Re: Figuring exposure on swing lense cameras

[MMagid3005@xxxxxxx]

Jamie -- The effective shutter speed of swing lens cameras is found by 
dividing the width of the slit by the speed that the scene passes each point 
on the film.  That speed is determined by dividing the length of the film 
that is being exposed by the total time it takes for the lens to make the 
exposure.

For example, on my Al-Vista 5D with a #1 fan, it takes 11 seconds to traverse 
the 16".  The speed is therefore 16/11 inches per sec.  The slit is 1/2" 
wide.  Therefore, the effective shutter speed is (.5 X 11)/16, or .34 sec., 
or 1/3 sec.

The effective shutter speed (approx.) for no fan and for all the fans on my 
5D are as follows:

none  1/12 sec.
#1     1/3 sec.
#2     1/2 sec.
#3     6/10 sec.
#4     7/10 sec.
#5     9/10 sec.

The lens is f/13.  The two Waterhouse stops make it f/16 and f/29.

Marty Magid