Digital Printing – Color Space and Color Management

by Christopher B. Derrick

Color space, what is color space? Color space is the mathematical formula that sets the parameters for how a peripheral device displays color. Okay, now what exactly is color management? If you’re not asking this question, then you should.

It’s important to recognize and understand this element of digital photography because each device in digital photographic workflow – camera, scanner, monitor and/or printer – produces color differently. Color management is the process to get them all to act in harmony, so you can produce accurate and reliable images, over and over again. This is the bane to any one who’s done color printing. But you might also want to push the limits of your photographic pursuits as you might want to 1) improve the color matching between your monitor and printer; 2) use with fine art papers or nonstandard inks (i.e. archival pigment-based inks); 3) use a LightJet printer; and 4) reproduce color as accurately as possible for fashion, weddings, or art reproduction. To achieve these aspirations, you need to master color management. There is a steep learning curve, but once you know it you’ll love your digital darkroom all the more!

Each device in the digital image change can and will have its own color space that you can match to a reference standard or customize. There are numerous color spaces that we can talk about, but let’s take a look at the most popular standards.

Lab – This color space, which is really denoted L*a*b* (where L represents lightness and “a” and “b” represent opponent colors) is designed to approximate human vision, unlike RGB or CYMK, which are only formulas for blending light or ink. Lab color for all intents and purposes is an absolute color space, so it exactly defines a color. Lab also happens to be a color space that is more perceptually linear than the other color spaces and by perceptually linear; I mean that a specific reduction or increase of color value will produce a reduction or increase of about the same specific visual importance. The “L” nearly mimics human perception of lightness so it is most useful in making accurate color balance changes or to modify the lightness contrast. Lab space is much larger than the range of color available for monitors, printers and even the human eye, such that many colors that are created in Lab are actually imaginary colors (!) that we cannot perceive and cannot be reproduced.

RGB – This is the main color space that digital devices use to create the millions and millions of colors that we see in the real world and hope to reproduce as accurately as possible. RGB is an additive color model in which red, green, and blue light get mixed in various amounts to reproduce the colors of the rainbow (and everything else). The main purpose of RGB color space is to detect, represent and present photographic images in electronic devices (analog and/or digital), such a TVs, computers, digital cameras. It was also used in some forms of traditional analog photography. RGB is a device-dependent color space, in that each individual device that you are using senses or reproduces any given RGB value differently. Since the color elements (such as photo-diode pixels, liquid crystal or inks) and their response to the separate R, G, and B levels vary from manufacturer to manufacturer, or even in the same device over time, a standard means of controlling the uniformity of color reproduction is required… that’s the reason why color spaces are defined and controlled through color management. What this means in brass tacks terms is that an RGB color value is not the same from device to device.

Adobe RGB (1998) – In 1998 Adobe Systems, those creative suite masters, developed a RGB color, hence Adobe RGB. It was created to generate most of the colors achievable on CYMK color printers, but by utilizing RGB primary colors on a display device, such as your tube computer monitor (which is all they had back in 1998!), but also an LCD screen today. Here’s an interesting note, Adobe RGB is only able to reproduce roughly 50% of the visible colors that are achievable with Lab color space! In comparison to the original RGB, it has enhanced the cyan-greens.

Colormatch RGB – ColorMatch RGB, much like Adobe RGB (1998), is a relatively high-end monitor specific color space, which means that it’s designed for viewing on an electronic, light-emitting RGB source and geared for printing to photo paper. Because of this drawback, it suffers from something of a mismatch with your typical hard copy print out, particularly from a CMYK printing press or a photo-realistic inkjet printer. Colormatch RGB has a tendency have trouble reproducing the saturated yellows and oranges that you can achieve on photo printers. So if your photo images have lots of yellow and orange (maybe a snapshot of daffodils or an orange grove in the high season), you’ll have to resort to color space that has a wider RGB gamut to accurately reproduce those colors. ColorMatch RGB also clips (drops out) cyan, as well as the blues and greens that are situated next to cyan, and in some cases quite significantly. So it’s not really an ideal color space to use for effective color management.

Apple RGB – The is a color space that Adobe created for use on the mainstay Apple color monitor when Photoshop and Illustrator started to achieve prominence on the Apple platform. That Apple monitor is the classic Apple 13” RGB screen with a gamma of .8 and a white point a 6500 degrees Kelvin. It’s basically an obsolete color space, because many of the other devices in the digital workflow aren’t calibrated for that Apple monitor.

sRGB – This stands for “standard RGB” and it was created by the heady minds at Hewlett-Packard and Microsoft (so we can’t call it a monopoly) for a uniform standard color space for monitors, printers and… (drum roll, please) the Internet. Microsoft and HP wanted a specific color space with a wide enough gamut that would be ideal for typical home or office viewing, as opposed to those darkened rooms where hi-end color correcting takes place. As it was designed for the internet, sRGB has become the standard on computers, printers, many low- to medium-end consumer digital cameras and scanners, but it doesn’t have the wider gamut necessary for professional printing where you can tweak the color space calibrations of all the items in the work environment. Some might argue otherwise…

In any event, an image editing program like Photoshop enables you to change the color space at will for any image that you’re working with (be sure to save the original if you plan on doing this, because once you change color space you discard a certain amount of color information that can’t be reclaimed). Color space is extra crucial for ensuring that the same color values are reproducible across all the platforms in the digital print shop workflow (scanner, monitor, printer, paper). If you just intend on doing casual, every day viewing, then maybe you won’t care about color space issues. By why look at a photo that has inaccurate color? Even in the slightest bit.

Now that we’ve talked about the various types of Color space, let’s talk about getting everything in sync.

The first step along this long and windy path is the calibration of your monitor (because that’s what you’ll be looking at the most, so it should be your reference). Go into your monitor’s settings and set its color temperature (white point) to 6500K, D65, or sRGB, which is equivalent to 6500K. Then make sure the Monitor’s color depth is set to 24 or 32 bits. You’ll then want to adjust your contrast and the gamma to what is pleasing to your eye. You can save this calibration. Many monitors come with “preset” calibrations, these are the Monitor Profiles and they could Adobe sRGB, Adobe 1998, NTSC, etc.

The proper way to profile your monitor is to get profiling software and a spyder – a small spider-like device that attaches to your monitor that coordinates with the software to calibrate your monitor. This package enables you to find and set an objective Black point, white point and color balance. Now if you’re trying to make prints and you DO NOT calibrate your monitor this way, then you’re never gonna get what you want. A profiling package runs about 300 bucks, so go ahead and get one… you’ll thank me later, and every time someone compliments on the vibrant and accurate colors of your prints, you’ll thank me then, too. Remember, monitor profiling is only one part of the continual struggle, as a monitor’s characteristics drift and shift over time… so re-check the profile every 6 to 9 months to be on the safe side.

Once your monitor is set, you next have to calibrate your printer. There are two ways to do this, by using the print driver software adjustments or by using ICC Color Space Profiles. If you want to gamble and spent a lot of time, waste paper and ink, then you can fiddle with the print driver color controls. Remember you’ll have to do lots of test printing based upon what type of photo paper you’re printing on to ensure an accurate reproduction (most high-end photo paper has CYMK adjustment tags).

However, if you want to make accurate color photos, again and again, and feel confident that what you’re seeing on your monitor, or what you intend on scanning, will print with that same color space then use the ICC profiles (i.e. Adobe sRGB, Adobe 1998, etc.) such that everything can be synched and the discrepancies in color space are cancelled out.

The next thing you’ll need to do is profile your printer. Printer Profiling is the process of creating the specific profile that enables you to print the same way each time you use the printer and to have two printers perform with the same reference standards. To profile your printer you need to go into the Printer’s color profiling program and take out the spectrophotometer that you’re gonna need to buy that can interface with that profiling program, and go through the outlined steps. As you profile your printer, you’re setting the consistency and characterization of the inks, and calibrating the printer so it dispenses the ink uniformly.

A color profile is a dataset that tells the device what color space to operate in. This ensures that the vibrant red of Shania Twain’s ruby lips (see right) that you see on the camera and tweaked on the monitor appears that same way in the final print.

The real purpose of jumping through all the hoops of calibrating and profiling your equipment is so you can reach the promise land of digital printing: getting your photo to appear as a print as close as possible to what’s on your monitor. Soft Proofing is basically the process that enables your to see on your monitor what your final print will look like when it’s on paper… a specific paper.

Something that you do when you’re making the printer profile is set the color of the photo paper (it’s white, but what variation of white?). So soft proofing allows you to taken into consider various types of photo paper and ink combinations and how that will affect the final output. Now you understand why we went through all this profiling talk (it wasn’t to hear ourselves talk), because every photographer wants to know exactly how his final image will look – before going through the resource-intense process of making physical proofs…

Top image by HawkW

Chris Derrick is a writer, photographer, screenwriter and director living and working in Los Angeles. He studied film production and screenwriting at the University of Southern California, and continued to expand his photographic knowledge through classes at the Art Center College of Design.

Website: shadowboxercinema.com

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1 Comment

MiL said:

Thanks so much!!
I’ve a problem with the color managment in this pc. In web browsers, and interface, the white is white….but in image visors, and for example, photoshop, the white is a little bit “orange”.
And I can’t fix it, or I don’t know how to…
With this information, I understand a little more things about color, so I wish I can fix it now.
Very informative article!