Re: Zone plates for a body cap

On Thursday, October 24, 2002, at 10:28 PM, Guillermo wrote:

>
> ----- Original Message -----
> From: "Beaker" <mbeacom@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!
Received on Thu Oct 24 23:24:11 2002