The principle of color correction

Color scientist RWGHunt once said: People can feel more than 10 million different colors. We cannot remember all colors. If we can measure colors, we can control the colors.

In the early days, color analysis was used to analyze the quality of homework and math equations, and qualitative analysis of visual psychology was used to correct natural colors. The three elements that produce color are the specific light source, the matching object, and the standard observer. The International Commission on Illumination CIE 1931 did a color matching experiment with a 2 degree angle of view based on the principle of color mixing. The response of the eye to light was quantified. Three reaction curves were obtained for the red, green, and blue cell responses, which we called the 1931 Color Matching Function. In 1964, color matching experiments at 10 degrees were performed.

D50 is the standard illumination body of CIE, x-bar, y-bar, and z-bar are the color matching functions of the 1931 standard observer, respectively. The result of stimulating the light to the eye's quantification is to represent the tristimulus value as three data, respectively XYZ. To get X, just adding each of the wavelengths (D50 values ​​*x-bar* objects) to get X, Y and Z is the same algorithm. The tristimulus values ​​are then converted into horseshoe-shaped chromaticity coordinates x and y, while the chromaticity coordinates of the D50's standard light source are located in the horseshoe white area. That is, the spectrum of the read color patch (380 nm to 730 nm) is converted to XYZ or Lab using the formula for convenience of calculation. According to different colors, it can be verified from here that when the observer does not change, and the reflected spectrum of the illuminated object does not change, but the light source changes, so the color data is also different. For example, when you use printed materials to look at customers, you should look at the bottom of a standard light source. If you don't use a standard light source, the color may not be the same, because the light source will not see the same color.

There are some instruments and software that can be measured in a spectral manner. Finally, it is determined how much the standard light source is used. It may be 6500 color temperatures. If you can assume that you can know the color temperature of the customer, you can substitute this color temperature. The ICC profile made out there is more consistent. That is to say, what is its reflectivity at every ten nm, and a spectrum can be converted to a color by integrating out a spectrum. The CIE digitized color representation is to calculate the tristimulus value (XYZ) and the color space of CIE Lab. Calculations. So the instrument will show the measured color data, which is consistent with what the eye sees. So when doing color measurement, the instrument is also calculated according to the person's way. If you use CIE Lab, because Lab is probably more difficult to understand, that is to say in the end what the color is, and then converted a color representation Lch, Lch then refers to the chroma, CHROMA, hue angle is how much, then you can use this one The color representation shows how this color is probably located.

The true meaning of the color data is the reflectance of the object, the CIE standard light source, and the human color matching function. Finally, the product of the equations yields a data XYZ. There is a website dedicated to color correction, it can input a lot of spectrum, it can help you convert to RGB, Lab, Lch can be converted in various ways is no CMYK. For example, XYZ to convert RGB, Lab can convert RGB, color space and Lab how to use this formula, as long as the input data can be, so this pair is very easy to use in color calculations,


Source: HC Network