PDA

View Full Version : help with whizkid zoneplate design site



murrayatuptowngallery
09-24-2007, 03:31 AM
Anyone know if it's possible to get a 1:1 image out of this site?

I'm getting confused.

I'm looking at trying a Zone Plate for a camera obscura, around 8+/- 1 meter focal length.

This might be big enough to hand carve with an exacto blade or make a transparency onto glass...

Thanks

Andrew
09-24-2007, 06:17 AM
As far as I can see, you design the plate and then download a final high res image.... if you want it 1:1 you'll have to use a graphics program to resize it.

and for something as huge as you're after, you'll have to select the "size" option to be large or extra-large or you'll have the edges clipped off the image you download

gneissgirl
09-26-2007, 01:21 PM
Andrew's right. As I recall (haven't been to this site in a while) the idea is to download the image and resize it to whatever size you can conveniently print out with your device and get good resolution. Then you photograph your printed zone plate to produce the image size you want on the film. So, that depends on the focal length of the lens you're using, the distance of the image to the lens, etc. It really doesn't matter what size the downloaded image is, but you do have to resize it in a graphics program, print it to known dimensions, and do the simple calculations to determine the distance from print to lens to get the film image the right size. Clear as mud?

How big is the opening in which the ZP will be placed? If it's a few inches, then you might well be able to print one out at high enough resolution directly on transparency material, or make a contact print on film. For most regular cameras, the final ZP has to have a pretty small diameter (a few mm) and there's no way most home printers can do that well enough.

murrayatuptowngallery
09-26-2007, 11:14 PM
OK, thanks.

I thought each plate software run explains the actual diameter, but the output is so verbose I wanted to ask & really scrutinize it better.

If the actual size is stated, then no problem messing with resizing in s/w.

Thanks

Murray

Andrew
09-27-2007, 05:40 AM
yeah it definitely specifies the file dimension and final printout size

I just "made" a file and the page which is displayed contains a small preview image of the zoneplate and the link to the download...
this page says:

"About this zone plate
It is a PNG bitmap (2011x2011 pixels) with a 2540/20 representation of the zone plate.
That means that it either needs to be rendered digitally (printed to film or on a transparency) at 2540 DPI, or photographed, to produce an image contained inside a black square box 20 mm high and just as wide."

obviously the detail will be different for other zoneplates you might think up

ednaz
10-02-2007, 12:48 PM
Nice to know it's not just me. I've done a few zone plates of various sorts on the site and couldn't figure out what I'd gotten, particularly after printing a couple out with the intention of photographing them. Got weird, ugly, mis-shapen things.

If math didn't make me itch so much, I might have more success experimenting with pinholes.