>> Ken, I was not under the impression that *any* of the OM lenses
>> contained aspherical elements, much as this has been speculated before
>> on some of the better ones. What information do you base this on?
>
> I suspect Ken "tripped over his own tongue" as the words poured out on to
> the keyboard, moving from OM specific toward
> modern lens design in general without pausing for "breath" (or
> clarification).
Well, maybe. Sometimes, I'm typing this junk out on the iPad.
I will clarify one thing regarding correction and aspherical elements.
Aspherical elements are but just one technology available to perform
correction. Depending on what the element is doing, a single
aspherical element can replace up to five normal elements in some
cases. But, let's consider the Zuiko 90/2.
Officially, this lens contains no aspherical elements. While this is
likely true, Olympus has been known to use technologies and not
bragged about it either. What this lens most certainly has is a
floating elements and extensive focus aberration correction. In a more
modern lens, this would be usually be done with the addition of an
aspherical element or two.
Aspherical elements take on a few forms. What I am referring to are
the shaped lens elements which do not have a uniform curve on a given
surface. The shape of the element is optimized to correct for a given
focal lengh or focus distance. Sometimes even an aperture. When the
photographer adjusts away from the ideal position the aspherical
element will start to render oddities into the the defocused regions
of the image.
One lens which is mind-boggling is the 35-80/2.8. This this is a
variant of the triplet, but with some interesting twists. 16 elements
in that lens and more lens groups shuffling around during a zoom than
you can shake a stick at. The level of correction in this lens is very
high, but it took six expensive pieces of glass inside to do it. A
couple of aspherical elements would have probably eliminated half the
glass in this lens.
Who knows what they would have done to the amazing bokeh of this lens, though.
As said before, I'm surprised that Olympus engineered four distinctly
unique general-purpose lenses in nearly the same focal length. The
final two, the 100/2 and 90/2 being so close, yet so far. It's like a
challenge went out to two teams of lens engineers to build the best
short-telephoto they could. Working separately from each other the
90/2 and 100/2 resulted. Both were so good that Olympus just decided
to build both.
That's my story and I'm sticking with it. I can't come up with any
other theories that make sense.
BTW, anybody else ever notice that several of the descriptions in the
esif look a lot like Khen's verbage? Read the 80/4 characteristics.
AG (epoch-making) Schnozz
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