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RGB vs CMYK: Guide to Color Spaces

RGB vs CMYK: Guide to Color Spaces
Filip Pejanovic

By Filip Pejanovic

5 min read

Imagine a color, any color. It could be bright and vibrant, or dark and dull. You’ve probably seen it somewhere, maybe in your favorite movie or on a cool poster hanging in your office. Combine enough colors and soon you’ve got a cool design. If you’ve ever wanted to put that design on something and sell it, you’ve probably done some tinkering in Photoshop.

The print file you get out of Photoshop and the image as it appears on your t-shirt might not be the same though. Often, the difference has to do with color spaces, and why there’s a difference between how colors appear on our screens and how they look in real life.

In this post, I’ll go in-depth about one of the trickier color-related topics–RGB vs. CMYK color spaces. I’ll break it down by answering some of the most important questions:

  • What are RGB and CMYK and when do we use them?
  • What is the difference between RGB and CMYK?
  • What is the most suitable color space for printing?
  • Is CMYK better than RGB?

Let’s start with some basic color facts. All the colors we can see with our eyes are part of the visible color spectrum. They’re represented in the circle below.

visible-color
Visible color spectrum

Because of technological limitations, our computer screens and other similar devices can’t display every color that our eyes can see. Instead, display screens show colors in the RGB space.

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What is RGB?

RGB stands for the three colors Red, Green, and Blue.  The color space uses Red, Green, and Blue light to make new colors. You can see the RGB range compared to visible colors in the picture below.

rgb-color
RGB color spectrum

Each pixel in the digital devices we use has three tiny, slightly overlapping RGB light sources that trick our eyes into seeing just one color when looking from a distance.

So if you wanted to show something yellow, the RGB pixel would shine green and red light together, while leaving the blue one off. The stronger the light intensity, the brighter the colors appear. At full intensity, the combined colors appear white and at zero intensity they appear black.

What’s great about the RGB color space is that it gives you a wide of range color combinations you can play with when creating digital designs.

When is the RGB color space used?

RGB colors are used for digital purposes. Any images that appear on a digital screen will be displayed in RGB. This is important to remember when creating your print files since you’ll most likely do it in Photoshop or similar software.

If you’re Printful customer, we recommend you create your print files in CMYK and then convert them to RGB color space, or, to be exact, sRGB color profile. I’ll explain the exact reasons later, but first, you might be wondering what CMYK is.

What is CMYK?

CMYK stands for Cyan, Magenta, Yellow, and Key (which is just another word for black). It’s basically the opposite of RGB; it uses colored ink to mask colors on a light background. This light background (usually white) reflects light, so each layer of ink applied subtracts from white light to make new colors.

For example, if you combine Yellow and Magenta (meaning subtract yellow from magenta), then you get Red. You can combine any two Cyan, Magenta, or Yellow colors to create one of the three RGB colors.

If it’s confusing, just try to think about drawing with colored pencils. If you combine two different colors, you’ll get a third. It’s the same idea behind CMYK.

When you combine all three colors, you get grey. Since we also need black, it’s the fourth color. This is also why CMYK is sometimes called the four color space.

Compared to RGB and visible color, the CMYK range looks like this:

cmyk-color
CMYK color spectrum

When is the CMYK color space used

CMYK is recommended for any printed material. This includes all of Printful’s products, from apparel to mugs, posters, and more.

Why do we use CMYK for printing? It reflects the colors more accurately.

What is the difference between RGB and CMYK?

Key Differences RGB CMYK
What does it stand for Red, Green, Blue Cyan, Magenta, Yellow, Black
What's it used for Digital Printed
Variety of colors Lots of colors, vibrant Fewer colors, sharper
Photoshop settings Default Must convert from RGB to CMYK
Accepted print file YES NO

I like to think of RGB as a lit match in a dark room, while CMYK is a picture of the lit match in the dark room.

With CMYK, color intensity is not as flexible as in RGB. It’s just impossible to replicate on ink paper or fabric the same intensity and brightness that a digital display can show.

This means some RGB colors will show up differently when printed in CMYK. The software you’re designing in (Photoshop and others) is set to RGB color space by default (in most casses: sRGB color profile specifically). That’s fine if your designs are only going to appear online, but printed designs need to be done in CMYK. You can read Printful’s Color Matching Disclaimer for more details about this.

We recommend using CMYK when designing print files for a few reasons:

  1. RGB files tend to be smaller
  2. Only advanced software has the option to design in CMYK

How to convert RGB to CMYK

This depends on the software you use and which version you have, so I recommend finding a tutorial online for the software you have. Here is a short RGB to CMYK Photoshop CC tutorial.

Is CMYK better than RGB?

CMYK and RGB have different uses, and it’s important to know when to use which. Since we’re focusing on printing, we want to stay within the CMYK range. However, technology is advancing and Printful’s printers can already print colors outside of the usual range, although we still suggest sticking to approved methods. What happens if you don’t convert your RGB colors to CMYK?

Let’s take a look at this design as it appears in Photoshop:

cmyk-printed-example
Digital design example

As you can see, the colors stand out and the shadows are visible. Now let’s compare it to a printed t-shirt with the same design:

https://files.cdn.printful.com/o/upload/bfl-image/75/934_l_comparing-colored-corrected-shirts.png
Not color corrected vs color corrected

Clearly, it doesn’t look the same. The t-shirt on the left looks flat and dull and hasn’t been color corrected. The t-shirt on the right matches the vibrant colors of the original design, it was color corrected.

You can see how much of an improvement this is. The colors stand out, they’re brighter than they were before and the printed version really captures what the original design was going for.

Combine your colors

Be brave and experiment with your color designs. Figuring out the right ones might take some work, but you’ll get there soon enough. Just remember these differences between RGB and CMYK and you’ll be a color expert in no time!

And don’t worry if you’re nervous about setting up your design files correctly, we’re more than happy to help you with that as well.

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By Filip Pejanovic on Feb 12, 2019

Filip Pejanovic

You can find me devouring the dusty marigold pages of my First Edition Wheel of Time collection while enjoying a plate of fluffy pancakes next to my adopted goldfish, Harold.

You can find me devouring the dusty marigold pages of my First Edition Wheel of Time collection while enjoying a plate of fluffy pancakes next to my adopted goldfish, Harold.

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Filip Pejanovic

By Filip Pejanovic

5 min read Feb 12, 2019

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