Imagery: Auto - Large Table of Contents

EXCERPT page containing first few paragraphs. 2022-08-17 00:42:38

Bits, Signal and Noise

With digital images, dark tones are represented with very few values. With a digital sensor, there is measurement error called noise. The digital sensor noise is always of low numeric values— hence the errors (noise) show up in the dark tones. Noise increases and creeps up into the mid-tones with higher ISO (as the sensor readout is more amplified).

As a simple example, a pixel that should read as pure black (a value of zero) might actually measure at 0, 1, 5, 8 13 or 20 (or whatever). A pixel that should measure at 17 might read out at 7, 13, 17, 23 or whatever. This error is random by pixel, but in practice there can be streaks/banding and/or grid-like patterns (particularly ugly). Colored speckles and a color cast are typical, as well as brightness variation. It gets worse at higher ISO values.

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  • Eases into photographic challenges with an introductory section.
  • Covers aspects of digital sensor technology that relate to getting the best image quality.
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  • Optical aberrations: what they are, what they look like, and what to do about them.
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  • Optical aberrations: what they are, what they look like, and what to do about them.
  • How to test a lens for a “bad sample”.

Intrigued? See Focusing Zeiss DSLR Lenses For Peak Performance, PART ONE: The Challenges, or (one topic of many) field curvature.

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