
professional model lenses.
> As to whether the plastics used in
> lenses can stand the stress and
> strains, better ask a Canon shooter.
> I was told that the first Canon
> lens to incorporate a plastic element
> was the old FD-mount 50/1.8 that came
> out with the AE-1, and they have
> regularly used plastic elements since.
> That's a quarter of a century of plastic
> use, so a good lens repair tech could
> tell you if there have been any problems.
Red Herring time! <g> The question was not about plastic
elements, as we resolved, but of plastic pieces glued to glass,
call 'em surfaces, elements, or whatever.
--
Shel Belinkoff
mailto:[EMAIL PROTECTED]
"The difference between a good photograph
and a great photograph is subtleties."
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