Another (different) Zone plate question

Hi all,

This may sound like a strange question, but I was
wondering if there is a constant (and known)
relationship between the image size created by a
pinhole or zone plate of a given focal length
(pinhole/film distance) on the one hand and a given
camera and lens combination on the other? Is there a
formula that would be of use here?

What I mean is this. Say, for example, I take a photo
of an object using a 6x4.5 camera with an 80mm lens
and position the object so that it exactly fills the
frame (6cm top to bottom) and is centered and
occupying half the frame the other way (leaving
1.125cm on either side of it--my theoretical object is
thus a rectangle of 6cm x 2.25cm on the negative). If
I wanted to create an image of the same object exactly
the same size and in the same position on another
negative but using a zone plate or pinhole, is there a
simple rule I can use to position the second camera?

For example, can we say that a 75mm zone plate will
create an mage of equal size if positioned roughly the
same way but half the distance to the subject--or
something like that. Maybe instead, could you do this
with the zone plate camera in an identical position as
the lens camera but using a zone plate of a focal
length that is a constant multiple of the lens focal
length--say 1.28 times (that's completely made up),
which, in this example, would give 102mm (80mm x
1.28).

I imagine the situation will be different for pinholes
and zone plates?

If this makes sense and anyone can help, I'd be
grateful for any ideas.

Thanks

Colin

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Received on Thu Mar 18 13:51:49 2004