> Gordon -
>
> Like a pinhole, the Zone Plate would be created for a specific focal length.
>
> The center does need to be opaque, which then dictates the clear/opaque areas
> of the surrounding rings.
>
> You can reference the excellent article, The Zone Plate by Chris Patton, at
> http://members.home.net/hmpi/Pinhole/Articles/PinholeArticles.htm for more
> information.
>
> Cheers -
>
> george
I don't think the center needs to be opaque, just that every other
zone is blocked out. If you use Chris Pattons original pattern, it has
a dark center which gives you a clear center when you copy it on to
negative film like Tech Pan.
