![]() ![]() And as with bokeh in a lens, this affects the image even in non-highlight areas -Īreas of bright light have a, well, diffused glow around them. Point sources of light will actually show the concentric-circle pattern of the zone plate in a very dramatic way. Perhaps most importantly, the zone plate look is quite distinctive. (On my Pentax K-7, the metering even works accurately.) The Look And, although it'll be dark, you can even compose through the viewfinder. This means that with a modern SLR, you can, with care, shoot hand-held. For example, Lensbaby's (out of production, as of 2015) Pinhole/Zone Plate optic provides an f/177-equivalent pinhole, and in zone plate mode is something like f/19 - 6½ stops faster. Second, the amount of light let through is significantly greater. (This same sort of image is also used, for unrelated reasons, and with finer circles than the one above, to produce moiré patterns for testing display quality, or for tuning autofocus.) Versus Pinhole LensĪ zone plate is often compared to a pinhole lens, but there are important differences.įirst, it does have a depth of field and therefore can be focused, although usually the DoF is rather large (like using a 35mm lens stopped down to f/22 or so). Graphic by Tom Murphy VII, licensed CC-BY-SA And the Wikipedia article on zone plates has some graphics, one of which I'm borrowing here: The D.I.Y zone plate web page Whiz Kid Technomagic Zone Plate Designer explains the math and pratical physics behind the choice of size and spacing quite nicely. In order to create a focused image, these are placed so that the interference creates zones of "constructive" interference, forming a focused image. The plate, which is a small piece of glass, plastic, or something else relatively transparent, is inscribed with concentric opaque circles. If you're attracted to a certain lo-fi "old-camera" aesthetic, using a zone plate is a way to get it authentically, rather than faking it in post-processing. And it's cool from a photography point of view, because the images produced have a unique glow, with an impressionistic almost-painted look. ![]() This is cool from a theoretical point of view, because it demonstrates the wave nature of light. A zone plate is a way of focusing light, like a lens, but using Fresnel diffraction instead of refraction. ![]()
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