• Paolo Ferraris

What is a Color Space?

Color space and color gamut are two of the most confusing, most complicated and least important concepts when it comes to making decisions about the way you shoot. This quick post is aimed at giving you some basic knowledge about these two concepts so you can rapidly move on and start taking pictures in the real world with the right color space camera setting.

Color Space & Color Gamut. https://commons.wikimedia.org/w/index.php?curid=8359333

LAB (or CIELAB) Color Space


A color space is a specific organization of colors. It is a mathematical model describing how colors can be represented as a combination of numbers. In other words, a color space is a method to describe numerically all possible shades of colors.


The main color space, the standard when it comes to describing colors, is the LAB. The LAB space encompasses all colors the human eye can see and it is device-independent, meaning it is not affected by the technical properties of the device used to record or to display colors. The LAB color space expresses color as three values: L, A and B. L stands for lightness and it goes from black (0) to white (100), A is a point in the color space on the axis from green to red, and B is a point in the color space on the axis from blue to yellow. These 3 numbers give us a visual point with a specific color at a specific light intensity.


All color spaces have a particular point, called white point, where no specific hue has predominance. It is a point defined as color-neutral. According to the light intensity, it can go from black to pure white, crossing all shades of gray.


To define, to set a white point is essential in every color space that is device dependent because it becomes a benchmark, a frame of reference for the device. All colors in the color space used by cameras are a combination of 3 primary, basic colors (RGB), because each pixel in the camera’s sensor is made of 3 tiny receptors, each sensitive to the spectrum of one specific color (RGB.)


All colors in a color space are related to each other and moving the white point changes the representation of all other colors in the image. In a future post, we'll see why it is so important to find the white point, the white balance on your camera and how it is done.


What is color gamut? Color gamut is a particular complete subset of colors. Whereas the LAB color mode is device independent and it encompasses all colors visible to the human eye, the color spaces used by cameras are device-dependent and always smaller than the LAB mode. Device dependent color spaces deal with the technical limitations of devices used for recording color (cameras) and devices used to display color (Monitors, TVs.)


The concept of Color Gamut is very similar to the concept of Dynamic Range. Whereas Dynamic range refers to light intensity and to the capability of the camera to capture both dark and bright areas in the same image, Color gamut refers to all the subsets, all the combinations of colors that a camera can record or an output device like a computer monitor or a TV set can reproduce. The LAB color space has the widest gamut. Color spaces used by cameras always have a smaller gamut and are contained inside, within the LAB space.


sRGB Color Space. Color space photoshop.


Color spaces are mathematical systems our cameras use to organize and describe colors. Color spaces used by our cameras are additive color spaces. They are called additive because the color our camera records in a pixel is obtained by adding and mixing the signal from the three primary colors receptors in the sensor at different intensity levels. Regardless of the model or the brand, the color space your camera uses is some form of RGB space.


A particular RGB color space is defined by the three chromaticities of the red, green, and blue additive primaries, and can produce any chromaticity that is in the triangle defined by those primary colors.


The 3 primary colors in additive systems are the ingredients and every color, any shade, any hue is a specific combination of these 3 ingredients. Every color we see is the sum, the addition of a certain quantity of Red, a certain quantity of Green and a certain quantity of Blue.


One of the most commonly used color spaces is the sRGB (standard Red Green Blue,) an RGB color space that Hewlett Packard and Microsoft created in 1996 to use on monitors, printers, and the Web. When we talk about our cameras or our viewing devices, like a computer monitor, this RGB color space represents all the color combinations that can be recorded or displayed. The sRGB space encompasses only a portion, a smaller part of the LAB space.


Adobe RGB 1998 Color Space


Here you have a graph of the Adobe RGB color space.


Adobe RGB vs sRGB. https://commons.wikimedia.org/w/index.php?curid=29994804

As you can see, it is still an RGB space. On the tips of the triangle that represents the color gamut of the color space, you can notice the three primary colors, red, green and blue. We have a white point in this color space too and again, this color space is a subset of the LAB color space.


So what's the difference between the two color spaces: sRGB and Adobe RGB?


This graph illustrates the comparison between several color spaces, inside the main, the standard LAB space, here defined as the horseshoe shape of visible color.


You can notice how the Adobe RGB has a wider color gamut compared to the sRGB. The base of the triangle is the same but the Adobe RGB triangle is taller and covers a wider area on both sides of the sRGB one.


Wider color gamut means the Adobe RGB color space can record and display more combinations of color. The Adobe RGB color space encompasses approximately 50% of the visible colors specified by the LAB color space. The sRGB only 35%.


The Adobe RGB and the sRGB gamuts are often comparable in mid-tone values, but there are clear differences in the shadows and in the highlights. Adobe RGB expands its advantages to areas of intense orange, yellow, and magenta regions, on the right side of the smaller triangle. It also improves the gamut of the sRGB color space in cyan-green hues, on the left side of the triangle.


We can think of the Adobe RGB color space as an expansion of the sRGB space. The Adobe RGB is a color space with a larger gamut.


Color Space setting on your camera


We have learned in this post what a color space is. And we have seen on the chart why a wide color gamut is important.


A color space with a wider color gamut can describe and record a wider combination of hues, it can record and display chromaticities, sets of specific colors, that color spaces with smaller gamuts don't contain.


This is the reason why I suggest, as soon as you buy a new camera, to flip through the menus, find the setting about color space and if the standard, pre-set color space is sRGB to change it to Adobe RGB or to the space color with the widest color gamut allowed by your model.


#colorspace #colorgamut #photography #photographers

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