1. An apparatus for depth of field rendering on captured images to simulate an out-of-focus effect as would arise in response to using a larger aperture, comprising: an imaging element having an aperture with a physical aperture size, and configured for capturing digital images at a focus setting; a computer processor, associated with a memory, coupled to said imaging element and configured for processing the digital images received from said imaging element; and programming executable on said computer processor for, capturing at least a pair of images at a focus position which differs between said pair of images while using an identical aperture setting, dividing said pair of images into subimage blocks, determining a blur difference between subimage blocks of said pair of images based on a matching curve for said imaging element as a relationship between iteration number and the focus position, determining a defocus blur between subimage blocks of said pair of images, and blurring subimage blocks of said pair of images by a number of convolutions with a blur kernel in response to the blur difference determined between said pair of images to generate a resultant image simulating utilization of the larger aperture.