Re: slit cameras?

----- Original Message -----
From: "Tom Miller" <twmiller@mr.net>

> The format for the two images is 4x5. The rule of thumb I heard was
> to "meter the scene at f90 and give it two more stops."

This means your slits set up is f/180

> This gives
> exposures of 1 or 2 seconds in bright sun with Ektachrome 64T (EPY).
> The few pinhole exposures I've made with 4x5 EPY were in the 16 second
> range. Naturally the slit exposure times can vary depending on the
> width and length of the slits; but I've found that this rule of thumb
> works well in almost all cases.

I'd say the widths alone affect the exposure time. The lengths and distance
between them affect the image circle size or angle of view.

Tom, if you know the widths of the slits of your camera, could you do me a
favor? Could you please substitute the focal length and width of slits in
the following formula and find the result?

f/stop = 0.886 x focal length / SQRT( A x B )

where SQRT stands for Square Root, A is the width of one slit and B is the
width of the other slit

Is the results anywhere close to f/180? (close in this case means above 128
and bellow 256)

Many thanks,

Guillermo
Received on Wed Nov 7 10:28:23 2001