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Lazarza
06-06-2007, 09:51 AM
I'd never seen pictures taken with a zone plate camera until I found f295, and, as I love the pictures you all take, I've been googling and wikipedia-ing like mad to try and find out a bit more about the subject, but information is scarce.

I've seen what the pattern of a zone plate looks like, with concentric circles or dots but what are they made of? Does anyone have a picture of one? How on earth do you hold the circles together?

Another thing that I can't get to grips with is the idea that you focus them - how??

If anyone could solves some of these mysteries for me I'd be grateful - it's driving me a bit mad.

gneissgirl
06-06-2007, 10:36 AM
I share your pain! ;D You're describing exactly my questions when I first read about zone plates. I couldn't figure out what holds the rings together :D
Really, a zone plate is just a black bullseye pattern (concentric rings) on a transparent base. The number, spacing and width of the rings determines its "focal length", or effective aperture. Similar to making a pinhole of the appropriate aperture for the camera you intend to use it in, you create a zone plate of an appropriate pattern for the focal length of the camera so there's no focusing once it's in place. Different patterns produce different degrees of fuzziness/luminosity. Usually they're made photographically on high-contrast film. You can buy them from pinhole resource or make your own. There's a thread somewhere around here from maybe a year ago about making them. I know cnmne (among others) makes his own. They're pretty tiny, only a few mm in diameter.
Here's a web address that might help you understand.
http://www.whizkidtech.redprince.net/zoneplate/
It's all a bit magic to me, and I've just now pretty much told you all I know, but maybe cnmne or daryl or erin (or...many others!) will jump in and help out.

Lazarza
06-06-2007, 01:24 PM
Thank you!! Well now you've told me, of course it makes sense that it's printed on something clear. And to focus you have to make sure you're the right distance away from what you're shooting, as well as having the right zp for your focal length.

The link is fantastic, I've bookmarked it and will go back to it as I figure things out. Right now the maths is a bit bewildering, but I know a whole lot more than I did this morning.

I am glad that you don't have to be able to create one to use one though....

Andrew
06-06-2007, 04:45 PM
Hi >L<

and now for something completely different, you can go look up "pinhole sieve" too :D



I share your pain! ;D

NO GG... WE'RE HERE TO SHARE THE LOVE, DARLING !!! :D :D :D

murrayatuptowngallery
06-07-2007, 02:27 AM
I asked Lenox Laser (Doug Jannsen?) if they could make a 'hollow' metal zone plate. Such things exist for 'soft' x-ray focussing. They have to be less ideal than the concentric circle type everyone uses for photographic zone plates because they need 'spokes' to keep the concentric parts where they belong from moving. Imagine concentric rings of copper interleaved with gaps, then little 'tabs' at 120 degree intervals keeping the spacing correct. The 'spokes' alternate, one set 'up', next set 'down', and so on.

Doug said they were working on a glass one with metal deposited on a glass plate. It was unfortunately estimated to cost about $150 (each).

I also asked a manufacturer of the commonly used electron microscope grids about their capability of making spoked zone plates thru electrodeposition and they thought it was possible from computer artwork, but the setup cost was about $500-1000,

I had been wondering if elimination of the not-entirely-clear film zones would improve sharpness, but the obvious answer to that is why make a zone plate sharper - just use a pinhole. I dropped that idea.

Lazarza
06-07-2007, 05:38 AM
So does the softness come from the film not being completely clear or from the design. I did think that they were either metal with struts or glass, film had never occurred to me.

Andrew - you're messing with my mind, aren't you?

Andrew
06-07-2007, 06:00 AM
yeah, trying to.... ;D

now what will really test you is trying to punch a sieve into some brass shim by hand ;)

I think some of the softness is from the film base because I've seen example pics on the net taken with a single hole in film base (ie without the surrounding rings) and it was softer than a pinhole of similar size in brass

but primarily you have the spread of light coming from the surrounding rings...
and with the way people use zone plates for pinhole photography, I think this is "defocusing" more than "focusing"

Lazarza
06-07-2007, 08:24 AM
I see that pinhole resource sell a zone plate cap for Minolta digitals that they say fit Minolta film slrs, so I could add that to the enormous and ever expanding list of things I would like to own one day!

And, by the by, I could now pick both a pinhole sieve and maybe even a photon sieve out of a line-up, but have no plans as yet to start stabbing innocent bits of brass.

Thanks everyone for the info!

Andrew
06-07-2007, 08:53 AM
or, get a generic brand body cap and have a little DIY fun :D

Lazarza
06-07-2007, 10:59 AM
Apparently DIY is the most dangerous hobby in the UK. It's all those people trying to stab tiny, tiny holes into bits of metal. Honest.

Andrew
06-07-2007, 05:54 PM
now, don't you worry 'bout that.... ;)

GLSmyth
06-08-2007, 04:27 PM
and now for something completely different, you can go look up "pinhole sieve" too :D

What's pinhole sieve?

Oh wait, I just looked at my avatar. <g>

Cheers -

george

Andrew
06-08-2007, 05:57 PM
What's pinhole sieve?
Oh wait, I just looked at my avatar. <g>
Cheers -
george

yeah, I had noticed that before... uber_cool dude :D

Andrew
06-08-2007, 07:01 PM
eureka, I found it !!! how about the whiz kid for zone plate/ sieve design?

http://www.whizkidtech.redprince.net/zoneplate/

there's a choice to design either zone plate or "megapinhole" [= sieve]

thank you Adam Stanislav whoever and wherever you are

taco
06-09-2007, 06:03 PM
I share your pain! ;D ]

NO GG... WE'RE HERE TO SHARE THE LOVE, DARLING !!! :D :D :D
Andrew, you are a dirty old man, Mary is far to young for you ;D

Andrew
06-09-2007, 07:42 PM
Andrew, you are a dirty old man, ~~~ ;D
and I'm only getting worse !!! :K)

murrayatuptowngallery
06-09-2007, 11:36 PM
ZP trivia

Hopefully there is some how-it-works info on Zone Plates somewhere - I think they act like a Fresnel lens, which I think may be a diffractive lens rather than refractive. This probably touches on the reason why a zone plate is somewhat more focal length sensitive than a pinhole

The concentric ring spacing and possible width are based on the Airy disc spacing that diffraction theory predicts for a round aperture's diffraction maxima and minima (one of the Bessel math functions).

I haven't checked to see if a typical zoneplate in practice has non-linear spacing. The theoretical Bessel max/min spacing for a circular pinhole aperture and correspondingly a round zone plate predicts concentric rings at unequal spacing.

For a square hole, the function is sin x/x which has linear spacing. If someone made a square zone plate (concentric square rings), they sould be equally spaced.

I think the pinsieve substitutes the cluster of holes for the complete zone plate rings, but their position is based on the Zone plate.

I don't know if the pin sieve is an artistic interpretation and combination of the theory or if it has a scientific origin also.

So simple, but so complex...

pob
06-10-2007, 05:37 AM
The surface of each ring is equal to all the others. So it's a square root decrease in radius.
It is made for a certain wavelength and focus. Read more here:

http://en.wikipedia.org/wiki/Zone_plate

http://ca.geocities.com/penate@rogers.com/zoneplate.html
http://ca.geocities.com/penate@rogers.com/sieve/photonsieve.html

gneissgirl
06-11-2007, 01:09 AM
eureka, I found it !!! how about the whiz kid for zone plate/ sieve design?

http://www.whizkidtech.redprince.net/zoneplate/

there's a choice to design either zone plate or "megapinhole" [= sieve]

thank you Adam Stanislav whoever and wherever you are

Umm, andrew, where have you been??? ;)

Andrew
06-11-2007, 06:06 AM
Umm, andrew, where have you been??? ;)

seriously... I've been punching tiny wee little baby holes into brass shim by hand !!! ;D

earlj
06-11-2007, 10:41 PM
I have been reading up on photon sieves as used by the silicon chip folks for very fine x-ray lithography. The literature indicates that a random arrangement of pinholes centered on the bright rings of a zone plate can yield resolution that is better than the diameter of the biggest pinhole. The holes can be bigger in diameter than the width of the zone plate ring on which they are centered.

The problem is that the articles do not give you quite enough information to write the program to generate the photon sieve, The other problem is that I have no idea if this works with a spread of wavelengths of light. I am tempted to make a big zone plate on paper and then apply dots by hand and then shoot it on my tech pan and see what happens.

Check out this link and tell me what you think:

http://nanoweb.mit.edu/zpal/JournalArticles/photon_sieve.PDF