DrSlony at 21:23, 9 December 2019

2019-12-09T21:23:22Z

← Older revision		Revision as of 21:23, 9 December 2019
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			<div class="pagetitle">RGB and Lab*</div>

	[[File:RGB Cube Show lowgamma cutout b.png\|thumb\|RGB cube.]]		[[File:RGB Cube Show lowgamma cutout b.png\|thumb\|RGB cube.]]
	[[File:Lab color space.png\|thumb\|Lab color space.]]		[[File:Lab color space.png\|thumb\|Lab color space.]]

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2014-03-25T08:07:10Z

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[[File:RGB Cube Show lowgamma cutout b.png|thumb|RGB cube.]]
[[File:Lab color space.png|thumb|Lab color space.]]
''[https://en.wikipedia.org/wiki/RGB_color_space RGB]'' and ''[https://en.wikipedia.org/wiki/Lab_color_space CIE L*a*b*]'' (or just "''Lab''") are two different [https://en.wikipedia.org/wiki/Color_space color spaces], or ways of describing colors.

Many people wonder what the differences are between adjusting lightness, contrast and saturation in the RGB color space, or lightness, contrast and chromaticity in the Lab color space. RGB operates on three channels: red, green and blue. Lab is a conversion of the same information to a lightness component L*, and two color components - a* and b*. Lightness is kept separate from color, so that you can adjust one without affecting the other. "Lightness" is designed to approximate human vision, which is very sensitive to green but less to blue. If you brighten in Lab space, the result will often look more correct to the eye, color-wise. In general we can say that when using positive values for the saturation slider in Lab space, the colors come out more 'fresh', while using the same amount of saturation in RGB makes colors look 'warmer'.

<div align="center">
<gallery caption="Comparison of RGB and Lab adjustments">
File:colorspace_flowers_900_1_neutral.jpg | Neutral
File:colorspace_flowers_900_2_rgb_lightness.jpg | RGB Lightness +30
File:colorspace_flowers_900_3_lab_lightness.jpg | Lab Lightness +30
File:colorspace_flowers_900_4_rgb_contrast.jpg | RGB Contrast +45
File:colorspace_flowers_900_5_lab_contrast.jpg | Lab Contrast +45
File:colorspace_flowers_900_6_rgb_saturation.jpg | RGB Saturation +25
File:colorspace_flowers_900_7_lab_chromaticity.jpg | Lab Chromaticity +25
File:colorspace_flowers_900_8_vibrance.jpg | Vibrance +25
</gallery>
</div>

The difference between the ''Lightness'' slider in the ''[[Exposure]]'' section (in RGB space) and the ''Lightness'' slider in the ''[[Lab Adjustments|Lab]]'' section is subtle. A RGB ''Lightness'' setting of +30 produces an image that is overall a bit brighter than when using a Lab ''Lightness'' setting of +30. The colors in Lab ''Lightness'' are somewhat more saturated. The contrary is true for the Contrast sliders; when using a RGB ''Contrast'' of +45 the colors will be clearly warmer than when using a Lab ''Contrast'' of +45. The contrast itself is about the same with the two settings. Do not hesitate to use both sliders to adjust saturation and/or contrast. As for the ''Saturation''/''Chromaticity'' sliders, setting the RGB ''Saturation'' slider to -100 renders a black and white image which appears to have a red filter applied, while the Lab ''Chromaticity'' slider renders a more neutral black and white image. Positive RGB ''Saturation'' values will lead to hue shifts (the larger the value, the more visible the shift), while positive Lab ''Chromaticity'' values will boost colors while keeping their hues correct, rendering a crisp and clean result. Lab chromaticity (via the "''Chromaticity''" slider or "''CC''" curve) is the recommended method for boosting colors.

RGB and Lab - Revision history

DrSlony at 21:23, 9 December 2019

DrSlony: Added gallery