There are a number of different factors influencing image sharpness. I have covered various aspects of image sharpness in a few postings in the blog but I haven't pulled them all together in one place.
IMAGE FOCUS
Focus is one of the parameters used in the Image Quality Tool. HERE I have it summarised.
PIXEL RESOLUTION AND ACUTANCE
Clearly the resolution of the sensor has a function in image sharpness as detailed HERE. Acutance is the impression of sharpness created by contrast.
RAW IMAGE FORMATION
Creation of a full colour image from a RAW Bayer image involves interpolation which reduces the overall sharpness of the image as discussed HERE.
AIRY DISC
I discussed the concept of an Airy disc HERE. If we consider the focus of a discrete point of light by a lens, an Airy disc is considered the sharpest possible image by an ideal lens.
Putting all these concepts together makes for a rather complex subject matter but the experts at Cambridge in Colour have produced another excellent tutorial entitled Lens Diffraction & Photography which takes these and other related parameters and provide what is effectively a guide to obtaining the sharpest possible images from our camera equipment. Part 2 of the tutorial can be found HERE. Perhaps the most interesting concepts are the distinction between Artefact-free and Extinction Resolutions and also the fact that higher aperture can result in lower image sharpness (diffraction limit).
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