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Thread: Zone plate design

  1. #1

    Zone plate design

    Okay, I am new to this site and have just completed my first 4x5 pinhole camera build using a 'skink' .3mm pinhole. The pancake holder for this can also hold zone plates, and after doing some looking on this site, have convinced myself to try it out. I am quite out of my depth when it come to zone plate, but I get the idea of how it works etc. That said, I need to know how many rings I need in a plate, and I have no idea how you figure that out. What's the best design for max resolution etc.
    I see the pinhole calculator site has ZP fields but like I said, I only know enough to be dangerous!!

    I want to use my 45mm 4x5 for both pinhole and zone plate and having both options seems like a plus to me. I love the sort of poor mans 'Verito lens' look that zone plate gives to an image. Any ideas??

    Thanks

    A.

  2. #2
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    Zone plate design

    Andrew,
    To design a zone plate you first need to know the distance from the zone plate to the film plane; the focal length. Next, zone plates are wavelength specific; so, you need to pick a wavelength for the zone plate. Most people pick 550 nanometers because it tends to be close to the middle of the visible spectrum.

    With regard to zone count; I notice most people tend to use between 5 and 9 zones.

    With this information; you can use any of the available zone plate designers for your zone plate.

    There is information on the process I use to create zone plates on my web site:
    http://www.markgavin.com/site/zone_plates.php

    Regards.
    Mark

  3. #3

    Zone plate design

    More zones = more "glow". You might want to experiment a bit.

  4. #4

    Zone plate design

    Here's a process of making zoneplates, which you can make several and experiment a bit to see which fits your needs.
    http://cline-company.com/blog/?p=21

  5. #5

    Zone plate design

    Just curious :

    How does it come that zoneplates are always in Black-and-White whereas they are ideally fitted just for one colour (wavelength) ?

    Has anybody tried to make zone plates in different superposed colours for (let's say) three different wavelengths ?

    Or doesn't it work (this way) ? Why not ?

    Paul

  6. #6
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    Zone plate design

    The zone plate works by alternating opaque and clear areas. Black and white high contrast film gives good opacity and good clarity both. Color negative film offers neither opacity nor clarity. Color reversal film might give you the clarity, but not opacity.

    Zone plates are all the same - a central pinhole surrounded by alternating clear and opaque rings, each with the same area as the pinhole. Zone plates are 'tuned' in only one way - varying the diameter of the central pinhole. Actually, a pinhole is merely a special case of a zone plate - it is a zp with only one zone.

    The ideal zone plate would be alternating infinitely thin rings of black metal and open space, but that would be a bit difficult to pull off. (Does anyone know of a zone plate made this way with very thin 'ribs' to hold the rings in position?)

    I like the idea of a photon sieve made in metal, as an array of holes is possible to make, unlike an array of rings. The hole sizes necessary are very small, the metal would have to be very thin, and I am afraid that the cost would be prohibitive. I wonder if the ems aperture people make custom grids for a semi-reasonable cost . . .

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