Re: Waack nomographs, etc.

[bercov@xxxxxxxxxx (John Bercovitz)]

Ted Gosfield asks _many_ good questions which I will paraphrase.
 
> Can this be the beginning of _obsession_?
 
If you're fortunate. 
 
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The Kodak, like most stereo cameras, is only going to give you 
more depth of field under lower light conditions with faster film.  
Its short lens helps the DOF but it isn't a cure-all.  It is too 
bad it doesn't have any slower speeds but I guess the great yellow 
father thought of it as more of a consumer item.  In today's world 
all the controls it has would put it at the pro level of expertise.
(I don't think I'd call it a point and shoot since you have to 
adjust f/stop, shutter speed, and distance.)  
 
As you suspect, a FED is a step up in some ways.  It has 
autoexposure but it doesn't have a slower shutter speed than the 
Kodak.  The FED's lenses are quite good but the mechanics are 
terrible.  However, there's a guy on this list (Hi Joel) who can 
bring it up to par.  I don't worry about it not having autofocus 
or a rangefinder because with a lens this short stopped down this 
much, you really can judge distance plenty well enough for even 
critical shots.  The autoexposure is great for a guy like me who 
is fussy about exposures but doesn't have the calibrated eyeball 
of Dr. T.  8-)
 
For optics, the Belplasca's lenses are as good as a modern SLR's, 
the FED's are that good in the middle but go a little softer 
towards the edges.  The Kodak is also good in the middle and falls 
off in the corners.  I've heard the common Realist's lenses are on 
a par with the Kodak's.
 
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Fritz Waack's nomographs are based on the following formula but 
with some simplifying assumptions which tend to make it inaccurate 
at close distances.  Here is the unabridged formula:
 
             an*af 
b0  =  d* [ ------- ( 1/f  - 1/a) ]
             af-an 
 
b0: This is the maximum tolerable separation of the camera's 
lenses.
 
d = Maximum allowable on-film deviation for a given format.
              Realist format  = 1.2 mm  
              35mm Full Frame = 1.7 mm   
              Medium Format   = 2.7 mm
 
f = The focal length of the camera's lenses.
 
a = The distance at which the camera is focussed.
  
af: distance from the camera lens to the farthest object in the 
scene.
 
an: distance from the camera lens to the nearest object in the 
scene.
 
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Loupes.  The power of a loupe is generally:
(250 mm/lens focal length) + 1
though rarely the 1 is left off.
So a 5X loupe will have lenses with focal length about 62 mm.  
This is very long to view something taken with 35 mm lenses.  
You will see a lot of stretch in foreground objects if you use 
this lens.
 
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You set the window by shifting the lens away from the center of 
the image.  In a view camera, you can use the shift adjustment to 
do this.  In an ordinary stereocamera, it's already been done; 
it's built in.
 
A way to remember which way to shift the lens is to remember that 
in a stereo camera, the lenses are closer together than the film 
gates (image apertures).  So when you take your left-eye shot, 
shift the lens right and vice versa for the right-eye shot.
 
John B
 


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