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DCR Workshop: Color Management, Part II
by David Rasnake -  5/4/2008

In Color Management, Part I we dissected basic concepts of color management as they relate to profiling and calibrating displays. It's a new month, and as promised, we're back for the second part of our color management series, in which we'll explore the process of profiling a printer's output in order to match what you're seeing on your screen with what you're getting in print.

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As before, we'll also be checking out the print-related portion of Datacolor's Spyder3 color management system, the Spyder3 Print, and using this tool to demonstrate the process of profiling a specific printer, paper, and inkset.

(As an aside, if you haven't checked out part one of this series, I'd recommend taking a look before proceeding further, as many of the concepts outlined are carried over into printer profiling.)

With all of that in mind, let's get started.


PRINTER PROFILING 101

Once you understand the premises set forth in the first article and the basic technologies at work in making your screen output match your printed output, understanding printer profiling is comparatively easy. The basic idea is the same as monitor profiling: referencing a pre-defined standard shared by all of your system devices, a printer profiling system creates an ICC profile which adjusts your printer's output so that the colors line up with standardized values. Assuming your monitor is also profiled and calibrated, the output from both monitor and printer should be nearly identical (when the monitor references the printer's profile to limit its gamut – more on this momentarily).

RGB to CMYK

In order to create this profile, the color management system has to have some output from your printer to reference, as well as a way to analyze it. Getting a reference output – essentially a "test print" – for analysis is easy enough: at its most basic, the color management system asks the printer to print a test chart consisting of color blocks (called "patches" in the world of color management) that, depending on the size of the chart and the number of patches, more or less comprehensively cover the entire spectrum of the printer's output.

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Each patch in a chart of this kind represents a known color value, specified as an RGB value (that is Red, Green, and Blue, the same system for referencing color that monitors use). Pure black, for instance, has an RGB value of 0-0-0, and pure white has a value of 255-255-255, with 255 being the maximum possible value. Pure blue, then, would be specified in RGB as 0-0-255. Most real colors in the real world contain some mixture of all three color values.

To oversimplify somewhat, in a normal printing situation, your printer's print driver is tasked with taking the RGB values from an image that you're printing from your computer and converting RGB colors to equivalent values that can be rendered by the printer's inks, which are usually Cyan, Magenta, Yellow, and blacK (or CMYK). Just as a computer's graphics card renders colors based on formulas supplied a profile via the LUT, the print engine renders colors from RGB to CMYK based on a similar profile that it references.

Spectrocolorimeters

Thus, all the color management system needs to do to create a profile for a printer is compare how the printer prints a certain RGB value, or a series of them, with an accepted standard for how that particular color or series of colors should appear. Just as with monitor profiling, this in turn requires a piece of hardware that lets the software "see," in essence, what the printed output looks like. Enter the spectrocolorimeter.

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A variant of the same principle that powers the more basic colorimeter we used to profile the monitor in part one, a spectrocolorimeter is essentially an electronic eye capable of measuring color off a printed page and reading it out as an RGB value.

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By comparing the actual RGB value of each patch on our test chart to what the RGB value should be according to the accepted standard, the color management system can make determinations about how the printer is rendering color and adjust it accordingly.

As a fairly specialized piece of technical equipment, spectrocolorimeters were once prohibitively expensive, and a very precise one for professional print or scientific applications can easily cost thousands of dollars. While a spectrocolorimeter will probably still be the most expensive piece of a color management system (sometimes more expensive than the printer itself even), prices for consumer and basic professional-grade devices have come down to the point that they are within the reach of essentially all working professionals and many advanced amateurs.

Inks and Papers

Of course, the kind of ink a printer uses, whether it's OEM or a specialized aftermarket product, as well as the paper being printed on all have a potential impact on the final color output. For this reason, profiling is a process specific not only to a particular printer, but to a particular paper and inkset as well.

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While there's some leeway in how much of an impact using different papers makes – two high-gloss paper of a similar weight from the same manufacturer will often print accurately with a shared profile – to maximize the effectiveness of profiling, a specific profile should be built for every inkset and every paper used. The differences between how a gloss paper of one brand holds ink and how a matte paper from another maker performs with the same ink lay can be enormous, and these differences in the paper's base color and coating and how it responds to ink ultimately impact the final color, tone, and density of the image. This, of course, means printing the required test chart or charts with the paper and ink being profiled: without consistency in this area, you can't expect output results to be consistent.

Hardware-Specific Issues and Soft Proofing

Making sure that the appropriate profile for the selected printer, ink, and paper is being referenced is tricky business, made trickier by differences in operating systems, print drivers, and color management practices in specific software packages. Even more so than with monitor calibration, then, it's impossible to generalize a single best practice for setting up a color management system given these differences.

Associating a specific profile with a certain paper type/group of setting usually isn't difficult in the print driver menu (it wasn't in the case of the Canon printer used for this test), though those working out of advanced programs like Photoshop often prefer to have Photoshop's print engine reference the specific profile and manage colors. One of the advantages of Photoshop or similar programs over many consumer-focused printer drivers is the ability to specify "rendering intent" – in essence, how the monitor's gamut gets mapped to the destination profile (more on rendering intent in the next section). In our tests and experience, whether you choose to use your image software or your print driver to handle color management, you can get accurate results either way: it's more about finding a setup that works with how you work.

Beyond simply associating the profiles, there's a specific process that provides an even more accurate tool than monitor profiling and calibration alone can offer for visualizing how your images will look in print. Because of differences in gamut and in the way colors are rendered, color profiles for printers will never translate directly from monitor colors (though they'll be much closer with profiled output on both sides). Getting a truer simulation of what you'll be seeing in print is accomplished through a process known as "soft proofing." Most photo editing software (and even some print drivers) can show you a soft proof of your image based on whatever printer profile you select; check out the documentation provided with your specific photo editing system for more info on this.

When you first open a print for soft proofing, you'll probably be shocked at how washed out it looks: the colors are correct in terms of hue, but usually much less saturated. This is fairly typical – a result of the fact that a good LCD can provide a level of color saturation that even a good printer isn't capable of reproducing across the color spectrum – and it should be noted that a print on paper doesn't necessarily look as washed out as the screen (with its high maximum saturation levels and luminance) suggests. This under-saturated appearance does suggest, however, that you may not be getting as much dynamic range out of your prints as your printer is capable of producing. To this end, using the soft proof function to observe the impact that different adjustments to an on-screen print have on the final printed output, you can often find the dynamic range limits of your print output. A slight curves adjustment, for instance, can often bring back a lot of the saturation and contrast to the soft proof, and thus, to the print. Don't forget that you may want to maintain two versions of an image file: one that's adjusted for ideal color and range on-screen (the first step), and a second print version (often just a second layer in the same file, if you're working in Photoshop or similar software) that's optimized according the soft proof view.

Budget Options

Finally, as with monitor calibration there are some low- or no-cost alternatives to a full-on print color management system that can form some great first steps, at least, in color management and help you explore the effects of profiling your printer output without jumping head-first into some costly (and not always novice-friendly) accessories. Most printer and paper manufacturers provide pre-built profiles that can, in many cases, provide results nearly as accurate as a custom-built profile. Paper companies, especially, often provide these resources for download via their websites, making them a great resource to play around with if you don't mind using a little paper. Similarly, several companies will build extremely detailed profiles for your specific device, ink, and paper based on prints you send them – for a nominal fee, of course.

As the option requiring the least initial financial outlay, most print drivers also allow fine-tuning of the print output with basic adjustments like hue, saturation, contrast, and ink density. If you can afford the paper you'll use up in the process and the time it takes to get things just right – this is, after all, where the real cost of the manual method comes in – a little trial and error with these controls can often go a long way toward making your default profile much closer to what you're seeing on your monitor.


PRINTER PROFILING TOOLS

If you're exploring the idea of building your own printer profiles, you'll quickly discover that, not surprisingly, the same group of players – led by X-Rite and Datacolor – that inhabit the monitor profiling space work in this part of the hardware and software world as well. Also not surprisingly, the software for the job is occasionally integrated with monitor profiling packages; as in the case of the Datacolor system we looked at, even if the packages aren't integrated into a single software, the interface, commands, jargon, and processes are very similar for related systems from the same manufacturer. Of course, in light of the fact that the profiles created are common file types handled not by the color management software but by the graphics and print drivers, there's no reason why you can't choose one manufacturer's system for one side of your process and a different maker's device and software for the other side to get the combination of features you're looking for (though there may well be arguments against it in some cases, related more to profile proclivities in terms of color management than to compatibility issues).

While separate hardware for profiling displays and printers is still more common, X-Rite recently made a splash with its affordable (sub-$500) ColorMunki profiling tool that uses a single spectro and software interface to handle a range of profiling tasks. Of course, there's honestly little advantage or disadvantage either way for general users in the one device versus two debate: as with many purchases, choosing a setup that fits within your budget, has the features you need, and has an interface that communicates on your level (after all, the least useful profiling tool is the one that doesn't get used at all) should the three primary considerations.

For consistency's sake, we're again combining the how-to portion of this piece with the chance to look at and evaluate the other component in Datacolor's Spyder3 system, the Spyder3 Print. As before, the walk-through that follows deals specifically with the Spyder3 Print system, though the process is much the same whatever hardware and software package you choose.

Installation and Configuration

Installing the Spyder3 Print software on either a PC or a Mac takes less than a minute, start to finish. The basic installation doesn't even require a restart for PC folks, and the installation menu is exactly the same as the Spyder3 Elite software.

Right off the bat, Spyder3 Print prompts the user to perform some basic printer setup steps in order to assure consistent print orientation and minimize paper waste.

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After a basic welcome screen, the Spyder3 software asks for some basic information about the printer, ink, and paper being profiled.

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Most fields are self-explanatory, though the starred "Driver Media Setting" box deserves a bit of attention: if your printer has a predefined setting for the particular paper type you're profiling, it's a good idea to go ahead and fill in that information exactly as the printer/print driver presents it. (In this case, for instance, Canon's "Photo Paper Pro" medium already has its own profile in the drop-down list of paper types that appear in the printer driver.) Supplying this piece of information will help the Spyder3 system automatically associate the color profile it creates with an existing general print profile from the print driver.

If you don't opt to skip straight to profiling at this point, the software encourages a couple of basic print checks to make sure everything is in working order with the printer.

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As suggested, it's also a good idea to check your printhead nozzles before launching into printer profiling, just to confirm that the printer is consistently laying down ink. Many printers provide some kind of printhead test procedure, usually accomplished by printing a test page; check your printer's manual or driver software if you're not sure how to perform a check and cleaning on your specific device.

Alternatively, if you know that your printer is ready to go, you can skip these prompts altogether by clicking "Skip to Printer Profiling" from the Printer Definition screen.

As a rule, I found the Spyder3 Print setup to be somewhat less intuitive than the process for configuring Datacolor's related monitor calibration and profiling tool. There's less "hand holding" and prompted guidance with Spyder3 Print, and the software makes some assumptions about your knowledge of your setup and your printing preferences – probably not unreasonable assumptions, however, given the Spyder3 Print's target market (the box does say "Designed for Professional Photographers," after all...).

Printing the Target

At this point, the user is asked to specify how many patches the software should sample in creating the profile. Obviously, more patches equal more accuracy, but also take much longer to print and longer to sample. The three basic options are the "Fast Target" (150 patches), the "High Quality Target" (225 patches), and the enormous and intensive "Expert Target" (729 patches on three sheets from a standard sheet-feed printer, or on a single large sheet for plotters).

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For creating a basic profile, the 150-patch target provides more than info, though users looking for more accuracy can jump in to the larger targets if desired. While they're more time-consuming, the process is the same, and thus there's really no penalty for working with a larger target right from the start.

Once the type of target is selected, it's time to print the target from this screen (using the "Print Target" dialog). Again, remember that you'll need to print the target using the specific printer, ink, and paper that you're creating a profile for.

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After a brief drying period to allow the ink to set, we're ready to get down to actually profiling the output.

Setting up the Spectrocolorimeter

This is where the real work begins, and anyone planning to undertake the process of measuring a test chart should block out at least half an hour or so (if you're working with the larger 225-patch chart, especially) to allow ample time for taking measurements and prevent hasty mistakes.

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Before launching in to the measuring process, the spectrocolorimeter itself must be calibrated.

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This is fairly easily accomplished by placing the spectro into its base (which has a white calibration tile that sits beneath the optical element) and clicking the device's action button.

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Note that getting the spectro connected and recognized by the software is usually as easy as simply connecting it to the computer. I did have a little difficultly in the PC interface making the spectrocolorimeter register with the software. It took repeated disconnecting and reconnecting to get the USB-driven device to show up in the Spyder3's sensor list.

With the spectrocolorimeter connected and calibrated, Spyder3 Print will prompt the user to create a file for storing the spectro's measurements.

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Unlike with some of the prompts seen earlier, the name used here is completely arbitrary – just pick something that will be easy to identify if you use multiple printers and papers (and especially, multiple printers or papers of the same brand).

Reading the Patches

After walking the user through the process fairly thoroughly up to this point, when it comes to actually measuring the target instructions and tips are a little sparse. Thankfully, patch measurements in Spyder3 Print are all displayed on-screen, providing an easy to follow visual guide for the measuring process.

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Each patch is measured in turn (moving left to right across each row, and down the page from top to bottom) by holding the spectrocolorimeter over the specified patch, highlighted on the computer's target display.

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Though Datacolor doesn't provide much help in using the alignment rail and spectro, the system is fairly intuitive. The rail helps align the spectro's "eye" over the row of patches being measured, allowing the user to slide the spectro down the row to measure each patch. The spectrocolorimeter fires a burst of light for taking the reading and hence doesn't require any ambient light on the sensor. In order to take the most accurate reading possible, it's advisable to go slow in order to make sure the spectro head is properly aligned and sitting flush against the page (thereby keeping ambient light off of the sensor).

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With the device aligned over the specified patch, taking a reading is as simple as clicking the spectro's top-mounted action button. The Spyder3 software provides a confirmation sound almost immediately (each reading takes less than a second), letting the user know that the reading has been taken. This process is repeated patch by patch, row by row, until the entire chart is read.

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As before, we've provided a video walk-through of the measurement process:

 

For the smallest test target, measuring all of the patches should take less than ten minutes. Spyder3 Print prompts the user when the process is finished.

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Building a Profile

From this point forward, the process is largely automatic. Using the measurement file created in reading the patches (or any other measurement file, selectable from a drop-down menu), Spyder3 Print builds a profile.

As with the Spyder3 Elite system, Spyder3 Print uses the SpyderProof image matrix to give an idea of how different kinds of shots will print using the newly created profile.

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Soft proofing can be toggled on and off via the checkbox, and the four basic rendering intent options all appear in a drop-down menu.

For more technical comparisons (to a printed target, for instance) or to examine the limits of the profile's gamut, clicking the image matrix while holding down the CTRL key brings up a 225-patch test chart.

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That's all there is to it: the profile is created and available for use.


THE RESULTS

As with the first part of the series, the impact of profiling our test printer was, when compared to its unprofiled output, subtle yet visible.

Color Analysis

With the Pixma printer used for this test, I was particularly unhappy with the saturation of reds. Even after repeated adjustments, driver tweaking, and so on, I could never get the vibrant pure reds that I was seeing on my screen from the printer when working with glossy photo stock. Even with some pretty serious hue shifting, the results in this range were almost invariably too cool/pink. This is one area where profiling had an immediate impact, with the difference between saturated reds showing clear improvement after profiling. A little fine tuning of the soft proof and my "fire engine" reds were nearly as shiny and vibrant as what I was seeing on my screen – and, for the first time, in the same tonal family on both display and print output.

This particular example ties up the larger point nicely: profiling may not eliminate the need for trial and error work, but given the visual reliability of soft proof results, it gives you a no-print (and hence, no-cost) way to do trial-and-error fine tuning. The fact that colors from an accurate profile are almost invariably hue accurate (even if they aren't always correct where saturation and contrast are concerned) means that strange color skews – which can be time-consuming to correct, given that fixing skewed colors in one range often shifts them further in another – are largely eliminated.

What equally impressed me in the final analysis of the Spyder3 Print is just how much the prints look like their soft proof variants. With a well-tuned workflow, it's not hard to get soft proofing that is, for all intents and purposes, dead on when compared to printed results. This is also where the sample size really comes into play, as I saw what could fairly be called a clear difference in color accuracy of some of the more subtle "problem values" (light greens, purples) after rebuilding the profile using the expert target.

Spyder3 System Performance

A few final words on the Spyder3 system: I particularly appreciated the interface carry-over between Spyder3 Elite and Spyder3 Print. While it might have been nice to see both packages integrated into a single front-end control for users running both the display and print systems, the familiarity of the interface from one side to the other made finding adjustments and anticipating the software's requirements that much easier.

Compared to a series of pre-built profiles for different papers that we tested it against, the Spyder3's printer/paper profiles were, not surprisingly, more color accurate and appreciably more neutral. Whereas many of the canned profiles we looked at seemed to build in an image tone, the Spyder3 was, to my eye at least, extremely middle-of-the-road in its profiling approach, producing prints that tended to have somewhat less added punch and saturation by default, but that were also more fair representations of the soft proof.

The Fine Print

As has been said throughout this series, there are myriad hardware and workflow variables that all impact the end results of the process when moving from on-camera images to in-hand prints. I've been intentionally selective throughout this series in presenting information in a way that hopefully won't overwhelm new users, but simultaneously gives a fair and thorough explanation of the color management process. As always we're glad to field color management questions related to specific setups or systems in our discussion forums. Whether you're a beginner wanting to learn more about basic color management or an advanced shooter looking to iron out wrinkles in your workflow, we're glad to continue the conversation and expand the scope of this discussion in that venue.


CONCLUSIONS

Providing a level of flexibility previously attainable only with much more expensive equipment, color management systems are at once a better deal than ever and yet still not cheap. To get both parts of the system we looked at here – employing the Spyder3 Elite system I used to calibrate and profile my displays in Part I (ca. $270, street price) and the Spyder3 Print tools used here ($500) – you'll have to lay out a whopping $770 (that's roughly the cost of the new Canon Rebel, just in case you needed a reality check) for the convenience of knowing that you can reproduce exactly what you're seeing on your screen in print. As noted, there are cheaper options on the market than our slightly more advanced Spyder3 combo setup, but even for a bare bones system you'll be spending $400 or more to profile both printer and display.

The flipside, of course, is that if you make a lot of prints, or you want to make a lot of prints, you probably don't have the time, energy, or, in the long run, the money to spend hours in post-processing, only to have to spend more hours tweaking and reprinting to get the print looking like the post-processed image on your screen.

While the Spyder3 Print system works well, is fairly intuitive to use, and offers a fair amount of flexibility for its price, those looking to enter the world of color management can still get progressive improvements in their results and workflow by breaking the investment down into steps that are a little more financially manageable. For casual printmakers, a monitor calibration and profiling system, some canned printer profiles, and a little time spent manually tweaking your printer output is an easy first step that will make an impact and only takes the cost of the much less expensive monitor system to implement. Remember, monitor profiling and calibration is the baseline from which the rest of your color management system is built – profiling a monitor without profiling a printer makes much more sense than the converse.

Ultimately, Datacolor's complete Spyder3 system has proved to be a powerful companion to our color management walk-throughs, suggesting (as has been said before in this series) that with the big players offering some great new products, now is a better time than ever to get into color management at the consumer level. If the process itself is involved and takes years to master in its nuance, the tools and software for color management definitely aren't scary. Color management is one of the keys to the digital darkroom, and taking charge of the process can unquestionably save a lot of headaches down the road if you print lots of images.