Repairing Focus Blur
In principle, sharpening can be put into three categories (though the practice may be different). The first is sharpening to overcome softness introduced during capture, of which there are two components: optical softness from the lens, and digital softness from the sensor.
Most lenses show soft spots in different parts of the images area and at different apertures. The sensor and the processing of the signal it captures also introduces softness when continuous tones are translated into pixels on a regular sampling grid, and details that are finer than the sampling frequency are averaged by interpolation. The second category is sharpening for creative or repair reasons, applied to details identified by the photographer. The ...
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