On observing shape from defocused images

Accommodation cues are measurable properties of an image that are associated with a change of the geometry of the imaging device. To what extent can three-dimensional shape be reconstructed using accommodation cues alone? This question is fundamental to the problem of reconstructing "shape from focus" (SFF) and "shape from defocus" (SFD) for applications in microscopy, image restoration (de-blurring) and visualization. We address it by studying the observability of accommodation cues in an analytical framework that is independent of the imaging device.