[MF3D.FORUM:727] Re: I need a MF 3D Dr.

[Brian Reynolds <reynolds@xxxxxxxxx>]

Bill Glickman wrote:
> 3.  When mounting the chromes, I notice something odd.... when Paul
> Talbot was here, he showed me the use of the mount gauge.  Setting
> the nearest subject to the near line and furthest to the far
> line.... Both can NOT be satisfied at once with the John B spacing.
> (Is this normal? )  And it does not matter if I mount to the near or
> the far, I still can not get everything to fuse at once.
> 

Below you mention that infinity (the horizon) doesn't appear in your
test images.  When you mount the frames so that the closest part of
the image (which may be a blade of grass in the foreground, it may not
be one of the main subjects of your composition) is on the near lines
which side of the far line does the furthest part of the image fall
on?  If it towards the near line that's OK, it just means that you are
not using the maximum amount of deviation.

> 4.  Greg Erker advised to take one camera for the left shot and then
> move it over and bring the other camera in for the right shot,
> maintaining 65mm interocular spacing.  I felt this was an excellent
> "process of elimination" test.  I did this, and voila it works.
> That is why I wonder if the formula could be ill advised.  Here is
> some examples of the near and far in feet and the stereo base in
> inches I have been using...
> 
> N   F     Base "
> 10  26    6.5
> 10  23    7.1
> 10  20    8.0
> 10  17    9.7
> 10  14   14.0
> 10  13   17.3
> 
> Maybe the formula needs tweaking???  I doubted this since so many
> people including David Lee have used this successfully?
> 

Exactly which formula are you using?  I tend to use the information in
the paper at <URL:http://home.mira.net/~kiewavly/bases.html>.  Since
you don't mention what distance you are focusing at ('a' in equation
1) I assume the maximum DOF case (equation 3).  Plugging the formula
into my HP-48SX and turning the crank, my numbers (in millimeters and
sorted by ascending far distance) turn out to be:

d = 2.5mm, f = 80mm

N (an)  F (af)  Base (b0)
------  ------  -----------------------
3048    3962.4  403.167 (15.873 inches)
3048    4267.2  325.875 (12.830 inches)
3048    5181.6  226.500 ( 8.917 inches)
3048    6096.0  186.750 ( 7.352 inches)
3048    7010.4  165.346 ( 6.510 inches)
3048    7924.8  151.969 ( 5.983 inches)

> One other tid bit they may help someone diagnose my problem.  One
> shot of a small waterfall in my backyard with larges stones sticking
> out, (as steps for the water falling) seem to appeared backwards.
> In other words, instead of the rocks sticking out at you, they seem
> to be inverted, or pulled backwards, like they were indented
> vs. protruding?  That was strange, but I felt it may provide a clue
> to solve my never ending mystery.
> 

This is pseudo-stereo.  You have the film chips reversed (the left
chip is where the right one should be).

-- 
Brian Reynolds                  | "Dee Dee!  Don't touch that button!"
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http://www.panix.com/~reynolds  |    -- Dexter and Dee Dee
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