The Benefits Of Being Out Of Focus: Making the Most of Lens PSF

Speaker  Henry Gordon Dietz

Affiliation  University of Kentucky

Host  Andy Wilson

Duration  01:25:44

Date recorded  11 November 2011

The point spread function (PSF) of a lens describes the impulse response of that lens – how a point light source is imaged. It is commonly assumed that an out-of-focus (OOF) point's image will be blurred, but that is not what happens. This talk describes some of the things we have learned by studying the properties of OOF PSFs.

The work discussed in this talk began with the observation of minor defects in depthmaps created in-camera using C code for depth-from-focus within a Canon Powershot under CHDK. Understanding these flaws led to a two-year study of the OOF PSF of approximately 100 lenses and creation of a wide variety of new computational photography methods. One of the simplest involves the capture of anaglyph images using a trivial user-reversible modification to nearly any ordinary camera. These anaglyphs may be viewed in the usual way as stereo images, but they also can be reprocessed much like plenoptic images.

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