Re: Converging fields of view

[P3D Gregory J. Wageman <gjw@xxxxxxxxxx>]

Larry Berlin writes:

>In a two camera shot, the center line of the lens axis matches the center
>line of the field of view. If the two cameras are maintained parallel to
>each other, and each lens has the same angle of total view, the left side
>camera will see more of the left field than the right side camera, all the
>way out to infinity.

True.  Ignoring the position of the apertures in a stereo camera, it is
also true for such a camera.

>Full frame stereo images shot by two cameras, maintained exactly parallel,
>will not display the differences you describe. Images placed in mounts will
>display a "window" wherever the masking has set it. 

Yup.  But what I have learned from this discussion is that, whether the
masking is done during mounting, like you must do with your slidebar
setup, or whether the masking is done inside the camera by the offset
apertures, the results are exactly equivalent.  You end up with Neil's
"convergent angles of view" *in the resulting images*.  That is, if you
could put your masked slides back into your camera and trace the lines
from the corners through the center of the lens at their respective
positions, you would find that the lines converge, meeting at the window
depth.  This is what it took me so long to get through my thick skull. ;-)

Of course if you don't mask, then this isn't true, but then you also
have a "window" at infinity.

	-Greg

P.S.  I feel I've been this dead horse into a greasy black stain on the
      ground, and I'll now let it drop... ;-)


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