Re: Zone plates for a body cap

On Friday, October 25, 2002, at 04:21 PM, Guillermo wrote:

>
> ----- Original Message -----
> From: "Guillermo" <penate@rogers.com>
>>
>> I gather that by "aperture of the zone plate" you mean the size of
>> each of
>> the rings. Mr.Pinhole formula is what the scientific community uses
>> for
>> their high-tech uses of zone plates and my non-scientific tests
>> (focusing
>> aerial images produced by zoneplates) have confirmed that. Other use
>> slightly different formulas.
>
> I was reading my own post and it seems not to be too clear.
>
> What I meant was that when I mount zone plates on my 4x5 view camera
> and
> focus on the aerial image until it is a "sharp" as they would be, the
> distance zone plate to film plane matches very closely with what the
> formula
> Radius = SQRT(wave length x focal length x ring#) would predict.
>
> Now, the formula can also be written as Diameter = 2 x SQRT(wave
> length x
> focal length x ring#). Some people use formulas slightly diferent,
> what
> they change is that number "2", Patton for instance, uses 1.86
> http://www.stanford.edu/~cpatton/zoneplatemath.htm
>
> Guillermo
>
>
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Hi-

The goal is to calculate f number of the zone plate, for a first
approximation of the exposure. So it sounds like the formula will work.
All I have to do is keep radius and diameter straight.

Thanks for your help
Beaker
Received on Sat Oct 26 09:02:08 2002