P3D Re: Cardboarding

[jacob@xxxxxxxxxxxxxx (Gabriel Jacob)]

Boris writes
> To me, cardboarding is the opposite of "stretch".  It is seen in slides (or
> prints) that are being viewed with a viewer that presents a wider field of
> view than the taking lens.  (i.e. the viewer lens f.l. is shorter than the
> taking lens f.l.)  The opposite effect, stretch, is seen when the taking
> lenses have a wider field of view than the viewer lenses (i.e. the taking
> lens f.l. is shorter than the viewer lens f.l.).

Actually squash and cardboarding are two very different effects resulting
from differing variables. Stretch or squash is caused by the camera and
viewer focal length mismatch. Squashing causes the whole distance 
(z direction) of the scene to be decreased, but this is not cardboarding. 

In cardboarding it is possible for two different stereo pairs of the same
scene to have the same depth distance, but one exhibiting cardboarding,
while the other does not. An example of this is two cameras with same
specs but one having inferior optics compared to the other. The result
is the inferior camera produces cardboarding, while the better camera
doesn't. This is due to the resolving power of the camera optics.

Just remember, there are only two D's in cardboarD! ;-)

Gabriel 


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