Re: [photo-3d] Re: Medium Format viewer

["Don Lopp" <dlopp@xxxxxxxxxxxxxxx>]

Mr alan Lewis stated that viewer lenses are "the bigger in diameter the
better " but my experience is to the contrary and that bigger is a cheap
substitute for having control of the interocular spacing - pass  a 35 mm
viewer around and watch the different viewers make interocular adjustments-
when available which is a given with most 35 mm viewers. DON
----- Original Message -----
From: "Alan Lewis" <3-d@xxxxxxxx>
To: "photo-3d@xxxxxxxxxxx" <photo-3d@xxxxxxxxxxx>
Sent: Wednesday, January 17, 2001 4:39 AM
Subject: [photo-3d] Re: Medium Format viewer


> > >Don, if you are listening, what was the lens focal
> > >length of that viewer?  65mm?
> >
> > Wow! That should give a really BIG image... does that add a
> > lot of distortion?
> > Does a lens with a different focal lenght than the "normal"
> > changes anything in the perceived depth of the stereo
> > image???
>
> Choosing the viewer lens to use is a tradeoff.  I have found that it is
> almost impossible to find one lens that will accomplish everything one
> wishes for.
>
> A medium format viewer could use a lens of approx. 60 to 65mm and still
> cover the full image, but I have not yet found a lens that will do this
> distortion free.
> I think Don's viewer lens is even shorter than this.  What happens as
> you go to a shorter f.l. viewer lens (beside the perspective change
> George mentioned) is that you go towards the full circle type of image,
> without the mount window being in the image.  Distortions can increase
> if you use a large diameter lens that is necessary for medium format
> viewers. But the distortions may not be objectionable because you feel
> so immersed in the image and you no longer have a well defined window in
> the mount to judge the type of distortion you are getting.  It probably
> just amounts to a sharpness judgement from image edge to image edge.
>
> My personal preferences are that the medium format image (or any stereo
> image) must be sharp from image edge to edge (corner to corner).  That
> is my first criteria.  Second is the image coverage of the lens.  The
> bigger in dia. the better. Third is the pincushion or barrel distortion
> judgement (it's always a judgement). Fourth is the focal length.  I try
> to stay with an ortho lens arrangement for my camera/viewer (75-80mm
> f.l.).  This is as much for practical reasons as for perspective
> reasons.  Practically speaking I have found that any lens less than 75mm
> suffers too much from some of the conditions that I have mentioned
> above.
>
> But I continue to try any and all lens spec's in my medium format viewer
> that I can get my hands on.  The experimenting is enjoyably, and so
> educational.  Nothing beats actually trying something rather than
> following what others' say is right or wrong.
>
> --
> Alan Lewis
> mailto:3-d@xxxxxxxx
> http://members.home.net/3-d
> Serious viewers for Serious viewer's
> New stereo viewers & Stereo Wedding Photography
>
>
>
>


 

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