P3D Re: Mounting Guides

["Dr. George A. Themelis" <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Mark Hatfield is a "long distance" member of our club... He could not
attend our mounting workshop.  But, assistance is only one email
away :-)  I will try and reply to his questions...

>I suspect that the separation of the near-point vertical lines on the 
>mounting guide is directly related to the mount being used. 

That's true, but most stereo mounts are made following the same
standards.  There is a small difference between Albion/Cardboard and
RBT mounts but for most practical purposes the same mounting gauge
can be used.

>If I wanted to try and produce my own guide would I separate the 
>near-point vertical lines by a distance equal to say right edge to 
>right edge window separation of the intended mount? 

That's correct.

>what is the proper offset for the far-point vertical line. 

1.2 mm (recommended)

>once the guide is produced can it be photocopied onto clear stock such as 
>used for overhead projectors.  My concern is that the copying process 
>could produce some errors, i.e., either enlarging or reducing the image 
>slightly. Your thoughts?

You are correct.  Photocopying WILL introduce distortions.  And since
the distance between far and near lines is only 1.2 mm, even small
distortions can have large impact.  I recommend that you purchace the
ready-made mounting guides that Reel 3-D sells.

>I have heard the phrase "stereo window set at infinity" used recently. 
>What does this mean and how do I identify it when I see it?

This is a mounting error.  If objects at infinity at at equal distances
from the edge of the mount then obviously the stereo window is at 
infinity and everything else is in front, which is a terrible way to
mount slides (if a single stereo camera is used in a slide bar, the
window will be at infinity by default... it must then be corrected
by proper masking during mounting) How can you tell?  If the pair
is mounted with most objects behind the window then the THREE "L"
rule applies: "The Left eye sees Less in the Left side" (I have
trained myself to look at the left side of the right eye which must
see more.... but this is the same.)  If the window is incorrectly placed
at infinity then the opposite of this rule apply: "The left eye
always sees more in the left side" and there are disturbing, non-
stereoscopic bands in the sides of the image. (Many older stereo cards
were made with window at OR BEYOND infinity... the makers did not
realize or appreciate the concept of the stereo window.)

Hope this helps!!!

George Themelis



------------------------------