Pentax dynamic range tests up on DPR

Started Sep 7, 2012 | Discussions thread
dosdan
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Re: Pentax dynamic range tests up on DPR
In reply to sweetpapa, Sep 7, 2012

sweetpapa wrote:

Shooting RAW, dynamic range should be 14 EV instead of the 8 with JPEG.

A colourspace, TRC & gamma correction is applied to the linear raw image that is developed either in-camera or in software and then saved as a JPEG/TIFF.

Since the encoding is non-linear (with the non-linear response of the eye, missing brightness steps at high levels are not noticed) the DR that a 8-bit JPEG with an sRGB TRC can hold according to GordonBGood, is 11.7 stops. Other TRCs can hold a greater DR, e.g. Adobe RGB with gamma=2.2 can hold over 17 stops of DR.

See:
http://forums.dpreview.com/forums/read.asp?forum=1018&message=25074654

http://forums.dpreview.com/forums/read.asp?forum=1036&message=36849343

http://en.wikipedia.org/wiki/Tone_response_curve

http://en.wikipedia.org/wiki/Gamma_correction

" In any case, binary data in still image files (as JPEG) are explicitly encoded (that is, they carry gamma-encoded values, not linear intensities) "
...

" almost all standard RGB color spaces and file formats use a non-linear encoding (a gamma compression) of the intended intensities of the primary colors of the photographic reproduction; in addition, the intended reproduction is almost always nonlinearly related to the measured scene intensities, via a tone reproduction nonlinearity. "

http://en.wikipedia.org/wiki/Jpeg

" Many JPEG files embed an ICC color profile (color space). Commonly used color profiles include sRGB and Adobe RGB. Because these color spaces use a non-linear transformation, the dynamic range of an 8-bit JPEG file is about 11 stops "

Dan.

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