Dennis's wide angle optics (Re: MF Expo)

[Greg Erker <erker@xxxxxxxxxxxxxx>]

> Greg,
> The lens wasn't designed from the ground up. Two dublets were mounted in a
>barrel in what is called a symetrical arrangement.The two dublets were
>chosen from a stock assortment by some guy in cherry hill NJ--I forget his
>name. Supposedly it is better than just a single doublet.I guess its
>possible to engineer the optimum lens and have them ground and cemented but
>it would be quite expensive. It would be nice to talk to a real optics
>engineer and find out what the state of the art is capable of.
> You dont see any real wide eyepoint lenses.I guess there are limitations
>on wideness of apparent view without distortion.

  Is this a double (cemented) achromat system?
(Similar to the double 36x94mm achromats Alan
Lewis and I are using to view full frame 35mm).

  Or is a doublet an airspaced achromat? (Not
totally up on my terminology).

  Getting a wide angle AND large diameter
viewer lens is optically difficult (I hear).
Usually you are limited to f2 or smaller (ie
80mm FL by 40mm diameter or the Red Button
44mm FL by 20mm diameter). To get past that
you have to go to more elements and the symetrical
one ofter works well.

  Alan's and my 50mm FL by 36mm diameter double
achromat works out to be f1.4.

Greg