Re: Double depth - definition

[T3D Larry Berlin <lberlin@xxxxxxxxx>]

john bercovitz  writes:
>.......snip.........
>I'll try a short explanation of my own.  If you have too much depth 
>in a scene, you can increase the separation of the chips until the 
>nearest object is behind the window.  This works fine (in my 
>experience) as long as you don't have your infinity homologues 
>significantly more widely separated than the lenses in your viewer.  
>(It is entirely possible to increase infinity separation. 
>......... snip.....
>Another way to do the same thing is to leave the infinity homolgues 
>at the standard 63.4 mm on center but decrease the mask aperture 
>separation, by, say, 1.2 mm.  You can decrease aperture separation 
>by doing surgery on the mask or by crop an equal amount from the 
>left side of the left aperture and the right side of the right 
>aperture.  This approach is called "double depth".

 I just figured out what this accomplishes. Thanks for the explanation.

>Both of these methods will put the nearest object behind the window 
>when there is more depth than allowable under the existing rules 
>(62.2 & 63.4) in the scene.  However, in projection, the former 
>solution causes divergence and the latter solution lifts the stereo 
>window off the screen.

Another 3D term that doesn't quite mean what it sounds like.
It doesn't even really *fix* a problem of *too much parallax,* which would
still exist. The ideal approach, of course, is to not have too much parallax
in the image to start with. With today's tools you could put those images
into your computer and *fix* the parallax problem in the images themselves
then reconvert to film. This would be a much more ideal solution if the
problem is severe enough and worth being fixed. 

It is this capability in the computer that makes it the ideal 3D compositing
tool (aside from the time and effort involved). Every element placed in the
scene can have an ideal set of parameters in terms of parallax, making
object parallax relatively independent from depth parallax and all of it
within the ideal usable range. This idealizes the process of stereography in
a functional way, almost like the ideal optical geometry of the SEM 3D
process previously discussed. 

Larry Berlin


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