Credible repair of Sony main-sensor PDAF striping artifacts

Since the introduction of the Minolta Maxxum 9000 in 1985, PDAF (phase detect automatic focus) has been the standard way to achieve sharply-focused images of fast-moving action, such as professional sports. In a typical SLR (single lens reflex) camera, the image for the optical viewfinder is reflected up by the main mirror, while a secondary mirror and optics copy the image to the PDAF detector. However, such an arrangement is impractical for mirrorless digital cameras. Thus, there have been a variety of methods used to incorporate phase sensing on the main sensor - with various trade-offs. The current work discusses some of these trade-offs and then describes in detail a specific type of striping artifact introduced by the masked pixel structures used in Sony sensors. A computational method for credible repair of this artifact also is presented. The method described is quick and fully automatic; it has been implemented as KARWY-SR, an open source JavaScript version using a drag-and-drop interface to repair the artifact in Sony ARW raw files.