Converting RGB to CMYK, Plus Other Things to Know About Color Models

There are two main ways to create an image — with physical pigment or with light. Many graphic designers use both as they operate in the realm of digital and print media. Comparing RGB to CMYK reveals several key differences between the color models, including when to use them and how to switch from one to the other. Here’s what graphic designers should know about these two methods for bringing a design to life. 

What Are RGB and CMYK?

RGB and CMYK are two distinct ways of mixing color in graphic design. Although they both produce images, they use different techniques to do so. 

RGB: The Light-Based Method

Designers use RGB for anything they want to display on a monitor or screen, such as videos, web designs, or digital logos. RGB stands for “red, green, blue.” It refers to the fact that every image is broken down into pixels, and each pixel, in turn, is broken down into three colors — red, green, and blue. 

Turning on the red and green subpixels all the way — visually combining them — results in a yellow pixel. A dim red subpixel and bright blue subpixel would make a purple pixel. Adding all three subpixels together creates white, just as it does when aiming red, green, and blue spotlights at the same point on a wall. RGB is an additive color model, meaning one in which adding all the colors together makes white. 

CMYK: The Pigment-Based Method

Designers use CMYK for printing out a design on a physical medium, such as paper or cloth. CMYK stands for “cyan, magenta, yellow, key.” “Key” refers to a printer’s key plate, the plate that holds the most detail in an image. The key plate is black. As a helpful shorthand, graphic designers can remember that K is black because the word “black” ends with that letter. 

Printers use physical pigment, not light, to create an image. Ink behaves very differently than light when it comes to color. 

Printing yellow and magenta ink blotches on top of each other creates red. Yellow and cyan make green, while cyan and magenta make blue. Adding all four colors together in the CMYK system creates black. This is called a subtractive color model because subtracting colors from the page — even though that isn’t possible with ink — would make the page whiter.

CMYK printers layer colored dots on top of and next to each other in precise amounts to reproduce an image. Unlike pixels, the size of the dots is not consistent. It depends on the absorption of the paper, ambient humidity, ink density, printer pressure, and other factors. CMYK printing is generally less consistent than an RGB design. 

The History of RGB and CMYK

Jacob Christoph Le Blon, a 17th-century painter and engraver, invented the method that laid the foundation for CMYK and RGB color systems. He used the mezzotint technique to engrave either three or four metal plates with ink to produce prints in a wide variety of colors. 

With the invention of color photography, computers, and half-tone printing hundreds of years later, it became possible to break images objectively into their color components. Thus, RGB and CMYK were born. They are still the primary methods of displaying images in print and onscreen.

Problems With Converting RGB to CMYK, and Vice Versa

Graphic designers who want to print a design will need the image to be in CMYK, because that’s what printers use. Ideally, they should create the image using CMYK in the first place. 

Converting RGB to CMYK will always change the colors in the image. Although the difference may be subtle, it can also make the final design look completely different, such as by making a light blue sky appear dark or changing a person’s eye color. 

Similarly, scanning and uploading a CMYK image to the computer can also create color shifts. However, sometimes designers might create a digital design in RGB mode and then later decide to print it. In that case, there are several ways to convert RGB to CMYK. 

How to Convert RGB to CMYK

Photoshop makes it easy to switch between color modes. Graphic designers can simply open an image in Photoshop and click on the Image tab. From there, clicking on Mode and then CMYK will convert an RGB image to CMYK for printing. 

Photoshop creates RGB images by default. To create a new CMYK document in Photoshop, users can navigate to File and then New. Under the New Document window, there is an option to change the color mode to CMYK, making it much easier to design an image for printing right from the start.

To convert RGB to CMYK in Adobe Illustrator, users can navigate to File, Document Color Mode, and CMYK Color. 

Why Does CMYK Look Washed Out?

The RGB color model produces brighter, more vibrant colors than CMYK because the colors are intended for use on a screen. 

The effect is especially pronounced when comparing an RGB image onscreen to a printed CMYK version of the same image. Because screens are backlit, they can make an image look even more vivid than it would be on paper or cloth. Additionally, images can look more faded as a printer starts running out of specific ink colors. 

What Is Pantone?

One option for graphic designers who want brighter prints is to use Pantone colors. Also called spot colors, these specially formulated inks have unique colors and are much brighter than CMYK. They can even be metallic or fluorescent. 

Pantone’s color-matching technology, which contains 1,867 solid colors, allows designers to print the exact shade of purple or chartreuse they want. It’s good for more than just designing t-shirts — it allows brands to be consistent no matter where they advertise, whether on a billboard or the side of a stadium. 

Pantone doesn’t layer colors on top of each other like CMYK does. Instead, Pantone inks are mixed to create the desired color, much like mixing paints at the hardware store. They are then put onto one plate for printing on a special machine that must be prepped for each job. 

Why Does Black Look Gray in CMYK?

To get a true black in CMYK, designers must use a mix of cyan, magenta, yellow, and K. Remember, CMYK is a subtractive color model, so designers have to mix all four base colors to get the blackest shade. Using only K will result in a deep gray color. 

The darkest black shade in CMYK is C-75 M-68 Y-67 K-90. Dragging the color picker all the way to the bottom left will select this shade of black. Alternatively, designers can manually enter these values to ensure they’re choosing the right hue. 

Bringing Designs to Life

Graphic designers should familiarize themselves with the RGB and CMYK color models. Digital media like computers and TVs use RGB, a light-based system that employs red, green, and blue subpixels to create different-colored pixels. The CMYK color system — specifically for printers — layers cyan, magenta, yellow, and black inks on top of each other to print an image on paper, cloth, or another physical medium.

Both systems have merit to a graphic designer. Whether onscreen or on paper, RGB and CMYK bring an artist’s ideas to life.