Jim Davis wrote:
> [someone wrote:]
> > Pentax invented multi-coating (although "invented" can have different
> > meanings depending on who, or who's marketing department, you are
> > talking to) . . . I don't claim expertise on FD equipment at all,
> > except in the case of this simple 50mm comparison.
Ok--there are early FD lenses with no coating designation; it may be safe to
assume that these have no coating or only a simple coating. Then, once the
designations started to appear (SC=Spectra Coating, SSC=Super Spectra Coating),
some lenses got the SC treatment, but most got the SSC treatment. After the
introduction of the "new" mount, imprinting the designations was dropped because
all but a very few lenses had a form of SSC coating; the 50/1.8, for example,
continued to get only the SC coating because, according to Canon, that was all
that was needed for that design. The coatings on EF lenses continue to be called
SSC, although there's probably no way to know what alterations and improvements
have been made to the process since c.1975.
I won't say anything about the optical quality of EF vs. FD lenses because this
discussion contains more heat than content, other than to suggest that to assume
that the newer lenses are optically inferior just because one doesn't happen to
care for the construction of those lenses is, um, ill-considered.
> I just want to add here that I bought a Minolta with 50mm 1.4 MC lens in 1970
> and it had multi-coatings on it.
As for coatings . . .
"1935:
Professor Alexander Smakula developed anti-reflex
layers for glass surfaces (Carl Zeiss T-coating) in the
Zeiss works. This coating, often regarded as the
optics´ breakthrough invention of the century, gives
the lens constructor completely new possibilities in
the development of multi-lens optics."
(source:
http://www.zeiss.de/de/photo/home_e.nsf/allBySubject/Launch+-+Zeiss-engl+JavaNavigator
)
Now, what constitutes "multi-coating" may be a matter of debate: Zeiss refers
here to "anti-reflex layers," not "an anti-reflex layer," and to this day refers
to the T* coating as a "coating" rather than "coatings" or "multi-coatings,"
although their (current) T* coating is a multi-layer process. FWIW I have a 1951
Rolleiflex with a T*-coated lens. I haven't been able to turn up any more
specific information than this (although I have seen photographs of Zeiss's
coating operation). I did find this interesting tidbit, although I make no
claims regarding its accuracy:
Subject: Re: [Leica] RE: Re: KINOPTIC lenses
From: Eric Welch <[EMAIL PROTECTED]>
Date: Thu, 10 Dec 1998 21:53:49 -0600
>Leica is moving towards true multicoating
They are not. Multicoating of all surfaces in a uniform manner is a
trick from the 60s, including Pentax, and is inferior to what you call
"staggered coating" and what Nikon calls NIC (Nikon Integrated
Coating) and what Zeiss does with T* coating. Leica, Zeiss and Nikon
can't be wrong. (I believe Canon too). Nobody making high performance
optics does the "uniform" Multicoating. The coating is part of the
overall lens formula. If all were coated the same, that wouldn't be
true.
Leica does it right now. Why would they go backwards?
Finally, somewhere recently, possibly as part of this thread, there were some
remarks regarding old designs vs. new ones. One thing that occurs to me is that
it doesn't really matter so much whether Canon was designing lenses using
computers back in 1975; what does matter is the quality of computer-aided design
at the time. As it happens, I was learning (not very well) to program in Fortran
using . . . punch cards fed into a card reader attached to a couple large
Burroughs 6800-series mainframes--not exactly an efficient way to work. One can
hardly argue that CAD implementations have not improved dramatically since 1975.
That said, it is interesting to note that Nikon has just announced a new 45/2.8
Ai-P lens that uses the classic Tessar design--four elements in three
groups--developed by the Zeiss company in . . . 1902. The point being, it isn't
the age of a design that matters, but rather its quality. Along similar lines,
the heft of a lens has no bearing on its optical performance. These are optical
instruments, not construction tools! I'm not a materials scientist so I don't
know anything about this one way or the other, but as a fairly rational person
it seems to me that it's entirely possible that non-metallic composite materials
could have distinct advantages over various metals for lens construction, in
terms of things like expansion/contraction due to temperature or resistance to
deformation. Perhaps it's irrelevant, but I notice that many EF lenses have a
built-in compensation for focus shifts due to temperature-induced expansion and
contraction; this seems like an advance to me, not compensation for some design
flaw. Just a thought. . . .
Here are a couple things some of you might find interesting:
http://www.mir.com.my/rb/photography/companies/nikon/hasselblad/lenses/hassel_lens_entry.htm
http://www.kkb.kz/~pws/ILYA/photo/contax/lenses/mtf/onlyzeis.htm
Cheers!
fcc
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