Re: Figuring exposure on swing lense cameras

[James Young <jamiehy@xxxxxxxxxxxxxxxx>]

>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

Thanks Marty
  That should help. Most of my al-vistas have little charts giving 
speeds, but as they were done in 1900-1910, I would guess they aren't 
valid anymore.

What kind of photos do you get from your 5D. Much banding?  Are they 
fairly sharp? I just restored a 5-F which I hope to shoot with soon. 
I have a 5D that someone modified with a smaller slit, and shot a 
roll with it , but was way off with the exposure. I need to figure 
out the exposure and try  again. The 5D came from the factory with a 
f8-45 built in diaphragm. on the lense. Jamie