Tuesday, January 8, 2013

Digital Printing Profiles Part 1: Theory

What Is A Profile?

A digital profile is a descriptive index that is used to define of properties and limitations of a color space. A profile registry is a set of finite values that create meaning for digital display media or physical output media. Profiles exist for hardware devices, within software programs, and for physically displayed media.

What Is a Color Space?

A color space is finite set of colors that is resident within a specific color environment. Each digital environment or physical environment has its own unique color space that varies according to the data provided by a profile. A color space can be hardware, software or object based.

What Are Environments?

An environment is a device or object where a color space can be observed. Some examples of display environments include computer monitors, televisions, and IOS mobile devices such as cell phones and tablets, and digital cameras. Software programs that illustrators use like Adobe Photoshop and Illustrator are also environments that contain color spaces. And finally, an often overlooked, and chiefly important environment, is the material output devices print on, such as inkjet papers and commercial printing papers. Etc.

Hardware device profiles are typically referred to as being “embedded”; while “workspace” profiles refer to a software environment; and “destination” profiles refer to an images final display.

The Color Space Dilemma

Each environment has its own unique color space. No two types of devices, software programs, or materials are alike. For instance, any of us who have experienced placing an illustration in InDesign that was created in Photoshop, have noticed a shift in the appearance of colors. Even though the two programs are both Adobe products, each one has its own, different, “color space”, or “color mode”. And, there can be several color spaces within one software program. For further information on color spaces, see theinformedillustrator.com, September 18, 2012 post Digital Color Spaces”.

The Solution To The Dilemma

So, how can we illustrators and visual artists, know that the colors we are using in the work we are creating will be seen the way we intend them to when they are displayed in their final form? The answer is… the “profile”.

A profile acts as a translator, adjusting colors that exist in one color space for display in another. Essentially, a profile allows display spaces to talk to one and other. With a profile, an illustration or image that was created in one color space can be converted for optimal appearance in a different color environment.

Each color environment has its own unique profile. In other words, each environment has its own range of colors. For instance, the profile for an Apple iMac display is different than the profile of a Hewlett-Packard display, and the profile for an Epson 3000 printer has a different color range than that of an Epson 1900 printer. Also, each type of paper stock has its own unique profile to be used by a printer to output images. These print profiles are available directly from the paper manufacturers.

The Dilemma Created By The Solution

With each display device, software color space, output device, and final output environment in a workflow chain having a different profile; it is not unusual to end up with a profile mismatch. A profile mismatch is when the “embedded profile” does not match the working space or the destination space. A common example is when a RGB image is intended to be output as a CMYK image. By changing the RGB profile to a CMYK profile, the end result will be displayed more accurately for some destination spaces such as offset printing. It should be noted that many inkjet and dye-based digital printers prefer an RGB color space, even though they use a CMYK or CMYKRGB combination of inks to make a print. In these cases, the printer profile data has already been configured to compensate for a color environment shift.

The out of gamut color warning.

The Solution Solved

A thorough “color management system” is the solution for inconsistent color. The best results can be achieved by using a color managed workflow throughout the color display chain. Checking to make sure the proper color environments are being used from the display, to the software, to the printer, to the final output destination, can make a substantial difference when it comes to the quality of published images. 

How Do Profiles Work?

Profiles address the limitations of a color space. As the color workflow progresses through the display chain, the color space becomes more and more constricted. So, for instance, the expansive number of colors that are available for use in the RGB color mode in Photoshop has to be whittled down to fit in the output color space for web display, or printing in a CMYK color mode. In the process, a number of colors will fall out of gamut. In other words, they will be beyond the boundaries of the print color space. This also occurs in images created for other forms of display.

A comparison of the CMYK, RGB, and Visible color spaces. Grayed colors outside 
of their indexed spaces indicate they are out of gamut. © 2013 Don Arday.

An output or printer profile deals with out of gamut colors in two ways: 1) It ignores the colors. In other words, the colors are not recognized. To the printer, they don’t exist. 2) It shifts their value to make them become an in-gamut color. The profile makes a best guess alteration to the color to move it into gamut, and in many cases it assigns the color value of another similar color that already exists, collapsing two colors, or even more, into one.

Profiles Profiled

There are as many different profiles as there are; software programs; color spaces; output devices; and display spaces, regardless if they are digital or hard copy. So, the best visual results, and intended color consistency, is achieved by using profiles that were created for their respective destination environments. If not resident in the computer hardware or software being used, these specific profiles can be downloaded from the manufacturers websites. And in cases where profiles are not available, there are companies that can create customized profiles for nearly any situation.