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


November 11, 2011


Henry Gordon Dietz


University of Kentucky


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.


Henry Gordon Dietz

Upon completing his Ph.D. at Polytechnic University (now NYU-Poly) in 1986, Henry G. (Hank) Dietz joined the Computer Engineering faculty at Purdue University’s School of Electrical and Computer Engineering. In 1999, he moved to the University of Kentucky, where he is a Professor of Electrical and Computer Engineering and the James F. Hardymon Chair in Networking. Despite approximately 200 scholarly publications mostly in the fields of compilers and parallel processing, he is perhaps best known for his research group’s more practical research products, including: barrier synchronization hardware, PCCTS/Antlr compiler tools, world’s first Linux PC cluster supercomputer and the Parallel Processing HOWTO, SWAR (SIMD Within a Register), FNNs (computer-evolved Flat Neighborhood Networks), MOG (MIMD On GPU), and single-shot Anaglyph capture. Much of his work is freely distributed via the Aggregate.Org research consortium, which he leads. Dietz also is an active teacher, and was one of the founders of the EPICS (Engineering Projects In Community Service) program. He is a member of both ACM and IEEE.