P3D Re: Fatous Formula, Re: double depth

[abram klooswyk <abram.klooswyk@xxxxxx>]

CanterMike wrote:
>I'm still a rookie at this and am unfamiliar with the expression 
>"double depth".  Could someone please explain?
Tom Deering:
>It's a way of moving the stereo window by masking off the ends of a
>standard mount.  Seems like an awful lot more work than keeping a chart 
>in your camera bag.

"Double depth" is a term Koo Ferwerda borrowed from Earl Krause, 
who used it in his underestimated little book "Three Dimensional 
Projection" (Greenberg, New York 1954).

In the 5P mounting system it indeed means masking off identical strips
at 
the outer side of both apertures of a standard mount, or alternatively,
remove a center strip from the mount, in both cases bringing the viewing 
stereowindow closer. 
This means in fact for the 5P system not a 1/30 base but a 1/15 base.
So depth range not from infinity to 2 meter (7 feet) but to one meter.
The f-stop required for this depth range could also be used in more
close
focussing, with far point closer than infinity.

Again, why it's called "double depth"? It's only ONE meter more than the
almost infinite space between infinity and two meter?
Believe it or not, the perceptible depth between one meter and two meter
is equal to the depth between two meter and infinity. 
In viewing, when looking from infinity to two meter your eyes swing a
certain angle, together about 2 degrees. When they swing two degrees
more, you are looking at a point at one meter. Stereogeometry is about
angles in viewing stereopictures. Stereo is for viewing.

Earl Krause, Koo Ferwerda and others recommanded the technique for
careful
use in scenes with lots of interesting stuff at all distances.
Keeping a chart in your camera bag probably will hold you back from a
number of interesting, still projectable shots.
Don't use the Fatous Formula.

Abram Klooswyk


in viewing your  
OnlyOr used


------------------------------