P3D Re: Lme Kbee super wide angle

[Oliver Dean <3d-image@xxxxxxxxxxxxxx>]

Hi, Linc!

Lme Kbee wrote:
> 
> I just got a medium format camera and a 30mm lens for
> it.  For medium format, that 30mm is a full frame fish
> eye lens.  So, what I was wondering is, if I am able
> to track down some maching lenses (30mm) to view some
> slide bar stereos taken with that set up, how will
> that look different than with the 78mm lenses of the
> saturn slide viewer?

Forgive a hasty answer:  You probably won't be able to find achromat
viewer lenses capable of covering medium format (2 1/4' x 2 1/4") at
only 30 mm focal length for anything less than a fortune, if at all. 
Viewer lenses have different requirements from camera lenses, because
the image being viewed is a virtual image rather than a real image, and
is, therefore, subject to having the view of the corners severly cut off
if the lens diameter is not large enough.  Viewing a medium format image
with a 30 mm focal length lens would require a lens diameter much larger
than the focal length in order to see all corners of the image, which
means a maximum lens aperture of less than f/1.0, and such lenses are
difficult and expensive to design.

Since the fisheye lens is a sort of special effect lens anyway, I
suggest viewing such pictures in a normal medium format viewer and being
happy with the additional distortions.  Perhaps some others on the list
who are more conversant with optics could suggest some alternatives with
compound lenses, but I think that the coverage enabling you to see the
whole image would still be a problem with a 30 mm effective focal
length, no matter how it is obtained.

Cordially,
Oliver Dean