On Thursday, October 24, 2002, at 10:28 PM, Guillermo wrote:
----- Original Message -----
From: "Beaker" <mbea...@mac.com>
I'm thinking of getting a sheet of Zone Plates made for a Pentax K
mount body cap (optimized for 43 mm). Would anyone be interested in
buying any? The reason I ask, the negative will cost something like
$50
to $75, (the shop has a $50 minimum.) and I would like to spread the
cost out a little. For a little more to cover the cost of a body cap,
I
could send out the finished article. The negative isn't made yet- I'm
just trying to gauge the interest, so the price is still "to be
determined".
A sheet made by an image setter can fit lots of ZPs, you don't have to
have
the whole sheet full of 43mm ZPs, I would suggest you make some other
focal
lengths as well. 65mm for instance is perfect for attaching it to the
back
of the shutter of a Lubitel. Another possibility, which is not
mutually
exclusive with the one previously mentioned, is to make similar focal
lengths ZPs but with different number of rings, which will give you
different f/stops, I.E., a 43mm ZP with 9 total rings is f/64 (aprox)
but a
19 rings one is f/45 and would probably have more of that ghostly
effect.
I make my own ZPs using lith film, otherwise I'd be joining you,
nevertheless I recognize this as a good chance for those that have not
experimented zoneplate photography to try it with very minimum
investment
and help you share the cost in the process, a win/win scenario if you
ask
me.
Good luck.
Guillermo
All Good points- thanks! I was tinkering around with Mr. Pinhole's zone
plate generator, and had already made up smallish group of 43 mm, 7
ring (I think) zone plates. That is what I had in mind with the first
post. If there is any interest, I could just as well make up a group of
custom zone plates.
Guillermo- how do you figure out the aperture of a zone plate? Mr.
Pinhole mentions this formula: <radius = sqrt(wavelength *
focallength * ring)>. I was guessing that this would give a good number
to start with. Is this a good guess?
One last thing- I've never worked with zone plates before, or even have
litho negatives made, so we will learn together what works, and what
doesn't!
