T3D Re: T3D Re: T3D Re: T3D Now yer in trouble

[erker@xxxxxxxxxxxxxx (Greg Erker)]

>I guess most people on this list would be
>interested in 35 mm format.  MF is easy
>and large format even easier.  V-M is
>difficult but not too difficult because
>of the smaller field of view.  So I would
>guess people would be most interested in
>35.  I would think ortho.  If not ortho,
>again, the design is not that difficult -
>a cemented doublet would do.  But I think
>the decision as to which lens is most
>wanted should be up to the group so I
>left that blank.

  Ortho for Realist and Kodak cameras is
35 mm FL. Ortho for Belplasca and Fed is
37 mm (I think).

  Do we pick 36 mm FL as a compromise or
go to 37 or 38 to make the design a bit
easier?


>What would you like?  I would personally
>like a lens of large enough diameter that
>no adjustment is necessay but the cost could
>be exorbitant.

  How large diameter do we need to cover
the spread :)


>I would think this would be a many-lens design
>and so would cost like a good telescope eyepiece
>or ~$100 each, $200/pair.  Is this too scary?

  Kinda high for me. The dual Surplus Shack
achromats cost from $22 a set to $32 a set
depending on quantity. But you need to make
a lens holder. Pluses are the large diameter
(36mm) and price. Minuses are the 50 mm FL and
pincushion distortion.

  The next step up might be the 6x Edmund
magnifier that Eric G has. This works out
to a FL of 41.7 mm. It is coated and made
from dual achromats and would cost $160 per
pair (less if we had a group order). Pluses
are: closer to ortho FL, sharp to the corners
(according to Eric) and lenses come in a
focusing mount that could potentially be
used in a viewer (individual eye focusing).

  This proposed design would have to come
in a holder if it's a many-lens design.
(I assume. Unless it's a cemented triplet.)
It would have a bit higher magnification
than the Edmund loupes and be somewhat
higher in cost also.

  Higher still, would be the Peak Aspheric
Loupe, sold by B&H for about $229 each
(AFAIR). 7x and full frame coverage is
claimed.  This works out to a FL of 35.7 mm
if they are using the 250/FL method and
not the 1+250/FL method.

---
  So if we are talking $200 or more a set
the question is what we gain over the Edmund
and Peak loupes?

Not trying to kill the idea, just asking - Greg E.



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