Color correction has always been a headache for computer graphics, because some colors on the monitor cannot be printed by UV, or there are serious color differences. If it cannot be corrected at the design stage, it will be too late when the finished product is printed.
Color cast problem of RGB to CMYK
UV printing uses magenta, cyan, yellow, and black, so the colors are specified by CMYK. As long as CMYK is determined, it means that the proportion of UV ink for printing is determined, and the color will usually not be a big problem (from the general point of view). However, the color in the computer is represented by RGB mode, so to print RGB colors, it is necessary to go through a color conversion step, which will cause two problems:
The first problem is that UV ink cannot print all RGB colors. Usually, high-brightness colors, fluorescent colors, and metallic luster cannot be printed, so they have to be replaced by CMYK. If you find that the selected color box has an extra triangular exclamation mark when using Photoshop, or an exclamation mark is added after the CMYK value, it means that the color cannot be printed.
The second question is, what conversion standard is used when converting RGB to CMYK? Even if a certain RGB color can be converted to CMYK, it does not mean that the actual color of the UV ink will be the same as the color displayed on the screen. Usually, the biggest problem occurs in cyan.
Solution 1. Use CMYK to specify the color
Some software, such as CorelDRAW and Photoshop, will take special considerations for the accuracy of the conversion between RGB and CMYK. As long as you use CMYK directly to specify the color in the software, you can get a result that is quite close to the actual printing, so try to use CMYK mode to operate. Photoshop can convert the image file to CMYK mode for editing (MENU: Image > Mode > CMYK color), which can completely avoid using colors that cannot be printed. The disadvantage is that most filters cannot operate in CMYK mode. There is really no way to temporarily convert to RGB mode and then convert back to CMYK mode after using the filter.
Solution 2. Use the printing color table to query the color
Another way is to use the printing color table to query the actual printed color. The color table is a reference template for color values, which lists various combinations of CMYK for the query. Therefore, when you want to choose a specific color, first find the color you want from the color chart, and then enter the CMYK value marked on the chart into the software. For most people, this is the most reliable way to calibrate the color.
The price of the color chart ranges from US$50 to US$150, and most bookstores cannot buy it. You have to go to art clubs or bookstores that specialize in selling art books to find it.