Re: Vertical misalignment

[P3D Dr. George A. Themelis <fj834@xxxxxxxxxxxxxxxxxxxxx>]

John B. writes regarindg BobH's question on tiliting the camera:
>
>Sure you have vertical misalignment, or more properly vertical parallax, 
>_within_ the chips if you tilt the camera.  

What is the definition of misalignment or vertical parallax _within_ the 
chips?  It is confusing to call "misalignment" something that is subjective
or requires a frame of reference to be observed.  If I tilt the camera, one
lens is higher than the other with respect to the ground, not the film
plane.  If this is the viewing point that I chose to use, why call it 
"misalignment"?  If there is no frame of reference in the picture, who
knows or cares about it?

>This is easily confused with 
>a vertical misalignment _of_ the chips which occurs in mounting or if 
>the lenses of the camera are level but the gates are not (one gate higher 
>than the other) and this is not corrected in mounting.

Things are getting even more confusing here... If one gate is higher than
the other, how can you confuse this with a tilted camera?  In a tilted
camera, the horizon is not level.  When one gate is higher than the other
then the horizon is level but there is a vertical paralax that can be
eliminated with proper mounting (why "not corrected in mounting?")

Alignment in the eyes of the observer is a complicated situation since you
have the following string of objects that can be aligned or not in respect
to each other:  real scene, camera lenses, film plane, chips in mount,
mount in viewer/projector, viewer/projector lenses, eyes of observer.  It
seems to me that the worse factor introducing misalignment and vertical
parallax is non-matched lenses (camera and/or viewer).  Everything else can
be fixed one way or another.  The alignment of the scene w/respect to the
camera is subjective and out of the question, the alignment of the lenses
with respect to the film plane can be corrected during mounting, the
alignment of the chips in the mount is a matter of proper mounting and the
alignment of the mount with the respect to the viewer lenses is a matter of
proper maintenace of the viewer/projector.  Finally if the person viewing 
the stereo image insists in tiling his head, then that's his problem.

-- George Themelis


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