Chicago InDesign User Group Meeting Notes Archive
September 14, 2006
Hosted by Digital Bootcamp, Chicago, thanks to Mike Carruth, Commander in Chief.
Topic: Color Management
Presenter: David Sheffield, Photoshop geek and guru, freelance retoucher, Chicago
David Sheffield has been in the tech industry for years. I know because we started pretty much the same time, at The Rest of Us (TRoU) Mac user group way back when (OK it was 1986, I think). He is always an entertaining and knowledgeable presenter and he again lived up to his reputation when he tackled the subject of Color Management Systems (CMS). This is a thorny subject if there ever was one and for most designers, you say “CMS,” and the eyes immediately glaze over.
David started by saying that he is a CMS “practitioner” and not a “CMS consultant.” But he has learned a lot in the last few years and has put that knowledge to work for himself so that when he does his Photoshop retouching and compositing, his main livelihood, he can be confident that the color he sees on his screen pretty much represents the color that will come out on press—or at the very least, the color that will appear on his HP DesignJet color printer and in the large format output David gets from a variety of printers and proofers he owns. And that’s the bottom line, accuracy and predictability.
To start from square one, color passes from one device to another, such as an image that comes from a digital camera or scanner and then appears on a monitor and is finally output to a printer or press. Since each hardware device must interpret and translate the color, there is a conversion that occurs. The L-a-b color space is the go-between in that conversion. Lab is a “device-independent” color space developed in 1931 by the CIE, a group of color scientists who formed a commission to research and define a mathematical model of color space. As your color image passes through the workflow, Lab is the translator. RGB color in the camera image is converted to Lab color, the connector, then back to RGB for the monitor display. Then when printing, that RGB color is converted back to Lab and then again to the CMYK color that comes out of the printer. The “L” of Lab is luminance or grayscale. The “a” and “b” are the two hue spectrums with “a” defining the range between magenta and green and “b” between blue to yellow. Lab is also the native color space of Photoshop.
The problem with color is that color perception is so slippery. We’re dealing with RGB, the color system of light, often projected to a monitor, for instance, versus the reflected color of CMYK ink on paper. How do you make judgments about color when the various devices are so different in how they interpret color and use that color. And here’s where CMS comes into play. To have accurate and consistent color that you can count on, you need two things, David says:
- Monitor calibration—restoring the original RGB color values
- ICC profiles for your input and output devices
Calibrating and profiling are often done together, but they have fundamentally different goals. The purpose of monitor calibration is to restore your monitor’s color values back to the state when it came off the assembly line. While calibration is a key part of the CMS process, that alone doesn’t mean you necessarily get true color because each device puts its own spin on color and must be corrected to a universal standard of color. Ta-dah! Enter device profiling, the part II of CMS. A device profile is a piece of software that is specific to your particular make and model of digital camera, monitor, or color printer. It knows how to map color and correct those color skews. You might get that profile from the manufacturer, that’s common, or you might want to have one customized for greater accuracy.
What’s involved with doing calibration and profiling? An easy way to calibrate is to buy a “puck,” otherwise known as a colorimeter, for about $200-350, such as an Eye-One Display2 from X-Rite/GretagMacbeth, one of the longtime pillars of the CMS world. (http://www.gretagmacbeth.com/i1color). It attaches to the screen, takes readings and automatically creates a monitor profile. Good idea to let you monitor warm up for 30 minutes if you’ve just turned it on. If you also want to calibrate and profile all your devices, get a spectrophotometer. A handheld version cost $1400 about two years ago, David said. A good high-end solution is Monaco Profiler Gold or Platinum color management software, which lets you calibrate and profile your monitor, scanner and printer for $3000-5000.
As for profiling, although you can spend $100 for a printer profile from a service provider such as chromix.com, David showed how he builds a profile for one of his color printers. First he turns off all his CMS settings and makes a proof from a software “target,” which is a set of many small color swatches where the “correct” colors are “known” (absolute) Lab values. Then, by scanning each color patch on that page with a spectrophotometer, such as the Eye-One Pro, the CMS software can compare the differences between the printed and the correct known values and automatically build a profile to correct the printer’s color discrepancies.
Once you’ve got these two pieces in place, you’re almost there. But you also need to consider your physical working space. If you doing real Photoshop color correction work, not just layout, you need to follow some guidelines:
- No light directly hitting the screen. No glare.
- Ideally no daylight because you want an entirely consistent and neutral environment
- Background of your Finder or OS screen should be a neutral gray
Here’s a neat tip from David. You can get a “better” gray background to your Photoshop window by setting your Photoshop Color Picker to 130-130-130 RGB, then Shift-click with the Paint Bucket tool on the gray background of the Photoshop window.
When it comes to viewing printed color, the temperature of color is another important aspect of color management. Remember red is warm and blue is cool? Color temperature is measured in Kelvin degrees, where 5200° Kelvin is daylight and 3200-3400K is Tungsten, incandescent light. When you view printed color, it’s best to view that under 5000K lights for best accuracy in judging color correctness. Many printers have viewing booths with controlled lighting for just that reason. When you calibrate your monitor, an important part of that is setting the monitor’s color temperature. Whether you’re on a Mac or PC, it’s best to set the color temperature of your monitor to 6500K vs. 5000K, which tends to be too yellowish-looking. Additionally, most CMS consultants agree that a Gamma of 2.2 is better for on-screen “soft-proofing” purposes rather than Mac’s longtime default of 1.8.
Using Photoshop or any app in CS2, you can establish your Color Settings (Edit menu) and choose these industry-standard settings for a print workflow:
- Settings menu: North America Prepress 2
- Working Spaces (the color space for your application, not necessarily for your document)
RGB: Adobe RGB (1998)
CMYK: U.S. Web Coated (SWOP) v2
Save your settings to make them an external file (.csf). In Adobe Bridge, you can then synchronize your color settings across all CS2 applications.
Color management is a huge topic but I think everyone took away a clearer idea of how that world is composed and some of its key components. Thank you David!!
Resources:
The official CIE website
 www.cie.co.at/cie/
Calibration and profiling tools
www.gretagmacbeth.com/i1color
ICC profiling and lots of good CMS info here
www.chromix.com
More on CMS from Andrew Rodney, a CMS consultant and author of Color Management for Photographers
www.digitaldog.net
Books:
- Color Management in Mac OS X—a great book for entry-level reading
- RealWorld Color Management—excellent book, the bible for intermediate to advanced users
—The Chicago InDesign User Group meeting notes have been prepared by Eda Warren, Adobe Certified Training Provider and Adobe Certified Expert on InDesign CS2, http://www.go-training.com/. Thanks to David Sheffield for help with these notes.
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