[MF3D.FORUM:557] Re: Solution

["Bill Glickman" <bglick@xxxxxxxx>]

Tom

       The first test I performed was a grid test.  I shot a full frame grid
with each lens without moving the camera, then laid the chrome on top of
each other... the grids were almost perfectly aligned, the difference was
about .07mm on top and bottom horizontal lines.  The vertical grids were
perfectly aligned.

       Then I took stereo shots on a slide bar, the first shot with lens
one, then switched cameras /lens and placed it 65mm away for perfect stereo
placement.  So in essence I used the same set up, two cameras, two lenses,
but not shot simultaneously.  Those chromes mount and view perfect.
However, what fails is when I shoot with the cameras side by side, with the
inter lens spacing at almost 6", (the closest I can get them) and then I can
not mount and view without the double edge problem.  (Of course the scene
called for much closer stereo base)

         Doesn't this conclude that I am simply violating the stereo base
because I am not being able to bring the cameras close enough together.
John B's formula in these examples called for a close base, under
70mm....Since I am way further apart, I can only get the center of the
images to fuse...  It seems I can not overcome the violation of the stereo
base by mounting differently?

Unless I do what Paul suggested, crop away the sides and make a smaller
image to view, then it would work fine, but it would also turn MF stereo
into 35mm stereo... and that is not my goal.  Your comments please...

Regards
Bill G


> >I also see double imaging towards the edges in a gradual way.
>
> If the comment above is accurate, then it one of two things is the
> culprit. Either your lenses are optically different in some way, or
> your camera bodies are.  The gradual double image is a problem of
> geometry, not of mounting.
>
> Check that both cameras are in good shape.  Pay particular attention
> the lens mounting and film plane, which will affect the camera's
> geometry.
>
> You can solve this once and for all for the cost of a single roll of
> film.  Take the following test shots with a single camera on a slide
> bar.  I guarantee the results will be conclusive.
>
> 1. Put the camera on a tripod.  Take an ordinary photo with one lens,
> then take exactly the same photo with the other lens, no camera
> movement at all.  This will compare the lens geometry while keeping
> the camera body the same.
>
> The chromes *should* look identical if you sandwich them together on
> the light table.  But the lenses may have different pincushion or
> other distortion.   Maybe one was repaired incorrectly, or
> reassembled incorrectly.
>
> 2. Simulate your twin rig with the slide bar.  Shoot with lens A,
> slide the camera five inches, and shoot with lens B.  (Again, with
> the same camera.)  This will test the theory that your slides have
> too much depth.  Try one or all of the MAOFD configurations below:
>
> a. Shoot a scene where the nearest thing is 20 feet away, and the
> farthest thing is at infinity.
>
> b. Shoot a scene where the nearest thing is 12 feet away, and the
> farthest thing is 30 feet.
>
> c. Shoot a scene where the nearest thing is 8 feet away, and the
> farthest thing is 21 feet.
>
> If test #1 makes identical images, and test #2 makes mountable and
> viewable slides, then your camera bodies are geometrically different
> in some way.  I'm betting your lenses will fail test #1.
>
> Best Wishes,
>
> Tom
> ---
> tmd@xxxxxxxxxxx    http://www.deering.org
>