Re: [photo-3d] Re: Quiz #3 - stereo window

[Peter Davis <pd@xxxxxxxxxxxxx>]

At 11:24 PM 8/31/2000, you wrote:
>George writes, in part:
>
>  << To place a better stereo window you must crop the left side
>  of the left picture and the right side of the right picture
>  (in equal amounts).    >>
>
>
>Did I miss something, or isn't that backwards?
>
>Since we accept that the Left sees Less on the Left, don't you need to trim
>the extra from the right side of the left image, and the left side of the
>right?  What does it accomplish to take image away from the left side of the
>left image, since there is already less there to start with?

No, this isn't backwards.  Imagine there's a tree to the left of the 
photographer.  The right lens may miss it completely, but the left lens may 
pick up part of the trunk on the left edge of the shot.  Therefore, you 
would trim the left edge of the left shot.

Put another way, imagine you hold a playing card up to your nose, sticking 
straight out.  You left eye will see whatever side of the card is facing 
left, and the right eye will see the side facing right.


>As I write this I hold in my hands an untrimmed set of prints fresh from the
>lab (didn't think I could type & hold prints at the same time, didja?) and
>when I match up the nearest (foreground) set of homologous points the right
>edge of the left print clearly hangs out past the right edge of the right
>image.

Was this pair taken with a twin rig?  Might the lenses have been "toed in" 
slightly?  Alternatively, is it possible the prints were slightly cropped 
in enlarging?  Otherwise, I don't see how *parallel* lenses would allow the 
right edge of the left image to extend past the right edge of the right.

-pd


--------
                              Peter Davis
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                "The artwork formerly shown as prints."
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