Tuesday, January 15, 2013

Digital Printing Profiles Part 2: Practice

Profiles are resources that are available to improve the color appearance of images. Hardware and software manufacturers provide a variety of profile options to give users flexibility in controlling image color. Embedded, workspace, and destination profiles are all available and accessible.

Color Management

Programs like Adobe Photoshop, Illustrator, and InDesign provide a “color management system” that allows many options for dealing with color non-generically. Under Color Settings the user has access to Color Management Policies, Workplace Settings, and Conversion Options to improve the quality of the flow of color from internal sources that are resident in the software used to create images, to external resources that produce the final image display.

Photoshop color settings dialog box.

Working Spaces 1.

The working space designates the working color profile to be used for a particular color model.  There are a number of options are available for each RGB, CMYK, Gray, and Spot color modes. See theinformedillustrator.com post Digital Color Spaces for more information on color modes.

Color Management Policies 2.

Color management policies oversee the operation of a particular color model. They handle how color profiles are applied, the moving of color from one document to another, and they determine if there is a profile mismatch. Essentially, how the color will behave in an image. Preserve Embedded Profiles is the default provided and in most cases is the proper selection. Preserving profiles means that RGB colors will be displayed based on perceptual appearance, or how they look best in an RGB environment. CMYK colors are displayed according to the numerical values that will be needed when an image is translated for output.

Conversion Options 3.

A Conversion Engine is used to select which software to use when handling the color conversion. Adobe (ACE) is the default setting, allowing adobe program settings to be used for conversion; but the primary function involves the “rendering intent” for the colors to be converted. The Color Conversion Engine uses Intent for the handling of “out of gamut colors” when rendering colors. There are four rendering options.

Conversion engine options in color settings.
Perceptual Intent
Perceptual, the most commonly used intent, will shift both in-gamut and out-of-gamut color to generate the best visual appearance for the image. Out-of-gamut colors are brought in gamut by closest color approximation to optimize colors for improved quality results in the destination display space.

Color rendering intent options.
Saturation Intent
Saturation focuses on the intensity of highly saturated colors in an image. Color accuracy is sacrificed for visual emphasis rather than accuracy. The saturation intent is an option for situations where pseudo color is preferable to realistic color.

Relative Colorimetric Intent
A popular alternative to perceptual intent, relative colorimetric matches color to color between a workspace environment and a destination environment to preserve color consistency. Out-of-gamut colors are changed to the closest in-gamut color, even when the shift involves duplicating a color that already exists. Workspace white is matched up with destination space white.

Absolute Colorimetric Intent
In gamut colors are mapped color to color. Out-of-gamut colors are remapped to best guess, in-gamut colors. Although relative and absolute colorimetric intents are similar when it comes to dealing with colors, they differ substantially regarding white. Absolute colorimetric treats white as a color that can cause a color shift in the destination space appearance of white, which may take on a warmer or cooler look.

Black point compensation preserves the relationship of blacks between the workspace and destination spaces. Dithering allows the conversion engine to combine in-gamut colors to best represent out-of-gamut colors.

Applying Standard Profiles

Adobe and other software developers provide a way to select and apply print profiles. In Adobe it can be done in the Convert to Profile dialog box, which comes with preset profiles for many standard destination devices and print surfaces.

Convert to profiles dialog bog.
Commercial printers and digital output service bureaus will provide information as to which profile setting to use for best results with their equipment. These system profiles have been worked out with developers and tested for predictability and consistency.Hardware manufacturers provide printer profiles that are available to be downloaded from the web. Downloaded files are usually installed automatically when opened.

Detail of destination space profile options.

Using Customized Profiles

The result of producing prints on a personal printer can be much less certain than in commercial production, however there are ways to print high quality color with unsurprising, dependable results.

Custom profiles can provide even better results than profiles that are available from manufacturers. What makes custom profiles superior to generic ones is that they use your own equipment and printing paper to take readings to generate a profile. So, if your printer’s inkjets are quirky; or you prefer to use third party inks; or you use hand manufactured or exclusive material papers like bamboo or canvas; or your livelihood depends on extreme color accuracy; you will probably want to order a custom made printer profile. There are several profile companies to choose from, like greatprinterprofiles.com, owned and operated by photographer Michael E. Gordon. Each provider has different instructions and applies different methods for generating a custom profile.

Creating a custom profile print usually involves these steps:
1) Make sure your monitor is calibrated.

2) Download and print out target pages.

Sample of greatprinterprofiles test target page.
Sample of printerprofilesonline target test page.

Sample of customprinterprofiles target test page.

3) Ship the printed targets to the profiling company.

4) When received, install the provided profile into your profile directory.

5) When an image is ready to print, follow printing instructions, and print.

Custom Color Profile Providers

In The Too Much Information Category

Many profiles are classified as ICC compliant. ICC stands for the International Color Consortium. ICC profiles are those that conform to the color standards of the ICC, which was formed in 1993. Many devices are set up using ICC standards. This is essential for consistent conversion from one color space to another. ICC standards can be applied to classes of input devices, display devices, and output devices. Algorithmic models perform the transformation between color spaces, for each device class. They work for device-dependent as well as device independent color environments. Here’s how ICC works. ICC operates in a “profile connection space” or PCS space. The PCS space provides an unambiguous interface between input and output devices. The interface is either CIELAB or CIEXYZ. These interfaces are based on tristimulus or RGB color values. The CIELAB system is based on a positive-negative, or push-pull, color relationship. And CIEXYZ is based on an X, Y, Z axis coordinate relationship of colors.