Re: fixed focus panoramic

[Andy Buck <buckwiet@xxxxxxxxx>]

David & Simon -

Thanks very much for your responses.  What little I
understood I think is helpful. However, I am sure I
don't understand DOF parallel and perpendicular to the
slit - ?

After I sent the note I did two things: Thought about
my experience with a Hulcher and did some
calculations. I came up with the following
conclusions.

1. With the Hulcher, I used the 55mm lens and the 15'
focus spool.  I focused the lens at 15' and closed
down to 22. I got wonderful DOF and everything is
sharp enough from under 8' to infinity (actually very
sharp) at 3x magnification, the most I will do. I
figure that on the Hulcher, the rotational
axis/distance/whatever doesn't change, since all you
do is change a spool, which affects film movement
speed, and focus the lens, i.e. move it farther from
the film. The two combined match up and create a sharp
image.

2. I calculated the difference in image length with
the 90mm lens between focusing at infinity and 15' to
be 7/16"! or, 22.5" vs 22.07".  That little a change
probably wouldn't affect sharpness *much* especially
contact printed or 2x magnification, even if I didn't
change it!

So, I have decided to: move the lens out 1.75mm to
focus at 15', maintain the rotational axis point found
by focusing at infinity, and move the film at a rate
of 22.5" per revolution.  What do you guys think of
that plan?

Thanks, again!
Andy


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