Author Topic: Gamma 2,2 today  (Read 3251 times)

2020-06-04, 03:34:18

n2graf

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There's a thing I dont understand.

Wy are we applying sRGB with gamma 0,45 to mach the 2,2 gamma of the monitor and get a lineal image? This made sense when monitors were CRT and reduced gamma, but LED displays have already been invented and there is no need to reduce the gamma of current monitors. Why do they keep reducing it?


2020-06-04, 15:12:22
Reply #1

maru

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I have no idea who exactly does that, and why anyone would ever want to.

The only use case I can think of is converting a gamma 2.2 image into gamma 1.0, for example in case you render a grayscale displacement map and save it with wrong settings.
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2020-06-04, 17:00:19
Reply #2

n2graf

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Everyone does that XD sRGB includes the 0,45 gamma for default, and all the pictures include sRGB profile embed or applyed in the pixels (you only not use gamma 0.45 when you are in a RAW file like EXR) And everyone have his monitors configured with 2.2 gamma for default, for that reason you have to mach it on 3dsmax (that it have it for default too).

2020-06-04, 17:27:31
Reply #3

maru

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Everyone does that XD sRGB includes the 0,45 gamma for default

Where did you find this information? I am pretty sure sRGB uses sRGB gamma ;)

Quote
Unlike most other RGB color spaces, the sRGB gamma cannot be expressed as a single numerical value. The overall gamma is approximately 2.2, consisting of a linear (gamma 1.0) section near black, and a non-linear section elsewhere involving a 2.4 exponent and a gamma (slope of log output versus log input) changing from 1.0 through about 2.3. The purpose of the linear section is so the curve does not have an infinite slope at zero, which could cause numerical problems.
Source: https://en.wikipedia.org/wiki/SRGB
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2020-06-04, 17:40:56
Reply #4

n2graf

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Sorry i mean the photographic cams, that applyes sRGB own gamma in 0,45. It's that because it have to mach with the usual 2.2 gamma of the displays and get the linear result. If sRGB were any other way, you would see an image resoult so brighter or draker.
« Last Edit: 2020-06-04, 17:48:18 by n2graf »

2020-06-05, 09:27:53
Reply #5

Ondra

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Matching the monitor gamma was done back in Windows 95 times. Today we still use the same gamma, but for other reasons. GPU/monitor adjusts the colors to its specific output curve, but it still expects to receive the input data with gamma 2.2 when sRGB is used. You will get the same result displayed no matter what the physical properties of the display are, if you provide the input data in correct format (which for sRGB includes gamma 2.2). It is a data exchange format now.
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