Re: [photo-3d] Re: mounting to the window/infinity

[Paul Talbot <ptww@xxxxxxxxx>]

Patrick Boeckstijns wrote:

> This may be a stupid question.
> How do you most people set the window ? I know the theory !

No, definitely not a stupid question!

> Now I use the plexi "Spicer mounting device" and off course
> the Spicer mounts.
> Before I just used a "light box/table".
> In order to mount correctly and set the window I used the transparent jigs
> from REEL 3D.

I think by "transparent jig" you mean the mounting gauge, right?

> I fixed one chip and then made sure the near-points and infinity points
> were located inbetween the two reference lines on the right. I shifted the
> chips until they did and then taped them.

That's a good basic (though mechanical) approach.

> With the spicer device, using also the transparent seems complicated.

How so?  It is a good idea to tape a mounting gauge to the
Spicer mounting jig.

> Do most people set the window just by looking at the pair and adjust until
> they like it.

Some people mount to constant infinity, and let the window
fall where ever it may.  Among those who mount to the window,
I think the more experienced (and more particular) mounters
let their eyes tell them when the window is set correctly
Sometimes this can be done using just the rule of 3Ls, but
often it is best done by viewing in 3D.

> In the beginning I used to do that but it seems I developped a way for my
> eyes to compensate for mounting errors. Slides that looked good to me were
> a problem for others. When I checked them with the transparent it was
> obvious the infinity points were diverging to much.
> Does all this makes sense ?

Yes, it does make sense!  If, however, you have set the window
correctly, you should only have excess infinity spacing if there
is "too much depth" in your photos.  If you kept the total depth
range within the usual 7ft-infinity guideline (10-ft to infinity
to be more conservative), you will not have excess infinity spacing
when mounting to the window.  The excess spacing problem arises
when something is too close to the camera, and the chips have
been pushed farter apart to keep the closest objects behind the
window.  (If infinity is not in your photos, you should use the
DOF scale on your camera, as described by Charles Piper, to limit
the depth range in your photos.)

Note that when mounting to the window, it is a good idea to still
use a guage to check that the infinity spacing is not too large,
precisely for the reason you mention.  Experienced stereo viewers,
especially those who can freeview, are likely to be able to handle
some divergence when using a stereo viewer.  Less experienced 3D
viewers may have problems exactly as you describe.

You mention above "it seems I developped a way for my eyes to
compensate for mounting errors."  Personally that is one reason
I would never rely on a SAM to determine when my mounting is
correct.  Viewing in 3D is great for setting the window, and
the SAM would make that easier.  But I would never rely on 
viewing an image in 3D through a viewer or SAM to check for
vertical and rotational error; while my eyes would pick up
large errors, they would compensate for smaller errors as you
describe.

Vertical error can often be checked using the top and bottom
edges of the mount, by looking alternately at the left and
right images.  Some images (e.g., ones with plain sky at the
top) are difficult to check using the mount apertures, and
a gauge is needed.  Personally, I find rotation error (unless
extreme) almost impossible to check without a gauge.

Paul Talbot