Topic: Zone Plate Question

[cpierce]

I have been wanting to play with a zone plate for one or more of my cameras and am trying to understand how to implement.   I was thinking of using a zone plate on a Mamyia 645 or a RZ just to see what kind of results.  I have read some things but still am a bit unsure of the correct size of plate, what material to make it out of or should I buy one and if so would I implement using a body cap....   Also wondering if the image is visible in the view finder.

Any real life experiences that may help me out?


Thanks
Chris

[Francois]

Though I've never used a zone plate, I do know a few things about them...
I highly recommend first putting your hands on the pinhole designer program (http://www.pinhole.cz/en/pinholedesigner/) since it has a nice zone plate calculator. It will even make a PDF for you to photograph if you plan on using the DIY route.
The small software will tell you all the info you need to know.

As for a visible image in the viewfinder, you most probably have a fairly bright one. When you play with the software, you realise fairly quickly that zone plates all have an f/stop that is pretty low (read wider aperture) when compared to a pinhole.

Using the software produced PDF, you can then photograph the printout on B&W film and process it for high contrast. Don't forget that you have to make sure the reproduction size matches the calculated dimensions or else it won't work! For that, I think the f/calc software has a panel that will do the math for you (http://tangentsoft.net/fcalc/)... but I haven't had it on my computer for years. All that is left to do is mount it in a drilled body cap...

But, for things like that, you might prefer to buy a ready made one just to save yourself the hassle and reproduction calculations. But at least you'll know what to look for when buying...

[Andrew]

I've made several "pseudo-sieves" where I tried to replicate a pinhole sieve [pretty similar to a zone plate] by making multipe small holes in brass shim.... these mostly ended up around f68 and an I trialed them on a 35mm slr with body cap and got a dim image that was enough to line up a shot so long as there wasn't too much background light. Afterwards, I picked the ones I liked the results from and mounted them on a roll film camera with no viewfinder.

here's another link to check out:
http://www.whizkidtech.redprince.net/zoneplate/
the calcuator will tell you expected f-stops and you'll probably find them about 1 stop slower than my hand mades?