[MF3D.FORUM:300] Re: New addition to MF viewer gallery

[Tloc54452@xxxxxxx]

In a message dated 2000/03/18 14:35:26, bglick@xxxxxxxx writes:

>1.  Taking stereo shots requires lenses that are identical fl's.  I have
>read that slight differences in fl can alter the stereo effect.  Does this
>mean lens of different fl, such as 80 and 78mm, or can it also mean the
>tiny
>differences between two 80mm lenses from the same maker.  Although they
>would be very close, they can still vary slightly... the book did not
>identify how tight lens tolerances need to be.

I think this matching of lenses is a bit over done in a sense.  When you
go to the optometrist and he slaps some new glasses on you, you run
into a much bigger mismatch than this.  So in a viewer, where the lenses
are just aids for your glasses, I'm not sure I'd worry too much.  The 
mismatch wouldn't be too important in a camera either except that
when you paste the film clips in mounts, the holes on both sides of the
mount are as precisely the same size as the manufacturer can make 
them.  So if you use two different focal length lenses on the camera,
you will have mismatches at the edges of the apertures unless you
have custom apertures to match the focal lengths.

>2.  My new 6x6 stereo mounts from RMM has one side of image area larger
>than
>the other.  Does the larger window side mount closest to the viewer lens
>or
>does the smaller window side mount closer to the viewer lens?

Smaller, else you would see both sets of edges under some circumstances,
in theory.

>3.  What type of tape is used to tape the mount closed.  I noticed on some
>mounts are taped closed by a silver type tape.... what is this, and is
>it
>necessary?  If so, where is it purchased?

Silver tape is good for the heat of projection.  Reel 3D probably still
sells it.  It's really opaque so it's good for masking.  Personally, I use
the Weiss tape in paper mounts and then glue the mounts shut for
extra stiffness.  I doubt anyone else does it but it's easy to do and
gives a good result, unless you ever want to remount!

>4.  Stereo cameras with fixed lens positions are quite popular.  However,
>based on the formula  (1/30) for determining proper lens spacing based
>on
>subject distance, it seems stereo cameras with 65mm spacing are best
>utilized for shooting close subjects.  If you are shooting subjects 20
>feet
>away, it is better to use a dual camera rig in which the lens spacing is
>further apart to as per the forumula.  This of course leaves out the
>variable of both shutters firing simultaneously, which is a photographic
>consideration based on movement.  My question is, is this completly right?
>If so, I imagine a dual camera rig on a slide bar with dual cable releases
>would be the best all around option for shooting a wider variety of
>landscape scenes vs. a fixed stereo camera.  Right?  Were these fixed stereo
>camera primarily made for protrait shooting?

The 1 in 30 formula would be to maximize stereo effect.  Generally,
you'll be happier if the lens spacing matches your personal interocular.
Then everything comes out life size.  If you double the camera lens
spacing, you get the view of a giant whose eyes are twice as far apart
as yours: everything looks tiny.  If you shoot a pair with half your
IPD, you get the gnome's view: everything looks twice as big.  Of
course rescaling like this can be a lot of fun, if that's what you want
to do.

If you want to see depth far away, you'll need large spacing, but things
will look tiny - so a 20' bar will do good fireworks but the fireworks
will look miniature.  Make sense?

You have to decrease spacing if you have miniature stuff or you will
have frames with nothing in common.  So here you make things look
bigger.  When my son was little, he had "action figures" like the rest
of the little guys.  I took pictures of them with the camera spacing
(on slide bar) to match their scaled-down height so that when my
son viewed them, they looked full size.  That was interesting.

John B