[photo-3d] Re: Double Depth mounting...

[Bruce Springsteen <bsspringsteen@xxxxxxxxx>]

David Motz asked:
> Can someone explain what double depth mounting is?  I know I've heard of
> the term before, but have no idea what is meant by this...

It's a needlessly obscure term for a very simple technique.  It has to do
with the stereo window, so those who either don't see or don't care about
the stereo window may ignore what follows.

"Double depth" means reducing the separation between the left and right
image frames, while maintaining the same infinity separation in the
images, so that the stereo window is moved closer than the nearest object
in the image.  The term is biased toward slide mounting, as it is
concerned with over coming the fixed window distance in slide mounts
(about 2 meters in the Realist system).  Reducing this fixed distance
between stereo slide apertures is generally done either by masking off a
bit from the left of the left hole and a bit from the right of the right
hole - thereby making a narrower window and less distance between
corresponding edges of the two apertures - or by actually cutting a
vertical strip from the mount between the apertures and moving the halves
together - thereby making a custom mount with less separation between
frames.  The term double depth is an unnecessary reference to the fact
that moving a fixed "window" from two meters away to an apparent distance
of one meter has the effect of doubling the "depth steps" in the total
scene.  Don't ask what *that* means - it's a red herring.  (Dr T may
salivate at this point.)

Print makers do the equivalent fix all the time, without giving it a
confusing name.  When we see near objects violating the window in
someone's print, we will advise them to remove a bit from the outside of
each image to bring the window forward.  No fuss, no muss, no depth steps.

This is all well explained and illustrated in Ferwerda's "The World of
3-D", chapter 25, sections 3-4.  Got the book?

Best regards,
Bruce (Where shall I truncate my pyramid?) Springsteen

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