- Original Message -
From: Gordon J. Holtslander hol...@duke.usask.ca
some quick questions for the zone plate experts.
I am not an expert nor claim to be one, but your questions are right up my
alley!!
tedious. 1/2 hour for somewhat under-exposed negatives in direct afternoon
sun. I want to speed this up somehow.
How much faster does a zoneplate work than a pinhole on average?
They are as fast as you want/make them to be, at a price tho. The more
clear rings they have the faster they are, but the larger the noise/signal
ratio.
I want to try making a zone plate for this and other cameras. I was going
to make the zone-plate on ortho film. I am wondering if its possible to
make one master zone plate image and project from an enlarger, this image
onto another sheet of ortho to scale it up or down make zoneplates for
diffferent focal lengths.
I think is doable, but I rather take pictures of a paper zoneplate at
different distances with a 35mm SLR camera.
I guess this depends upon whether or not the zoneplate for different focal
lengths is proportional the same. Is it? Or is the ring relationship
unique for each focal length?
They are proportional. If B is the intended ZP focal length, A is the
master ZP focal length and C is given by C = B/A then the ring diameters
formula for Zoneplate B will be:
D = Da * SQRT(C)
where Da = ring diameter for master zoneplate.
(complete explanation upon request)
Is the sharpness of the zoneplate image governed by the number of rings?
How close can one get the resolution of an image created with an ideal
pinole diameter?
Very close, just reduce the # of rings until you are satisfied with the
sharpness, but then you are trading off fastness for sharpness
My other question is has anyone had success creating and outputing these
completely digitally -Is there a printer that can create a fine enough
resolution image to make good zoneplates?
I think Zernike makes his ZPs digitally, don't hold your breath waiting for
him to contribute to this or any other thread, though (hope he proves me
wrong!!). If I were to speculate. he may have a comercial image setter shop
giving him a complete sheet of film with lots of ZPs of different focal
lengths as output from a digital file he may produce with Corel or similar
program. I never seen one (digitally produced ZP) but I guess they have
jagged edges compared with analog made ZPs, that may or may not have any
consecuences on the final image they produce. And no, I don't think a
consumer or low end comercial printer would work. Should you find the
opposite, let us know, pls.
Guillermo
