https://en.wikipedia.org/wiki/Bit_depth

https://en.wikipedia.org/wiki/Audio_bit_depth

https://en.wikipedia.org/wiki/Color_depth


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Note added at 3 hrs (2018-01-20 07:04:03 GMT)
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https://en.wikipedia.org/wiki/Audio_bit_depth

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In digital audio using pulse-code modulation (PCM), bit depth is the number of bits of information in each sample, and it directly corresponds to the resolution of each sample. Examples of bit depth include Compact Disc Digital Audio, which uses 16 bits per sample, and DVD-Audio and Blu-ray Disc which can support up to 24 bits per sample.

In basic implementations, variations in bit depth primarily affect the noise level from quantization error—thus the signal-to-noise ratio (SNR) and dynamic range. However, techniques such as dithering, noise shaping and oversampling mitigate these effects without changing the bit depth. Bit depth also affects bit rate and file size.

Bit depth is only meaningful in reference to a PCM digital signal. Non-PCM formats, such as lossy compression formats, do not have associated bit depths.[note 1]

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Note added at 3 hrs (2018-01-20 07:07:07 GMT)
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Noise, Dynamic Range and Bit Depth in Digital SLRs
http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/

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Noise, Dynamic Range, and Bit Depth:

Both Canon and Nikon have introduced a finer level quantization of the sensor signal in digitizing and recording the raw data, passing from 12-bit tonal gradation in older models to 14-bit tonal depth in newer models. A priori, one might expect this transition to bring an improvement in image quality -- after all, doesn't 14-bit data have over four times the levels (16384) compared to 12-bit data (4096)? It would seem obvious that 14-bit tonal depth would allow for smoother tonal transitions, and perhaps less possibility of posterization. Well, those expectations are unmet, and the culprit is noise.

In the absence of noise, the quantization of an analog signal introduces an error, as analog values are rounded off to a nearby digitized value in the ADC. In images, this quantization error can result in so-called posterization as nearby pixel values are all rounded to the same digitized value. An example is shown in Figure 16; here, an 8-bit grayscale image of a smooth tonal gradient was generated in Photoshop using the gradient tool. The bit depth was then truncated to five bits (32 tonal levels instead of 256) using two successive levels adjustment layers, the first one reducing the output range from 0-31 from an input range of 0-255, the one above it setting the input range to 0-31 and the output range from 0-255. Mouse over the gradient to see the posterization that results from bit depth truncation.

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Note added at 3 hrs (2018-01-20 07:10:20 GMT)
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Bit depth (audio) - Glossary - Federal Agencies Digitization Guidelines Initiative
http://www.digitizationguidelines.gov/term.php?term=bitdepth...

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Term: Bit depth (audio)
Definition:
Bit depth (aka "word length") fixes the encoded dynamic range of an audio event or item. 24-bit audio provides a dynamic range that approaches the limits of the dynamic ranges of sound encountered in nature; in contrast, 16-bit audio, the CD standard, may be inadequate for many types of material especially where high level transients are encoded, such as the transfer of damaged discs. When reformatting, the International Association of Sound and Audiovisual Archives (IASA) recommends a bit depth of at least 24 in order to ensure that the transfer process captures the full dynamic range.

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