Focal Stack Compositing for Depth of Field Control

Many cameras provide insufficient control over depth of field. Some have a fixed aperture; others have a variable aperture that is either too small or too large to produce the desired amount of blur. To overcome this limitation, one can capture a focal stack, which is a collection of images each focused at a different depth, then combine these slices to form a single composite that exhibits the desired depth of field. In this paper, we present a theory of focal stack compositing, and algorithms for computing images with extended depth of field, shallower depth of field than the lens aperture naturally provides, or even freeform (non-physical) depth of field. We show that while these composites are subject to halo artifacts, there is a principled methodology for avoiding these artifacts—by feathering a slice selection map according to certain rules before computing the composite image. CR Categories: I.4.3 [Image Processing and Computer Vision]: Enhancement—Geometric correction; I.3.3 [Computer Graphics]: Picture/Image Generation—Display algorithms