Wednesday 10 June 2015

Forensics - Maximising Image Sharpness

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.

Focus is one of the parameters used in the Image Quality Tool.  HERE I have it summarised.  

Clearly the resolution of the sensor has a function in image sharpness as detailed HERE.  Acutance is the impression of sharpness created by contrast.

Creation of a full colour image from a RAW Bayer image involves interpolation which reduces the overall sharpness of the image as discussed HERE.

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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