Definition of color correction

Because color correction is supported by RGB optical theory, people who can correct colors will definitely "color". In reality, the color corrector can make a digital photo reach a certain psychological preference tone in a short time, while the "coloring" person skillfully touches a certain tone under unreasonable temptation. Accurately speaking, color correction is a rigorous work, with strict standards and norms, while in reality, color matching is more personal preference, without strict standards and norms.

Color calibration is color calibration. It ensures that the color of the image can be accurately reproduced by human eyes at the shooting site. A complete color calibration is usually divided into three prerequisites: equipment calibration, such as input devices and scanners; Calibrate output devices, such as printers or monitors. After accurately calibrating the input and output devices, the scanner can accurately capture colors, and the screen or printer can faithfully display colors. Color setting of image processing software, such as wide color gamut AdobeRGB 1998 color space or web page color space sRGB IFE6 1966-2. 1. Any color setting must be unified with the above 1 device to ensure that the color corrected image can reproduce the authenticity of the scene color. The color settings of digital cameras must be consistent with the above color settings, and the white balance settings must be accurate, such as the white balance of sunlight when shooting or the white balance when shooting on cloudy days. There are three main bases to distinguish and judge the color deviation of images: the intuition of colorless, weak or color-blind healthy human eyes, that is, memory color. Memory color is the constancy of the human eye to the scene, which is exactly the color of the scene irradiated or mapped by the human eye at the spectral wavelength in the visible range. If the tone of a photo or image obviously deviates from the memory color of human eyes, it can be considered as color cast. This method is mainly based on the white balance of sunlight standard light. For photos with poor color rendering of light source, it is difficult to visually observe whether there is color cast, such as artificial tricolor fluorescent lamp, ordinary fluorescent lamp, or cloudy photos. Photos with color saturation of +50% can be visually observed in the "Hue/Saturation" instruction of Photoshop image software. Generally, color cast defects can be clearly seen in photos with color saturation of 50%. Gray balance recognition method, which has a wide range of judgment, is mainly based on the constancy of human memory in photos (see 1). Identification method: Open the color picker of Photoshop software, click the object (object) that should be gray in the photo with the dropper of the sampling tool, and check the sampled color and neutral gray balance parameters on the color picker. Because the sampling point of the detection parameter is different from the pixel size of the selected sampling target, it is impossible to be completely in the absolute balance of1:1as long as the sampling color parameter is close to gray. Because the photo is not an electronic standard color card and is not filled with solid color, it is allowed to have a "color shift" formed by the reflection of ambient light. As the name implies, color correction is to correct the color deviation of photos and images. To sum up, color correction is not the "color matching" of personal preference. Therefore, color correction is a complementary color correction process of three primary colors RGB and three primary colors CMY. No matter what kind of color cast mentioned above, it must be based on the principle of neutral gray balance, take care of the overall situation of color reproduction of photographic photos, conform to the feelings of human eyes on the spot, and follow the scientific laws of photographic imaging and color quality. Generally speaking, color correction is based on three principles: the color deviation of standard color temperature (sunlight) photos is based on gray balance, which can be dark tone, medium tone and highlight. Due to the slow response of human eyes to dark parts and highlights, in color correction, the halftone gray level is basically close to 1: 1: 1, indicating that the correction is in place. For example, the sampling parameter color scale is 65438. Absolute balance mainly refers to the color deviation treatment of standard electronic signboard color cards used in teaching demonstration, such as deliberately creating color deviation in teaching, and then explaining the principle of color correction, such as calling the color swatch tool of Phtotshop to correct the sampled data obtained in the process of color correction in time. Specifically, after clicking the neutral gray block with the straw tool on the signboard color card, the balance parameters can be seen on the color board, and the color numbers of the corresponding primary colors and complementary color filters can be adjusted through the instruction of the color correction tool "Color Balance". No matter whether the shooting file format is RAW or JPG, the color correction of multi-light source photos can balance the global color of photos by adjusting the color temperature in the RAW decoding plug-in of Photoshop software, so that it is close to the color perceived by human eyes at the shooting site. You can also use the color correction tool of Photoshop software for color correction. These color correction tools include color balance, hue/saturation, curves, optional colors and even channel mixers. Are authentic optical concept color correction tools.

Strictly speaking, color correction should be a complementary process of adding or subtracting optical law data, instead of using multi-layer mask protection and rope to skillfully handle locally selected PS. Color correction is an optical physical process in which RGB and CMY complement each other to correct color. Its typical optical process is exactly the same as the color filtering principle of film processing equipment and laser processing equipment, except that Photoushop turns this hardware color correction process into an electronic filter of software to simulate a glass filter.

Because the color correction technology follows the optical laws of three primary colors and three complementary colors, the color correction of optical concept is called the "three axes" of color correction, and the effect can be obtained quickly without the technical assistance of other complex objects (ropes, layers and masks). In the process of film color correction of photosensitive materials, color filters are completely used, and electronic analog filters are used in computer image software. The process of software color correction only needs to pull the three-color slider of color correction instruction.