Color Basis of Photography Course (3): Color Space Commonly Used in Photography

This tutorial is the third in my photography tutorial series, which may be a bit professional and boring! But it's absolutely useful. I hope you like collecting and encourage my creation. I will continue to update the basic photography course.

Color is the different feelings of people's eyes to different frequencies of light. Colors are both objective (light with different frequencies) and subjective, that is to say, there are cognitive differences in colors, and people can distinguish more than 6.5438+million colors with the naked eye. In order to describe and use color qualitatively and quantitatively, people have established various color spaces.

First of all, when watching this tutorial, you should ask me why I should learn and understand color space. What's the use of color space for you?

In order to let you know the color space better, it is necessary for you to know the color model first, because the establishment of color space is based on the color model.

The concept of color model:

Color model is a mathematical model that arranges colors into a set of numerical values according to rules in order to describe and use colors scientifically and quantitatively. For example, the RGB model uses three values of RGB to describe colors. Generally, color models are divided into two categories: device-related and device-independent.

The concept of color space:

Colorspace, also called "color gamut", is used to represent the color range defined by the coordinate system of a color in the color model, and to represent the shape and size of a color image in the color model. Our commonly used color spaces mainly include RGB, CMYK, Lab and so on. A specific color space is the standard of color application.

The difference between color space and color model;

Color space and color model are easily confused concepts. From the above explanation, you should know that color space is a subset of color model, and a color model may contain multiple color spaces.

All RGB color spaces can be represented by the above three-dimensional cube, but in different RGB color spaces such as sRGB and Apple RGB, the same position coordinates (such as 255,0,0) represent different colors and color gamut.

RGB is a color space, which describes colors through three primary colors: red, green and blue. RGB color space is the most basic, commonly used and hardware-oriented color space in image processing. The components of RGB color space are closely related to brightness, that is, as long as the brightness changes, the three components will change accordingly. Therefore, RGB color space is suitable for display system, but not for image processing.

In the color space standard jointly formulated by Microsoft and Hewlett-Packard in 1997, sRGB has a very small color gamut, which is the smallest in common color spaces, and can not even completely cover the color gamut of various CMYK color spaces.

Due to the small color gamut space of sRGB, it is not recommended for professional prepress users. Mainly used for web browsing.

In general consumer digital cameras, sRGB is often used as a color gamut standard in cameras, so that captured images can be displayed in output devices such as monitors or printers without processing. High-end or SLR digital cameras offer Adobe RGB and sRGB color gamut options.

Color space standard developed by Adobe in 1998. The purpose of the development is to create a workspace by using computer monitors and other devices, which includes as many colors as possible in the RGB color mode of CMYK color printing. Adobe RGB can have a much larger color gamut than sRGB, and can completely cover sRGB. It can almost completely cover the CMYK color space.

Kodak's color space standard is often used in high-end cameras, and it is also the default color space of Adobe Lightroom.

Because the three primary colors of ProPhoto RGB are defined as colors that cannot be recognized by human eyes (non-existent colors), its color gamut is very large, covering 90% of the color gamut of CIE Lab, and even partially exceeding the geographical scope of CIELAB, providing considerable processing space for photography and post-production.

CMYK color space, that is, printing four-color space, is a color matching mode used in color printing. Based on the principle of three primary colors (cyan, magenta and yellow), black ink is added and four colors are mixed and superimposed to form the so-called "full color printing".

The CMYK color space standard formulated by Japan Printing Industry Association is the default CMYK color space of PhotoShop in Asia-Pacific region.

In addition, the equivalent series color spaces of Japan Color 200 1 uncoated and Japan Color 2002 newspapers are suitable for different printing papers and processes.

This is the CMYK color space developed by American printing industry. The Web in the name has nothing to do with the network. The web here refers to the web. The default CMYK color space of American PhotoShop (the new version is US web Coated (SWOP) v2).

Its color gamut is similar to that of Japanese Color 200 1 coating.

Generally speaking, Lab color model refers to CIE-Lab model. Lab color model makes up for the shortcomings of RGB and CMYK color models. Lab color model consists of three elements, one is brightness (L), and A and B are two color channels. A includes colors from dark green (low brightness value) to gray (medium brightness value) to bright pink (high brightness value); B is from bright blue (low brightness value) to gray (medium brightness value) and then to yellow (high brightness value). So this kind of color will produce a bright color after mixing.

The Lab model is established according to the international standard of color determination formulated by Commission International E Eclairage (CIE) in 193 1. The color mode improved and named in 1976.

The lab mode defines the most colors. Lab mode has nothing to do with equipment, light and equipment, and its processing speed is as fast as RGB mode and much faster than CMYK mode. Therefore, we can safely and boldly use Lab mode in image editing. Moreover, the color of Lab mode will not be lost or replaced when converting to CMYK mode. Therefore, the best way to avoid color loss is to edit the image in Lab mode and then convert it into CMYK mode for printing.

Within the range of color expression (below), the first one is Lab mode, the second one is RGB mode, and the third one is CMYK mode.

HSL and HSV are both representations of points in RGB color model in cylindrical coordinate system. These two representations are more intuitive than the geometric structure of RGB based on Cartesian coordinate system.

HSB color mode is a color mode based on human eyes, which is a common color mode in popular design software, where H stands for hue S stands for saturation; B stands for brightness.

In PhotoShop, the color picker and the hue \ saturation command use the HSB model.

In reality, the color space used by various devices may be different, because each device will give priority to the color space that suits it best. When our photos need to be accessed on high-end monitors, we will use Adobe RGB color space, when photos need to be shared on the network, we will use sRGB with a smaller color gamut, when we need to print photos, we will use Japan Color 200 1 coated CMYK color space, and when we need to adjust and process photos, we will use ProPhoto RGB to minimize the color loss of images. Therefore, we should use color space reasonably according to different purposes. About the specific setting and application of color space, I will explain it in detail in the next color management tutorial. See you next time!