2011/06/25
plenoptic cameras and the meaning of photography
Raytrix introduced the R11 Lightfield Camera not too long ago. It is still low-res and expensive, but improved versions of these should eventually catch on — they make too much sense not to.
The idea of plenoptic cameras has been thrown around for quite a while. Instead of a conventional camera with a single lens focusing a single object plane onto the in-camera image plane (i.e. the sensor), a plenoptic camera attempts to capture enough additional information so as to be able to reconstruct “all possible” images that can be obtained from the light entering the same aperture. The most talked-about application is subsequent refocusing; if it were just this, then multi-capture with mechanical focal-length sweeps using a conventional camera would suffice. Another is stereograms, but again, two spaced shots would suffice for that. A plenoptic camera does more in one shot and makes these merely special post-processing cases. The simplest conception of a plenoptic camera is essentially an array of mini-cameras (microlens + micropixel array for each logical pixel) that separately captures light from all directions at each point in the image. In between conventional cameras and plenoptic cameras are perhaps smarter, sparser non-regular arrays like these coded aperture systems that hark back to old radio-astronomy literature. These have good signal processing properties from a deconvolution perspective, but the full-array plenoptic camera like the R11 seems fully general, and with some future industrial scaling, the saved expenses of a compromise may be inconsequential.
Fine, so a plenoptic camera may make clever use of its given aperture size, but do we really get something for nothing? To answer that, first a digression.
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