----- 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
