Pentax dynamic range tests up on DPR

Started Sep 7, 2012 | Discussions thread
dosdan Contributing Member • Posts: 503
Re: Pentax dynamic range tests up on DPR

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.


" 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. "

" 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 "


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