[photo-3d] Trick/Creative photography in 3d - Part III

["Dr. George A. Themelis" <drt-3d@xxxxxxx>]

We continue with the 3rd and last installment of this
interesting stereo techniques topic....


*** Multiple Exposures with Split Fields

The next degree of difficulty is to expose different areas of 
the film at different times.  To do this, the lenses must be 
covered in a well-controlled way.  

There is at least one commercial unit from the 1950s, the 
"Powers Trick Adapter" which was made for this type of work 
(the Powers company was located in Cleveland OH).  An adapter 
plate fits over the stereo camera (different versions for 
Realist and Kodak stereo exist) and different masks are 
inserted and removed, for split-field multiple exposures.

Even without such a device, it is easy to use black tape over 
a lens shade to cover, say half the lens.  Take the 1st exposure, 
tape the untaped part, remove the old tape and take the 2nd 
picture.

Split fields can make the "twin" pictures more interesting 
(no dark background is needed).  Another common example are the 
"bodiless person" pictures.
	
** Multiple Exposures with Size/Space Control

The size of an object is controlled by its distance from the 
camera.  For example, to put the lady inside the bottle you 
must photograph the bottle at a close distance and the lady 
from far away, to make the lady smaller than the bottle.  
But in stereo, you must also "pull" the lady closer to appear 
inside the bottle, not behind it.  This is achieved by changing 
the spacing of the lenses in each picture.  

In last year’s Tutorial (4.6, February 2000) we discussed the 
effect of the stereo base and mentioned that the entire scene 
moves with respect to the observer in a way proportional to 
the stereo base.  For example, doubling the stereo base will 
pull the scene twice as close.  Reducing the stereo base by 
half will double the apparent distances of the scene.  By 
controlling both the distance and the stereo base we can bring 
the lady inside the bottle in way which appears perfectly 
normal in stereo viewing.

Sounds easy in theory but applying "size and space control" 
in practice is rather complicated.

*** The Sandwich Approach

So far we have discussed techniques for recording multiple 
images on one piece of film (two actually since we do this 
in stereo).  An alternative is to record two separate pictures 
and then put them together to make one image.  By placing one 
piece of film over the other, we create a photographic 
"sandwich".  This is similar to a double-exposure only now to 
avoid the "ghost" effect you need a light background, instead 
of dark.  

For example, you can photograph an ordinary scene with a 
featureless sky in stereo.  Then use a long lens to take a 
picture of the moon during the day, being careful to wash 
out the sky.  Then overlap the large moon over the sky in 
the stereo picture. (A variation of this is Mark Dottle's 
technique of adding "film gels" for creative colors).

When creating a "sandwich" in 2D, one has only to worry about 
the relative placement of the images.  In stereo however, in 
addition to the placement, one has to worry about the vertical
alignment of the right (R) and left (L) images and the 
interaction of the two images in the stereo space.  This is 
controlled by the horizontal spacing of the R and L chips. In 
the example of the superimposed moon, we can change the 
location of the moon from the foreground to the background 
by changing the changing the distance of the R and L film 
chips.  (Normally we would like the moon to be at infinity.) 
So in stereo we have an extra layer of control and difficulty 
when superimposing images.

*** The Darkroom/Projection Approach

Multiple exposures can also be created in the darkroom (for 
prints) or during slide copying or by projecting different
images and then photographing them.

There is also the possibility of split fields and a lot of 
room for creative work in manipulating one or several stereo 
images.  Again, working in 3D is much more complicated than 
in 2D.

*** Computer Manipulation

This is an area in which I have absolutely no experience.  
But I can see how the computer is the ideal tool to 
revolutionize trick photography. You still need stereo 
images to start (unless of course if the image itself is 
computer-generated) but the computer gives you the means 
to examine multiple possibilities, before committing to 
printing.  

Next Tutorial:  Twin Cameras in Stereo (input from photo-3d
members is created appreciated).

This Tutorial was brought to you courtesy of the Ohio
Stereo Photographic Society.  Our newsletter is the
award winning Stereogram, published monthly from 
September to June.

George Themelis
Stereogram Editor



 

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