Re: [photo-3d] shadow 3d?

["John A. Rupkalvis" <stereoscope@xxxxxxxxxxxxx>]

----- Original Message -----
From: "marble" <marble@xxxxxxxxxxx>
To: <photo-3d@xxxxxxxxxxx>
Sent: Monday, November 20, 2000 9:56 PM
Subject: [photo-3d] shadow 3d?


> Hiya,
> does anyone know of any online pictures (or resources) on shadow 3d?
>
> Explanation:
>       set a chair in the middle of a dark room.  shine a light on it.
take
> a picture of the shadow of the chair on the floor.
> 2) dont move the camera, just move the light.  take the 2nd picture.  the
> shadow will be in 3d, right?
>
>
> I have seen a book on stereo shadow 3d, but was wondering what else is out
> there.
>
> Cherio

This subject, or several closely related ones such as silhouette 3-D, time
parallax, etc., have appeared in several writings published over the past
century-and-a-half.

Abstract 3-D is a fascinating area, under which this category falls.  Those
of you interested in stereoscopic abstract art should be encouraged to
experiment.

One of the reasons that abstract stereoscopic imagery is nearly (but not
quite) rare, is that it is very difficult to do convincingly.  Once we lose
other visual depth cues, the human brain tends to interpret the image as a
visual error, unless it is very carefully done.

This often occurs when something in an image changes between the time the
left-eye image is created and the right-eye image is created.   An example
would be when a person shoots a hyperstereo pair with a single monoscopic
camera, by shooting one picture, and then moving the camera laterally to
another position and shooting a second one.  If something in the image (such
as an airplane or automobile) moves between exposures, it will appear to
"jump out" of the picture, in an unnatural fashion.

This effect (and others) should be considered when making stereo
shadowgraphs.  With considerable thought, skill, care (and luck), they can
be made convincingly.   Probably several attempts to create that special
work of art.  But, if you are successful, you could easily win some awards.

JR