[photo-3d] Cloud Movement

[leroyddd@xxxxxxx]

     Take the first picture on the side the clouds are going to... shoot 
"upstream" go against the flow...

     Since all the clouds in the sky generally move across the sky in the 
same direction at the same speed, the closer clouds appear to move 
faster/farther both to the eye and in successive frames.

     This presents a similar setup to a turntable stereo shoot.

     If you're shooting the successive rotations of your subject with a fixed 
single lens camera or if you don't have the turntable/subject footing in the 
scene using a stereo camera, you don't care which you shoot first.

     You just put the chips in the way you need to to get non-pseudo, since 
all the parallax is consistent.

     But if the two rotations are shot from two different positions(the 
chosen interocular) at different times, the time parallax and the space 
parallax should match for pleasing results.
     If you do it correctly, your sidestep landscape will have a "ceiling" of 
clouds trending from somewhere over the viewers head off to the mountains... 
maybe even behind the mountains!! To infinity and beyond!! :=) Better than an 
effect of the sky running from the viewer's chin or chest up to infinity.

     We know that in our sidestep landscape the near "grounded" objects will 
be to the right in the left frame and to the left in the right frame compared 
to the positioning of more distant objects no matter which order we take them 
in.
     We want to make that happen because of the cloud movement.
     Time parallax due to cloud movement is psuedo in that the second 
exposure has near(faster) clouds farther apart than distant(slower) clouds.

     Sooo... clouds moving left to right are pseudo if mounted left first 
exposure, right second exposure and you have to swap them to left second 
exposure, right first exposure. Which is the order to take them in so that 
the ground objects agree in parallax to the clouds!!

     The trick you've done is to have "swapped" the clouds out of pseudo in 
the camera.

     I have to go thru this exercise every time... for me it doesn't seem 
right to go against the flow, but it is correct... or I might have it 
backwards... if so just reverse all the above... I see different answers in 
the digests and wanna get this right so please point out errors in my 
reasoning so I can figure a good way to remember this short of a tattoo!!!

In a message dated 3/2/01 9:00:07 PM, photo-3d@xxxxxxxxxxxxxxx (Dr. T writes:

<< Date: Fri, 02 Mar 2001 06:09:14 -0500
   From: "Dr. George A. Themelis" <drt-3d@xxxxxxx>
Subject: Quiz: Movement of clouds/direction of shoot
...You are ready to record a ... hyperstereo... the
clouds are drifting very slowly from left to
right.  ...

Question: Should you take the LEFT picture first
or the RIGHT, and why? >>

Since this is a hyperstereo, the effect might be even better than a sync'ed 
shot. Or you could "bracket" sky parallax and take the best one.

More stereo,
           LeRoy
LeRoy Barco
LeRoyDDD@xxxxxxx

 

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