Author Archives: John Widdall

Noise in Digital Camera Raw Files – How to Measure it

After writing two articles on the Nature of Light and its relevance to digital photography, I found that the subject of noise still fascinated me and decided that I had to make some measurements. Looking at the wiggly waveforms of … Continue reading

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Test Cards for Monitor Adjustment – Revised

Calibration and Profiling I have updated the page on this subject in order to clarify the distinction between calibration and profiling (or characterisation), and to remove reference to commercial operating systems now obsolete. To avoid confusion I have now included … Continue reading

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How the Nature of Light affects the performance of digital cameras — (Part 2) Noise

In the second of two articles I look at another natural phenomenon, photon noise (also known as Shot noise). As with diffraction blur, the problem becomes more serious as the physical size of the sensor is reduced. Whilst this is … Continue reading

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How the Nature of Light affects the performance of digital cameras — A new Technical Note

Reducing the physical size of a camera, even if the total number of pixels is maintained, inevitably reduces the quality of the images because of two fundamental properties of light itself. This technical article looks at diffraction, usually explained by … Continue reading

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Test Cards for Monitor Adjustment – An Update

Basic adjustment of monitors and projection systems When I last updated my page on this subject (2012) I decided that it was best to offer the test cards as .png files and leave it to the user to assign a … Continue reading

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Raw Processors: Which Demosaicing Method? (Part 2)

Further Thoughts on Demosaicing Methods in Free Open Source Raw Processors I suggested in Part 1 that I would also compare the performance of different demosaicing methods on noisy images. I now believe that this would be impractical as any … Continue reading

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Raw Processors: Which Demosaicing Method? (Part1)

Comparison of Demosaicing Methods available in Free, Open Source Raw Processors My previous article included a table listing the various demosaicing algorithms offered by the four raw processors considered and I wondered why we (as users) needed such a wide … Continue reading

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