P3D Re: Viewer Lemons

[Eric Goldstein <egoldste@xxxxxx>]

Brenda Nowlan wrote:

> What about the actual glass?  I have known photographers to "test"
> various lenses within the same brand and focal length.  I have even seen
> articles in photo mags addressing lens testing.  You test sharpness of
> lenses on Realists.  Does every Realist with David White lenses test at
> the exact same sharpness or distortion?  Does every Realist with Ektar
> or Ilex Paragon lenses test at the exact same sharpness or distortion?
> I thought with all the testing that is talked about, the implication to
> me is there can be some variation.  Am I misunderstanding this?


Brenda is both a careful reader and a quick study. Yes, with pre-late
60s/early 70s optics, there can be significant individual variation
between examples of the same system. Before then, even consecutively
serial numbered lenses from top end manufacturers such as Zeiss and
Leitz can vary measurably and visibly. Ektars differ, Ilexs differ,
David Whites differ. I've seen Realist Custom "Rare Earth" lenses (a
bunch of marketing bunk, BTW, and the glass on Kodaks is probably better
grade than on Customs!) which were visibly marginal/indifferent
performers. Many old timers believe that when you look for a used
camera, you might want to consider that the most beat-up old users got
that way because they have the best lenses, while the clean cameras went
either untested or unused because the pictures weren't so good...

Camera lenses do vary on our classic cameras, even between the left and
right lens on your stereo camera! Viewer lenses will vary as well. One
significant area of lens variation with viewers is contrast... different
RBs all seem to have different degrees of hazing. Interestingly, the
Green Buttons and achromatic HandyViewers I've seen seem to have higher
lens contrast than RBs, perhaps because they are newer? I have found the
field flatness of Kodaslide II viewers to vary visible between examples.
I have found the centering of many viewer lenses to vary a bit.

But I think Dr. T's point is that lens variation tends to be less
significant with viewers from the same manufacturer than cameras from
the same manufacturer, because they are simpler optical systems and so
there tends to be less variation. Kingslake discusses that triplets are
not the easiest lens systems to fabricate, and small differences in
glass, grinding, and fitting can make for varied optical performance in
the camera. This is especially true for the front cell focusers.
Achromatic doublets in viewers less critical, so less variation.


Eric G.


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