The notion of color spaces - or colorimetric spaces - is very important in color management. The most important color space is the one of your images. The famous Photoshop working space is often presented as being very important too, but really only in one particular case : the one where your image does not have an ICC profile when opened in Photoshop ! Let's see it now... A color space is a set of colors also called gamut. The gamut of a screen or video monitor represents all the colors they are able to display. The one of a printer, all the colors it is capable of printing. There are two types of color spaces : those related to each device (and we then speak of ICC profile) and some invented by researchers so that they do not depend on a device and the best known are the sRGB, Adobe RGB or ProPhoto in the world of photography and DCI-P3 or Rec 709 in the world of video. The largest of them represents the set of colours that a human being sees and is called the L*a*b* space. The L*a*b* color space is therefore the hub, the 'Gold' standard, for color management. All the other spaces are smaller because the technical limits do not allow the different devices we use to reproduce, for the moment, as many (saturated) colors. But why did we invent so many of them ?![]()
AdobeRGB is a color space introduced in 1998 by Adobe Systems Inc. AdobeRGB has a wider range of color reproduction areas such as green and blue. Adobe RGB provides 35% bigger in space than sRGB but both can display 16.7 million colors. Adobe Ps can now able to store image data, according to the. ProPhoto RGB is a newer color space that has a much wider gamut than Adobe RGB and is more in line with modern digital cameras. Adobe RGB 1998 features a wide gamut and compatibility with many.
Colorimetric modelsA color space therefore represents a set of colors 'visible' by a human being or device. This color set is also called gamut. There are several colorimetric models or colorimetric spaces: RGB, CMYK, L*a*b* or CIE xyz and in RGB, there are several variants encompassing more or less highly saturated colors (sRGB, Adobe RGB, ProPhoto in photo and DCI-P3 or Rec 709 in video, etc.) Some models are said to be peripheral dependent and are then called ICC profiles and others that they are independent and called color spaces. Finally, some are called working spaces. Why ? Which one to choose in photo editing or video editing software ? In his camera or his video camera ? From which point can we digitally represent a single color - absolute -, that perceived by a standard human eye, to answer the questions asked above ? The starting point : the CIE xyz space and the L*a*b* spaceColors are nuanced in about eight million different shades for an 'average' (but efficient !) eye. The CIE (Internationale Commission on Illumination) and mathematicians needed to represent them mathematically on a three-dimensional graph (in volume), two of which appear in the figure below (in plan). You may be familiar with the figures below : the chromacité diagram (left) and the L*a*b* space (right). They represent the colors visible to the human being but in two different ways and will therefore serve all the time afterwards. Should I Use Srgb Or Adobe RgbHere's aother question that is often asked! Any photographer know nowadays that there are several color working space, more or less broad. But how to choose between them? Is the small sRGB really that small and can't it be OK in certain situations? It has a 'bad' reputation but is it still accurate? Do we still need to use the very broad ProPhoto? What is the risk if you make a mistake? Are there really colors that can't be printed? Etc.
So many criteria come into line. Moreover, especially at the beginning of my 'practical experiments', I often had this thought: theoretically there should be a huge difference and yet, frankly, differences are not always that big really. Why? You should understand better why I like ProPhoto very much, but also why I defend sRGB by reading this page... It is by knowing well the differences between color spaces, from 'small' sRGB to 'broad' ProPhoto that you'll make the right choice. And you'll see that even if the smaller one does less, less is often enough! For more experienced users, we'll also see a few points that enable to optimize your choice. Then, I'll show you concretely how to choose in four practical examples... Let's start by putting an end to a strange belief about sRGB...Because of a mistake in profile assignment at the opening of a photo, I often hear that with sRGB profile colors are dull!!! That sRGB is not so great. That it confirms the reputation of this color space. While it's just a technical mistake! Let's see that in details. Little reminder because it doesn't go without saying!Prophoto Rgb Vs SrgbTo be displayed in Photoshop, a photo has to have an ICC profile. We've seen it in the previous page, choosing your working space in Photoshop . It's the ICC profile that will give it its 'true' colors. (I recommend you to read my page about profile assignment for further details. Indeed, an RGB value never represents a color (hence L*a*b*) theoretically. It is the color space or the ICC profile assigned that will give a colorimetric 'meaning' to an RGB value. So for a same RGB value (say 0, 255, 0), I won't get the same green (L*a*b*) in sRGB or in Adobe RGB: Comments are closed.
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December 2020
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