EXCERPT page containing first few paragraphs. 2024-04-18 16:16:00
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K3 Autofocus Accuracy
All cameras and lenses with phase detect autofocus (conventional autofocus) have factory tolerances for accuracy. With high resolution digital sensors, the tolerances must rise due to the extreme pixel density: the 24MP sensor in the Pentax K3 has a pixel density equal to a 56MP sensor on full frame.
One can fairly ask a simple question: if a brand-new camera and brand-new lens are acquired, shouldn’t the focus be close to perfect? Unfortunately the answer is generally “no”, because the factory tolerances are not particularly tight, and because a lens error and a camera error can be additive or subtractive; a small error plus another small error in the same direction mean an unacceptable result.
Phase detect autofocus errors tend to be more of a problem at fast (bright) apertures such as f/1.4, at near-infinity focusing distances, and with shorter focal length lenses. Telephoto lenses are usually better due to the shallow depth of field and (usually) higher contrast at full aperture, both of which help the camera to discriminate the best focus. The reverse holds for wide angle lenses, e.g., a 35mm f/1.4.
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Diglloyd DAP is DSLR-oriented, but also contains workflow and other topics. Much of the focus is on Canon and Nikon but also Pentax and Pentax medium format.
Special emphasis is placed on lens evaluation, focusing on Canon and Nikon and Sigma lenses, but with a few others like Rokinon/Samyang.
- Make better images by learning how to get the best results right away.
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ISO 100 + 0.5 push, Contrast +40, Highlights -40, Shadows +100
Pentax K3 + Pentax 70mm f/2.4 @ f/3.2