Wednesday, June 27, 2012

Digital Rich Blacks

Simply put, a “rich black” or “4-color black” is a black that is composed of all of the CMYK colors. And the best use of a rich black is when creating digital, full color illustrations or graphics for offset printing or digital inkjet output. In the most basic terms, CMYK or Cyan, Magenta, Yellow, and Black refer to the set of inks that are used in standard 4-color offset printing. Pictures in books and magazines that appear to the naked eye to be full color, are actually made up of varying percentages of CMYK. Interestingly, programs like Adobe Illustrator provide a black swatch that is not full color consisting of 100% Black, and 0% of Cyan Magenta and Yellow. I refer to it as a “flat black”. However, most images are made up of color choices, each being composed of more than one CMYK color. So it stands to reason that a black also made up of 4-colors will perform better in full color illustrations and graphics.


Creating a Simple Rich Black

Create a new CMYK swatch. In the CMYK mode, set the black to 100%. Set the cyan, magenta, and yellow all to the same percentage. Depending on whether you are using a lighter palette of colors or a more saturated one, I recommend setting them to at least 30% and no more than 60%. So setting all the colors to 100% is not advisable. It is important that the CMYK percentages when totaled do not exceed a number of 360, and optimally should be in a range well below that. The setting in the figure below adds up to 220. Web or sheet-fed offset presses can handle a maximum ink saturation of 360, but exceeding that level of saturation can cause some print production issues.

Example of a simple rich black.

Flat black or default black.

Creating a Compatible Rich Black

For Adobe Illustrator users, an alternative method is to create a new swatch, but this time select RGB or HSV mode and make sure all values are set to 0. Then before clicking OK, switch back to CMYK mode. You will notice that very precise percentages, broken down to 100th’s, have been provided for each of the CMYK colors. Then click OK. Although the percentages seem somewhat strange, these percentages will match the default black percentages used by Adobe Photoshop. This is a good method to use if you intend on exporting your vector work into Photoshop for further refinement.

Compatible rich black in Adobe Illustrator.
Adobe Photoshop default CMYK black.

To actually see the difference on screen with Adobe Illustrator, you can select preferences to “Appearance of Black”, see below. And surprisingly enough, with most displays, you can see a change of appearance in your illustration or graphic on screen. With the CRT monitors it wasn’t always the case.

Adobe Illustrator Preferences dialog box with black examples.

Using a Flat Black

Now it may sound like there isn’t any reason to use a flat black, but that isn’t the case. A flat black works well for artwork that uses spot colors such as Pantone colors where the colors will be reproduced as separate inks. Some examples would be for screen printing t-shirts and banners or for flexographic printing of packaging, labels and the like.