Re: 35mm Slide Viewer

[P3D John Bercovitz <bercov@xxxxxxxxxxx>]

Sang K Chung writes:

> They are too narrow (viewing angle) for my liking.  I have
> constructed my own 35mm slide viewer but without 100% success.
> It still gives far more distortion (pincushion) and lacks
> clarity.  I have recently gone into medium format for this
> reason.  Are there anybody who have successfully constructed a
> 35mm slide viewer that provides wide angle (at least 120 degree)
> as well as clarity and low distortions?

Because of scale factors, it is very difficult to make short 
(in absolute terms) focal length lenses which are wide angle 
and free of aberrations (such as distortion).  That's one 
reason why people move up to medium format when they want wide 
angle.  Another reason is that as you go to a wider angle, the 
focal length decreases, and you get closer to the film (all 
desirable) but then you can see the film's grain (undesirable).  
So again, you turn to medium format where you don't have to get 
so close to the film to have wide angle.

Don Lopp's medium-format wide-angle viewer was mentioned in 
earlier posts.  It is truly astounding.  It really gives the 
feeling of immersion.  I don't know how he found such short 
(= wide angle) lenses the are so free of aberrations.  I'd 
like to know if there are more of those lenses and if we all 
can have a pair.  Mike, do you know?  8-)

Even Don's viewer is only about 60 degrees and you want 120 
degrees.  For you I would recommend a lensless viewer since 
lenses are the limitation.  A Wheatstone mirror viewer will
do the job.  You will need to print very large transparencies 
if you want to go this way. This is not hard if you go to a
pro shop for the transparencies.  If you can view at a distance 
of 16" (400 mm) then you'll need a 55" diagonal for your format.  
Assuming the format has a 4x5's aspect ratio, this would be a 
transparency which is 34' x 43".  Don't laugh; it's do-able.
All depends on how bad you want it.  8-)

There's also the LEEP viewer but that's another, very sad, story.

John B


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