Print basics: How to use RGB and CMYK correctly

Using color profiles for better design results

Oktober 25th, 2011, 10:24 am

The second part of our basics is all about colors. We receive a lot of print data with the wrong color mode for perfect offset print results. This article explains RGB and CMYK, differences between the two and when you should use which one.

What is RGB?

All colors of the RGB color model are created with the 3 primary colors Red, Green and Blue. Mixing these light primaries equals white. This additive color method can display a very wide range of colors.

The image below is a close-up shot of a monitor showing the three color grid of a typical monitor.

Where is RGB used?

Every monitor displays colors in RGB mode – depending on the monitor some do better and others worse ;) So, basically when you create something for screen display, such as a website or a funky button in an app, you create your file in RGB mode.

by Jordan McLane, flickr.com

Why RGB is not color-fast on a screen

Multiple factors influence the quality of color depiction on a monitor, e.g. color depth (also depending on the graphics chip), age, quality, color temperature, display type and last but not least lighting conditions in rooms and the angle of view. Some of this can be minimized by monitor calibration. Most professional designers do this on a regular basis.

Compared to the CMYK color palette, the RGB color model is very wide but it also has some drawbacks. The yellow color spectrum doesn’t provide as much different colors as other color palettes. Blue and purple color ranges in turn are much more varied in RGB. Metallic colors like silver or gold as well as differences between matte and glossy can’t be displayed with RGB, which makes it not the best choice for printing.

What is CMYK?

The primary colors of the CMYK color model are Cyan, Magenta, Yellow and black (black, Key). CMYK colors are added on top of each other. The more color (cyan, magenta, yellow) you add the less light is reflected. As you basically take away brightness you call this a subtractive color model. Black is used to achieve more contrast since this kind of color mode is kind of „flat“.

Where to use CMYK?

It’s mostly used for printing.

Why do colors change when exporting RGB to CMYK?

As I mentioned before: TheCMYK color range is a lot smaller than RGB. When you convert a larger color model to a smaller one some colors, especially the bright and shiny ones, go „missing“. The other way around (scanning printed images) causes less issues as the target color model is bigger and most color ranges can be accommodated.

Due to this effect most designers set up the color model right at the beginning. If you know it’s going to be flyer for print you better start with CMYK right away. Here’s how:

Preparation of print data

Preparing print data is quite easy. Just make sure to use CMYK mode* when starting a new project in Photoshop and InDesign.

*The recommended color profile for sheet offset is ISO Coated v2, available from the ECI website. Download eci_offset_2009.zip and install the profile by double clicking the correct file in the zip folder.

Photoshop

InDesign

Adjustments in Photoshop

Export in InDesign

Pictures which you’re importing for your project are almost always in RGB and have to be exported to CMYK when creating a PDF.

We hope you liked the article and we could provide some useful information. If you have questions don’t hesitate to ask. :)

MO

One Response to “Print basics: How to use RGB and CMYK correctly”

  1. Saso Gjorevski says April 25th, 2012 um 2:28 pm

    Good info about RGB and CMYK and their use in technology of printing.

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