When to use CMYK and when to use RGB
If you have never ordered any printing before then there is a good chance you may not understand what the sign professional is talking about when she is referring to CMYK or RGB. Both CMYK and RGB are color models but they are very different. One is used in printing and the other involves viewing color using electronic outputs to view light like computer screens, televisions, mobile phones. When it comes to digital printing you sign you need to know the differences between CMYK and RGB so that you prepare your art file correctly to get the colors you want.
The RGB color model is made up of three colors of light that can be displayed together to make a wide range of colors. The colors of light are Red, Green, and Blue hence the RGB. When you shine the red light, the green light, and blue light in various ways the human eye will see these colors mix in a way to see a rainbow of colors. This is called an additive color model because you are adding light to change the color. RGB is used for reproducing color using electronic devices like LED televisions, computer screens, video projectors, jumbo screens at stadiums, mobile phones, etc. Creating your artwork in RGB mode is not good for digital printing your sign or business card for example, but RGB is good for creating a smart phone app or creating your logo for a website.
CMYK is a subtractive color model which is used in the printing process. CMYK stands for the four colors of inks that would be used by your commercial printer: cyan, magenta, yellow, and key (black). This four color process is started by printing on a white surface (for example white paper) and by putting down layers of the cyan, magenta, yellow, and black in various degrees you are masking the white thus reducing the amount of light reflected by the white. CMYK is the color model of choice for digital printing posters, business cards, post cards, vinyl banners, billboards, and other signs.
CMYK and RGB in Adobe Photoshop or Illustrator
So when you are creating your art file you need to determine how your art will be viewed in order to choose which kind of color model you want to use. If your logo is going to be viewed on the internet or mobile phone, then you need to use RGB. If you are going to print a business card or sign you should use CMYK. When you are in Adobe Photoshop or Illustrator you can choose the colors and get the CMYK or RGB values so you can find or pull up that color in the future. Knowing these values are also useful if you need to tell your sign shop what color to match the red in your logo to. When you are in these design programs like Photoshop or Illustrator you can find these values while in the color picker window. Below are some screen shots.
It is also important to make sure that your art file is saved in the right color mode when you hand it off to your web developer or print shop. If you have an art file ready for a sign but you don’t know what color model you are using. You can check out this video on how to check which color mode your file is in and change it if you need to.