[photo-3d] Re: Stereo Binocular photographs?

[<donaldparks@xxxxxxxxxx>]

> P.J.Homer wrote:

> I have just recieved a pair of those compact none prismatic binoculars
> They actualy seem to be quite good quality and I am
> more pleased with them.  I have found that they fit nicely over the lenses of
> my Fed camera although they need a little support to ensure they dont drop
> off. I have already tried using some frosted tape as a diffuser in the film
> plane and the images fill the
> frames and seem to be sharp once focussed. The cameras own distance
> settings dont seem to make much difference, should focussing the binoculars
> visualy before slipping them over the camera lenses do the trick? I realise
> that for the distant objects viewed with the binoculars the stereo-base
> will be rather small especialy as these type of binoculars do not increase
> the base slightly as prismatic ones do except for the modern trend which is
> to have the objectives closer than the eyepieces. At least these will have
> a bigger stereo base than that type and the image viewed through them is
> stereo even a little cardboard as binocular views tend to be. They also
> give an interesting distorted stereo view with great depth of field
> allowing for close ups if viewd through backwards but the image is small,
> especialy on the film plane. I have actualy meant to get a pair of these
> for some time because you can get an adaptor for them which turns them into
> a compact stereo microscope.

     Yes, you can take stereo slides through a pair of binoculars.  Years ago I
made an adapter to mount a pair of wide angle 7x35 prismatic binoculars in front
of my f 2.8 Realist.  I found that a wide angle type binocular has large enough
prisms to yield the wide field of view  to provide full coverage for the 5p
Realist size film images.  The corners are not cut off and slides can be
reasonably sharp to the corners.

    To focus I had to calibrate the binocular's focus wheel.  On that particular
binocular the focus wheel was fairly large diameter with polished aluminum
segments around its circumference.  There was enough room on each segment
surface to write the distance value that corresponded to that segment's focus
distance.  I set up a tripod to hold the camera + binocular rig with the back
off the camera and a ground glass taped to the film plane.  I left the Realist
camera focus set to infinity and put a dark cloth over me so I could see the
image focus on the ground glass.  I turned the binocular focus wheel to get a
sharp focus on the ground glass and recorded the distance to the object that was
in focus at that setting.

    I used the binocular setup to take pictures of birds, animals and sports
action that you usually can't get close to.  The main problem was in determining
an accurate distance from me to the subject.  I couldn't guess values as
accurately as I needed.  I bought a range finder that had about a 10 inch base
to read these distances so I could then set the binocular focus for taking the
stereo slide.  I calculated the combined rig aperture at
f 8. With the old ASA 25 Kodachrome I usually had to use a tripod to get good
steady pictures.  With faster film I could hand hold some shots at 1/200 sec.

    It was easy to aim the rig.  I could look through the center viewfinder of
the Realist camera and sight down the center axis of the binocular.  The
geometry of that particular binocular had a clear line of sight down the center
and I mounted a small window on one of the binocular cross links to sight
through.

    I had a lot of fun experimenting with taking telephoto stereo this way and
got a few pretty nice pictures.  With the prisms displacing the sight lines the
base separation was about 5 inches.  This gave a reasonable amount of depth if
the subjects weren't too far away.  I was really disappointed when I had a
burglary and one of the things taken was my calibrated pair of binoculars.  I
have started making and calibrating another binocular telephoto rig but haven't
had time to complete and test it yet.

Regards,  Don

Dr. Donald J. Parks
Mechanical Engineering Dept.
Boise State University