4.2. Calibrate and Profile Devices
As we've already noted, to calibrate a device is to bring it to a known set of standards (such as a color temperature and gamma setting). Once the device is calibrated, you can create an ICC profile in its calibrated condition. When the profile is used in a workflow, it can communicate its specifications from one device to another to yield consistent results.
Maintaining a machine in its calibrated condition is important for predictability of results over time. If a device shifts from its calibrated condition, the profile will yield inconsistent results, requiring recalibration. It sounds simple, and it is; even though some devices might require a more complex procedure, most devices are very easy to calibrate.
4.2.1. Basic Device Calibration
Here are the basics of device calibration for devices you may have in your workflow.
22.214.171.124. Calibrating digital cameras
Calibrate a digital camera by using a custom or preset white balance. Doing this will calibrate the camera to the lighting conditions and set a color temperature. Couple this with a good exposure, and you have the basic calibration needed for consistency. The challenge comes from the many varied lighting conditions in which you might be shooting. You may need to recalibrate the digital camera for each lighting condition.
126.96.36.199. Calibrating scanners
When you turn on a scanner, you can hear the scanner head moving across the bed (assuming it is a flatbed). The scanner is performing a basic calibration. Most scanners are able to calibrate themselves reasonably well. (Before scanning, you should thoroughly clean the glass of the scanner to minimize dust spots.)
188.8.131.52. Calibrating monitors
You have two choices when calibrating monitors. The first is to use a built-in, system-generated method of calibration. The second and more accurate method is to use a combination of hardware, a measuring device, and software such as the Eye-One Match software by GretagMacbeth.
GretagMacbeth Eye-One Match 2 interface
Macintosh system calibration tool for OS X
The operating-system-generated method is subjective and may not yield consistent results over time. Using monitor-profiling software, you will be asked which white point, gamma curve, and luminance value to calibrate to. If your monitor or display controls allow, you may select a color space, color temperature, or other controls that include individual color controls for red, green, and blue; brightness; and contrast, allowing you to optimize your monitor during the calibration procedure.
If your monitor does not offer some of these controls, you are better off with a software/measuring-device approach. Monitor-profiling bundles cost anywhere from $69 to $300 and beyond. With monitor-profiling solutions, the software will prompt you through the process step by step with explanations and diagrams.
A sensor will read a series of color patches on the screen to determine its current condition for color temperature, gamma, and luminance and will ask you to adjust monitor controls until you are as close to your set of preferences as possible.
As I mentioned at the outset, profiling a monitor is a two-step process in one session:
Let's take a closer look. Begin by turning on your monitor and allowing it to stabilize one hour before you start to calibrate.
Ideally, there should be no window light influencing your view of your monitor, as brightness levels, changing color temperatures, and overhead lights can affect how you see what's on your monitor. A monitor hood is an excellent solution in these conditions and can help keep ambient and stray light off the monitor.
First, decide on the white point for your monitor. For most workflows, 6500K is recommended because most monitors natively have this color temperature or close to it. However, many CRT monitors are set to 9300K (known as "TV blue") by factory default and need to be set to 6500K using the monitor controls. Most monitor-profiling software allows you to calibrate and profile the monitor using a native white point, which is the preferred method for LCD monitors or laptops. Another reason for using a white point of 6500K is that it matches fairly closely to a standardized 5000K light source, which is an industry standard for photography and graphic arts in the United States.
Once you have decided on the color temperature, you'll need to determine the gamma setting. The typical gammas that are available are 1.8 and 2.2. In the old days, Macs used a gamma of 1.8 and PCs used 2.2. Today, a gamma of 2.2 is best for both platforms.
I recommend a luminance setting of 120 for LCD monitors and 100 for CRT monitors. This setting is especially important if you wish to set multiple monitors to match each other as closely as possible.
GretagMacbeth Eye-One Match 2 Settings window
CRT monitors usually need to be recalibrated twice a month because they tend to change over time. LCD monitors are much more stable and need to be recalibrated only about once a month.
There are a number of monitor-profiling software packages and measuring instruments available. The Eye-One Display 2 from GretagMacbeth and the Monaco Optix XR from X-Rite come as a bundle. Others, such as basICCcolor Display, include only software and require you to purchase your own instrument.
184.108.40.206. Calibrating printers
Some printers have a means of automatic calibration or self-calibration built into their systems. Most ink-jet printers have utilities for head cleaning and print head alignment, which is a basic form of calibration. Higher-end ink-jet printers such as the HP 5500 have a measuring device built into the head to perform calibration. Other ink-jet printers that are supported by third-party raster image processors (RIPs) often include tools to calibrate or recalibrate themselves. The majority of ink-jet printers are relatively stable.
To achieve optimum results with an ink-jet printer, use the printer's utility to check the nozzles and print head alignment. This can usually be done from either the printer menu itself or a utility located in the driver. If the nozzles are not firing properly, you will see broken lines in the pattern created during the test. Select Head Cleaning to clear the nozzles. It may take several cleaning cycles in a row to fix the problem. If the heads are firing correctly and you see small horizontal lines on your prints, you could have a problem with head alignment. You can print out a different target pattern and see if the alignment is off. If it is, then it can be adjusted from either the printer menus or the print driver utility. Check the alignment whenever you install a new printer or move the printer to a new location.
Dye sublimation (dye sub) printer calibration is usually software driven. Some of these printers require you to print out a series of patches, select the most neutral patch (which is numbered) in the software, and type in the patch number in the window provided.
Most higher-end color laser printers have a means of calibrating themselves; however, lower-cost laser printers do not offer any means of calibration.
Nozzle check test pattern for an Epson 2400
Nozzle check test pattern after cleaning
Calibration is critical for consistent color because these devices drift due to temperature, humidity changes, and possibly the global political situation (or what I call mysterious gremlins). Some lower-cost color laser printers from Xerox have the option of calibrating with software called Phasermatch. You can adjust this software either visually or with a measuring instrument.
Many higher-end color laser printers have software RIPs, and some of these RIPs have a means of performing calibration with their built-in scanner or with a measuring device (see Chapter 5 for more RIP details).
Printing presses are very complex devices and are difficult to keep calibrated. Printers use a variety of different test targets and measuring devices to keep the press in control. Good printers will run their presses to industry standards such as SWOP or GRACOL. If you've ever been on a press run and watched the pressman calibrate the press, it takes sometimes up to 1,000 sheets (if sheet fed) to get the presses stable (or calibrated) for the run. Ultimately, the point is that every device, even the most sophisticated, needs to be calibrated.
220.127.116.11. Calibrating projectors
With projectors, similar with a monitor, start with calibrating projector controls: set the color temperature or a color space such as sRGB, or manually adjust it with the individual controls for red, green, and blue. Once you establish this base, you can then use a measuring device (such as the GretagMacbeth Beamer attachment for the Eye-One) for calibrating projectors to a selected white point and gamma setting. The contrast ratio, or dynamic range, of a projector is somewhat smaller than that of a monitor, so contrast range may be different from your monitor. But in most cases, the color can actually be very close to a properly calibrated monitor.
The GretagMacbeth Beamer, a projector calibration system
4.2.2. Creating Device Profiles
Once your devices are calibrated, the next step is to create a profile to use in your workflow. Profiles can be created for each device using profile creation software. You may choose to have a professional create custom profiles for you, or you can even download profiles from the Internet.
18.104.22.168. Profiling digital cameras
Digital camera profiles are created by first photographing a chart, such as this ColorChecker SG by GretagMacbeth (shown on this page). The lighting must be perfectly even across the chart and properly exposed, preferably by using a light meter to check the exposure. You'll also want to make sure the camera is properly white balanced. By entering this image (of the chart) into camera profiling software, you can create an ICC profile for the camera.
Note that this profile is best used in the lighting conditions that the chart was shot in. In my experience, I have found that camera profiles do not work for many situations. One of the many reasons that a profile won't work is that the target has a very limited range of colors compared to the real world. The software then tries to guess how the colors that lie outside the range of the targets should look. For this reason, in a majority of digital workflows, you would not use a digital camera profile per se. Instead, you might use the color space that the camera attaches to the file or manually select a working color space, such as sRGB, Adobe RGB, or ProPhoto RGB.
Adobe Camera RAW
ColorChecker SG by GretagMacbeth
Imacon Digital Back on Hasselblad
The Monaco Profiler, a scanner profile interface
Digital camera profiles do work much better in a fine art reproduction workflow because you are working with a narrower range of colors compared to the "real world." Sometimes these profiles need to be edited for different types of artwork, and that type of workflow is where custom digital camera profiles are primarily used today.
22.214.171.124. Profiling scanners
Because of the limitations of scanner software, you cannot calibrate or create profiles for all scanners. Some of the low-end consumer or business flatbed scanners fall into this category. If your scanner's software does not have advanced color management options, there are several companies (including Lasersoft) that make good software. You will need to check with these companies to see if they support your scanner.
To profile your scanner, use an IT-8 target, available as both reflective (color print) and color transparencies and made by different manufacturers, including Kodak, Fuji, and Agfa. If you plan on scanning transparencies and reflective materials, you will need to create an ICC profile for each separately.
Before scanning the target, you need to set up the scanning software using manual or advanced rather than auto mode. Locate the preferences or advanced color control options, and select the No Profile, No Correction, or Off optioneach interface is different.
Kodak IT-8 target
The GretagMacbeth Profiler 5, a scanner profiling interface
The ColorVision Spyder 2, a monitor calibration interface
Once the target is scanned and saved with no profile, you can then bring the file into a profile creation software application to create the scanner profile. In Chapter 5, Rick will cover a very comprehensive means of profiling scanners for a more advanced workflow.
126.96.36.199. Profiling monitors
When you create a profile for your monitor, the software will send a series of different color patches to the monitor. The software actually creates the monitor profile by comparing the color values of the patches displayed on the screen to the color values as measured by the sensor on the monitor. Using that data, it makes an appropriate adjustment to display color accurately. The first time you calibrate your monitor, the difference can be quite dramatic. Subsequent recalibrations will be less so.
Once you calibrate your monitor and have a monitor profile, the profile will be in good standing as long as you keep your monitor calibrated. So when you recalibrate your monitor on a monthly or bimonthly basis, there is no need to generate a profile each time.
188.8.131.52. Profiling printers
Profiles for some manufacturers are available online. You can also hire a professional color consultant to create custom profiles, or you can purchase the software and hardware to create them yourself, which is recommended. X-Rite/ Monaco, GretagMacbeth, and Colorvision offer excellent packages for creating your own custom profiles. These packages usually include the means to create profiles not only for printers, but also for scanners, digital cameras, monitors, and even projectors.
To create a printer profile with one of these packages, you must first print a chart of color patches. The software interface will give you step-by-step instructions on which chart to use and how to read the patches with a device known as a color spectrophotometer. Once the patches have been (properly) printed and read with the device, the software will give you options for creating the profile for a particular viewing or lighting condition.
When you're printing these color patches from Photoshop, make sure your Photoshop Color Settings have been established properly, as we discussed in the last section. Selecting the option "Leave as is (don't color manage)" will keep the values of the target native, which is critical for creating the profile. In Photoshop, select File Print with Preview. You will see "Profile: Untagged RGB in the Print area, and using the Color Handling Options pull-down menu, select No Color Management. This again will keep the values of the target native. It is also important to print the file at 100% to keep the patches at the proper size for the spectrophotometer. (It is okay to resample the file before printing if necessary to make the image prints large enough.)
After you select Print, leave Photoshop and go to the print driver. Select the printer that you are creating the profile for; in this example, we will use the Epson 4800. There are two areas that are critical to configure: the Print Settings, where you choose your media type, print quality, and printer resolution; and Printer Color Management where you select Off or No Color Management, ensuring that these patches will be printed in their native state. Note that although the print driver interface looks different on a Mac (where you have drop-down menus) than it does in Windows (where you have tabs and an Advanced button), the options are the same.
The following are three important steps for using the print driver in a color-managed workflow:
Anytime you change these settings in the print driver, you are affecting the color. Be sure to use the exact same settings for each media that you create a profile for. Also, note that you will need to create a separate profile for each distinct resolution.
In order to avoid having to go through all the options in the printer driver each time you print, you can save settings as a Preset once you have created a (or use any) profile (from the Presets pull-down menu, select Save As). When saving the preset, make sure you use a naming convention that is descriptive: include information such as the printer, paper, and resolution. Keep the name short so you can see the whole name in the Presets window, as I've done here by naming it 4800PremLust1440.
Print the target and check for any problems, such as marks, lines, or scratches. Because inks need to stabilize, allow the inks to thoroughly dry before measuring the patches. Fifteen minutes is good for pigmented inks; however, the surface may take three or more hours to cure and become resistant to surface scratches, etc. A dye-based print may take up to 24 hours for the patches to stabilize and cure.
Reading the patches with your measuring device should be pretty straightforward; just follow the steps provided in the user interface. Your software will want to know which set of patches you've printed before starting, and then, depending on the device you're using, patches will be read with either a patch-by-patch, strip-by-strip, or completely automated (hands-free) method. After you have read in all the patches, the software will inform you that you have been successful. When you close the window, you will be prompted to save the data.
X-Rite, Pulse Elite System Output Profile interface
Before the final profile is generated, it is important to select a viewing light source. D50 is a known standard lighting in the U.S., but if you are viewing under other lighting conditions, pick the one that is closest to what will be used. (If unknown, choose D50.)
ProfilerMaker Pro 5 (GretagMacbeth) gives you an option to "Correct for Optical Brightener," which becomes available if the paper that you are using has an ultraviolet optical brightener to make the paper appear whiter. To make the paper appear whiter, the UV brightener white is actually made more blue, which needs to be compensated for. Some spectrophotometers have a UV filter on them to prevent this problem. If you encounter a paper with a UV brightener and your measuring device does not have a UV filter, this option to correct will be available, and you should select it.
You are now finally ready to save your profile. Give it the same name as your measurement data so that you don't become confused. The next step is to use this profile to produce a great print, as we will discuss in stage 3 in the next section.
GretagMacbeth ProfilerMaker 5.0 interface for printer profiling
And surprisingly, these profiles are becoming more useful in many kinds of workflows. Each manufacturer offers its own brand of paper, which has been optimized to work with its inks, dyes, or chemical processes. For ink-jet workflows, there are papers and even inks that are made by third parties to work with these printers. Some papers may not absorb the inks properly, and the color may not reproduce correctly, which would necessitate creating your own profile or obtaining one from the supplier, if available.
184.108.40.206. Profiling projectors
Projector profiles are created at the time of calibration. If your projector is stationary, one profile can be used over a long period of time. The same profile can be used by other computers that may use the same projector and screen. For projectors used at various locations and lighting conditions, create a profile for each location.
4.2.3. Editing Profiles
You may need to edit your profiles to adjust for anomalies for a given deviceperhaps open up shadows, add or subtract a percentage of color, etc. Doing this is similar to editing images in Photoshop with the profile creation software packages, as mentioned in this chapter. The illustration shows X-Right Monaco's Pulse interface for profile editing. (For much more on editing profiles, see Chapter 5.)
X-Rite Pulse Elite System profile-editing interface