Gary,
You have piqued my interest with your comment re the 40mm f2. Looking
it up in the "The OM System Lens Handbook" (C240E-1984), I find, not
clarification, but even more vague descriptions leading to confusion.
The way I, and I think likely, many others, visualize the glass material
would put it into maybe two types, regular and ED (fluorite is a
different story I guess). Your info below adds another type (either Low
Dispersion or Ultra Low Dispersion, take your pick). I then look in the
Lens Handbook and I start running into other types also, some of these
follow.
Low Diffusion (24mm Shift Lens)
Low Dispersion (40mm f2 , 1.4x Tele Conn. ,20mm f2 Macro) - description
identical in my book!
Special Low Dispersion (100mm f2 ,250mm f2 ,350mm f2 )
Partial Dispersion (100mm f2 ,250mm f2 ,300mm f4.5 ,350mm f2.8 )
Two Varieties of Flint Glass (1000mm f11)
*My Lens Handbook does not list the 180mm f2 or the 35mm - 80mm
f2.8
I guess my point is that the definitions seem to be not nearly so
clear cut as they are being stated in this and several other postings.
The glossary statement is just as Gary stated, but it does not address
which lens have or don't have it !
Is this some intuitive leap that I have stumbled along and missed the
jump off point? Am I fated to forever wander the elysian fields of
blissful ignorance, my 40mm f2 and I? Fated I ask, just on the basis of
semantics maybe and the lack of a definitive answer to my wandering plea
"Is it ED or not? Surely someone knows!"
Let's wait to upgrade the FAQ until we get, at least, a somewhat
consistent answer.
Rand E. ( who now knows quite a few more words that I did several hours
ago, just not how to use them in a sentence)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Gary Reese wrote:
>
> Giles writes:
>
> << These Zuikos have ED elements and I am sure there are others:
>
> 35-80/2.8
> 100/2
> 180/2
> 250/2
> 350/2 >>
>
> And, as mentioned, the 24mm Shift and 20mm f/2 Macro Zuiko, but not the
> 40mm f/2. The 40mm, as well as the 1.4x teleconverter have "low
> dispersion" glass, not extra low dispersion (ED). A look in the glossary
> of the Olympus OM System Lens Handbook reveals that Olympus considered
> what they call "ultra low dispersion glass" to be what we typically see
> as SLD or ED in today's marketing hype.
>
> The FAQ needs updating to include the 20mm.
>
> Gary Reese
> Las Vegas, NV
>
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