Re: TECH-3D digest 210

[T3D Eric Goldstein <egoldste@xxxxxx>]

Bob H writes...

> The gist of the arguement which can apply to any 
> lens not just classic or computer designed, is that all the 
> abberations are not eliminated and how the designer chooses to treat 
> what remains govers the "flavor" which is what the Japanese use when 
> translanted.

I believe the Japanese word for it is "bokeh (sp?)" or something
similar.

This leads into a fascinating area of sensory recording systems... all
of which do in fact have artifacts and distortions, some more "pleasing"
than others. The trick is in discovering which ones we "like" and how to
design to achieve/control them. German classic lenses such as the
Planar, Xenotar and Sonnar are often described as possessing the curious
characteristics of "smooth, yet sharp" image quality greatly flattering
to skin tones. Other classic lenses are said to possess a plastic, round
or dimensional quality which is often attributed to a certain amount of
residual curvature of field, and which Leitz and Zeiss are said to
retain to this day in the summicron and planar (retrofocus a la
hasselblad, not rolleiflex)

I'll add a quick comment with regard to the character of the out of
focus areas of different lenses, which is one area for which the Germans
are always given higher praise than the Japanese for reasons ineffible
and unctuous. This character often includes but is not confined to the
shape and contrast of the blurred image, and according to one chap I
spoke with, how in focus or out of focus it is! Ken Ruth, himself an
accomplished and exhibited photographer and well known classic camera
technician, told me not long ago that two lenses with identical focal
lengths can have different DOF at the same aperture. He says that old
view camera lenses were notorious for lens designs which featured longer
image cones with notably greater DOF but less overall sharpness (thus
the image never truly "focused").

I am not an engineer and alas one of Paul Boyers creative types destined
never to be accomplished in both technical and non-technical arenas; I
do not possess enough knowledge to evaluate the physical plausibility of
any of this so take what I (and others) write with a grain of salt...


Eric G.


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End of TECH-3D Digest 211
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