RGB vs. CMYK: Understanding Color in the Digital World

DSLR Camera
Brian Ach / Stringer / Getty Images

RGB, CMYK... it sounds like a bunch of alphabet soup. They are, in fact, used to describe color in the digital photography world. It is important for photographers to have an understanding of these two terms because they have a great impact on the color of your photographs, both on screen and in print.

A quick explanation is: RGB is for the web and CMYK is for prints. It is a little more complicated than that, so let's take a close look at color spectrums.

What Is RGB?

RGB stands for Red, Green, and Blue and refers to the three primary colors that can always be mixed together in different variants to produce different colors. 

When you take a photograph on your DSLR, your camera will compose your shot using an RGB spectrum. Computer monitors also work in RGB, so it is easy for users to expect that what they see on their LCD screen will be what they see on their monitor.

RGB is known as an additive color spectrum, as it relies on adding different amounts of the three colors to make different colors.

  • In the RGB spectrum, there are 256 levels of brightness which produce 16,777,216 (256x256x256) color possibilities.
  • By setting each RGB color to a setting of "0," we can generate black.
  • Likewise, a setting of "255" on each color generates white.

Therefore, RGB is the industry default for DSLRs and computer monitors, as it allows us to view colors true-to-life on screen.

What Is CMYK?

However, if we want to print our images using a correct color spectrum, we need to convert to CMYK. This stands for Cyan, Magenta, Yellow, and Black.

CMYK is a subtractive color spectrum, like cyan, magenta, and yellow pigments are used as filters. This means that they subtract various amounts of red, green, and blue from white light to produce different colors.

Therefore, an image displayed on a computer monitor may not match a print, unless the RGB spectrum is converted to CMYK. Although many printers now convert from RGB to CMYK automatically, the process is not yet perfect. As RGB doesn't have a dedicated black channel, blacks can often appear too rich. 

Working With Printers

Technology has evolved quickly in recent years and it is not always necessary to do a conversion from RGB to CMYK when you need to print a photograph. However, there are some instances where this is necessary.

Printing at Home

Most desktop printers in homes and offices use CMYK inks. The printing technology in both the software applications and the printers now does a very nice job of automatically converting RGB colors into CMYK.

For the most part, the home printer does not need to worry about conversion. However, if you find that your blacks are not quite right, you may want to do a conversion and a test print to see if that helps.

Working with Commercial Printers

There are two types of commercial printers that you may work with and some may ask you to convert a photograph to CMYK.

In most instances today, you will not have to make a conversion. This is particularly true when using a photo printing lab. Their software and technicians will usually handle most color challenges to produce the best photographic prints possible. They want to make the customer happy and know that everyone does not have a full understanding of technology.

If you take your work to a dedicated graphics printer for things like postcards, brochures, etc., they may ask for the image in CMYK. This is because it is the format that they have always worked with. CMYK, also known as four-color printing, dates back to the days of color printing and processing before digital technology was even imagined.

Converting From RGB to CMYK

If you do need to convert an image from CMYK to RGB for a printer, it is very simple and almost every image editing software has this option.

In Photoshop, it is as easy as navigating to Image > Mode > CMYK Color.

Once you send the file to your printer, work with them and do a test print (a proof) to make sure that the color is what you expect. Again, they want the customer to be happy and will be glad to walk you through the process.