[MF3D.FORUM:734] Re: I need a MF 3D Dr.

["Bill Glickman" <bglick@xxxxxxxx>]

Dear Fellow MF 3D ers

      Thank you all for your comments.... I have been obsessed with getting
this corrected before trip departure on Saturday, so after that, I will have
no more time to test.  I have thought about a lot of things and figured the
best way to proceed, was to do very comprehensive test that can
progressively eliminate which variables could be problem.

       As for comments on mounting, I dobut that is the problem, because
when I shoot at 65mm stereo base, I mount the left, use the grid and mount
the right, check with viewer and voila, great stereo scene... it takes me
under a minute to mount a good stereo pair.  So without going into details
about mounting mistakes, I think it is clear that proper stereo pairs mount
very fast.... my bad pairs I look through the viewer lenses for 10 minutes
straight trying to find a happy place for the right chip, but it never
happens..... As for taking mistakes, I am meticulous on leveling, checking
the levels with other levels, toe in, etc... I think the test below
eliminates all these variables.. I set up the tripod and stereo bar and did
not move it for all shots, only the cameras slid on the bar.   OK, here is
what I just completed.....

1.  Two cameras, call them A & B.  I shot the following sequence.... a scene
in my garage, no infinity... nearest thing in scene 10 ft, far was 17 ft.
Got tape measure out!  Both cameras mounted on jaspar engineering 24" bar,
solid, no sag at all, regardless of the camera positions!

2.  With stereo base 65mm, I shot camera A, then moved it over A, and shot
B.  So used both cameras and simulated a 65mm base.  Mounted and viewed
perfect.  Conclusion.... there is no mis matched cameras or lenses....

3.  Same scene, took camera A, shot left, moved it over 65mm on slide bar
shot again.... mount and viewed perfect.    Did the same for camera B,
perfect.  Conclusion, no mount problems, no individual camera problems.

4.  Next, with John B's formula, I used the near 10ft, and far 17 ft. and
came up with a 9.7" base.  Set up cameras with a 9.7" interocular distance
and exposed.  Would not mount properly.... when the middle of the scene
fused, the left and right edges become doubled up, or double vision.

5.  Did the same shot with an 8" base.... same problem.... then did it with
a 6.5" base, (the closest my cameras will come together), it almost worked
perfect..... conclusion... John B's base base was too damn wide.... can not
properly fuse the images.  The formula is suggesting bases that don't fuse
well... (at least in my experiments) also it is very difficult to conclude
when taking the shot, what is the closest thing in the scene vs. whats the
closest thing in the mount after croping...I shoot 6x7... so there is some
mounting decisions, I tried to keep it as close as possible, but this offers
some very difficult composing and mounting dilemnas.

        I can not spend any more time on this formula.  If anyone disagrees
with my conclusions of above, please do advise.... I am too new at this MF
3D  to feel confident about anything.

     I would like to know this.... maybe to prevent myself from destroying
shots, I should stick to the basic 1/15th rule.  Or to be conservative say
1/20 th rule.... take the nearest point, divide by 20, and never let the
base become greater than this value.  It seems a closer base still gives you
good stereo pairs while getting to far apart is a disaster.  This also would
be much easier to accomplish in the field.  Any input on this procedure?
What do many dual camera users out there do to determine their base?  Thank
you all..

Regards
Bill