What is RGB and CMYK?
RGB and CMYK are two different color modes that are used in digital and print design respectively. RGB stands for Red, Green and Blue and is an additive color model where mixing different amounts of the three primary colors produces other colors. CMYK stands for Cyan, Magenta, Yellow and blacK and is a subtractive color model used in print design where combining the four inks absorbs certain wavelengths of light to produce different colors. Understanding the difference between the two and when to use each one is important for designers working across digital and print media.
How RGB Works
RGB is called an additive color model because it starts with black (an absence of light) and adds varying intensities of red, green and blue light to create the colors we see on digital screens.
| Color | Red | Green | Blue |
|---|---|---|---|
| Black | 0 | 0 | 0 |
| White | 255 | 255 | 255 |
| Red | 255 | 0 | 0 |
| Lime | 0 | 255 | 0 |
| Blue | 0 | 0 | 255 |
In the RGB color model, each color is assigned an intensity value from 0 to 255 for each of the red, green and blue components. Black is an absence of all three colors with RGB values of 0,0,0. White has full intensity of all three with RGB 255,255,255. Primary colors are red (255,0,0), green (0,255,0) and blue (0,0,255). Combining these primary colors in different proportions allows us to create millions of other colors.
For example, yellow can be created by mixing full green and full red with RGB values 255,255,0. Cyan comes from green and blue, 0,255,255. Magenta is made with full red and blue at 255,0,255. By varying the intensities, millions of shades in between these primary and secondary colors can be created.
This method of starting with black and adding light to create color is ideal for representing colors in a digital format. Pixels on screens like TVs, phones and computers use the RGB model to reproduce colors by emitting tiny red, green and blue lights in sub-pixels. Varying the brightness of these sub-pixels allows the pixels to produce millions of colors.
How CMYK Works
While RGB adds light to create color, CMYK works by absorbing certain wavelengths of light through combinations of colored inks. It is a subtractive color model, starting with white and progressively removing colors by overlaying translucent inks.
| Color | Cyan | Magenta | Yellow | Black |
|---|---|---|---|---|
| White | 0% | 0% | 0% | 0% |
| Black | 0% | 0% | 0% | 100% |
| Cyan | 100% | 0% | 0% | 0% |
| Magenta | 0% | 100% | 0% | 0% |
| Yellow | 0% | 0% | 100% | 0% |
The CMYK color model uses four ink colors – Cyan, Magenta, Yellow and blacK. The percentages refer to the concentration of each ink. White paper is the starting point. Applying 100% of black ink absorbs all light and gives black.
The primary subtractive colors are cyan, magenta and yellow. These are transparent inks that filter out their complementary color in white light – cyan removes red, magenta removes green, and yellow removes blue. Combining any two subtracts two colors, leaving the third. For example, cyan and magenta make blue by filtering out red and green.
But combining all three primaries doesn’t make true black due to impurities in real-world inks. So black ink is added as a fourth component, ensuring true blacks and also allowing finer control of dark tones.
The CMYK model allows printers to accurately reproduce color images by layering these four standard inks on paper. The colors can be reproduced reliably despite variations in ink properties between different manufacturers.
Key Differences Between RGB and CMYK
While both RGB and CMYK can reproduce a wide range of colors, there are some key differences between the two models:
| RGB | CMYK |
|---|---|
| Additive mixing of light | Subtractive mixing of inks |
| Emissions from red, green and blue light | Absorption by cyan, magenta, yellow and black inks |
| Used for digital screens | Used for print design |
| RGB gamut – wider range of colors | CMYK gamut – narrower range of reproducible colors |
| Integer RGB values from 0 to 255 | CMYK values from 0% to 100% |
The key point is that RGB has a wider gamut and can produce more vivid colors suited for digital screens. CMYK has a smaller range with duller tones but more accurate for printing. Some colors like bright neon tones can be created in RGB but not accurately printed in CMYK.
When designing for both digital and print, it’s important to keep these gamut differences in mind. Ideally CMYK colors should be specified from the start for print design work. For digital, RGB is preferred. Converting between the two can lead to unexpected color shifts.
Converting Between RGB and CMYK
While each model has its own gamut, software like Photoshop or Illustrator allows converting between RGB and CMYK with different rendering intents:
– Perceptual – Favors visual relationships over accuracy, shifting out-of-gamut colors while preserving color ratios
– Relative Colorimetric – Leaves in-gamut colors unchanged, only converts out-of-gamut colors
– Saturation – Tries to maintain vividness, suited for charts and graphics
– Absolute Colorimetric – Leaves both in-gamut and out-of-gamut colors unchanged, no conversion
But these conversions are only approximations. Some colors will inevitably change due to the different gamuts. For best print results, directly specifying CMYK values is recommended whenever possible during the design stage.
RGB to CMYK conversion often desaturates vivid colors, so some additional tweaking is needed to maintain saturation. Black levels also need to be adjusted in CMYK to hit the right visual balance.
The opposite CMYK to RGB conversion can be more tricky. The smaller CMYK gamut means some colors don’t have exact RGB equivalents. Converting these colors simply stretches them to fit the RGB gamut. This can result in over-saturated neons that look very different from the original CMYK color.
So check conversions carefully and make adjustments to get as close as possible to the original intent. Understanding these gamut differences allows designers to plan and compensate where needed.
Uses of RGB vs CMYK
Given these fundamental differences between RGB and CMYK, they are suited for the following uses:
RGB is used for:
– Digital screens – TVs, phones, tablets, monitors
– Web graphics – JPG, PNG, GIF, SVG images online
– Apps, software and game graphics
– Video and film production
– Digital photos and digital art
CMYK is best for:
– Printed materials – brochures, posters, books, packaging
– Newspaper and magazine printing
– Promotional flyers and direct mailers
– Large format banners, signs and billboards
– T-shirt and apparel printing
– Paper stationery – business cards, letterheads
– Analog photo printing
For any design projects involving both print and digital use, it’s recommended to:
– Develop concepts in RGB for flexibility
– Finalize print versions in CMYK natively if possible
– Manage color conversions carefully between modes
– Proof CMYK colors on actual printing presses
– Adjust designs to compensate for conversion shifts
With the right color management workflow, high quality results can be achieved across print and digital media channels.
Color Management Best Practices
To help deal with shifting colors between RGB and CMYK, here are some suggested color management best practices:
– Use SWOP or GRACOL standards for CMYK printing rather than custom CMYK mixes
– Incorporate Pantone colors into designs for consistent cross-platform color
– Always do test prints and check final separations before approving jobs
– Askprinters for color proofs to view CMYK results firsthand
– Use ICC profiles to manage conversions between color spaces
– Work in a linear color space like Adobe RGB for best conversions
– Maintain digital and print versions of artwork rather than converting back and forth
– Check designs on actual devices – mobile, web, print, etc.
– Adjust critical colors manually after conversions to match appearances
Proper color management ensures colors are consistent and accurate across all media from initial concept to final print or digital product. Matching RGB on screen colors to real world CMYK prints is achievable with care and testing. Understanding the principles underlying RGB and CMYK is the first step to effectively utilizing both in design projects.
Conclusion
RGB and CMYK provide two very different methods for reproducing color, suited for their respective digital and print applications. RGB mixes light while CMYK mixes inks, leading to different gamuts and uses. Managing and converting colors between the two requires an understanding of their limitations to obtain optimal results across platforms. With the right color workflows, both color modes can be used effectively together in a unified design strategy spanning digital and print.
