Plugged In: Calibration — Color me accurate

By Joe Kashi, for the Redoubt Reporter

“What you see is what you get” has long been the norm for imaging and word-processing programs, eliminating nasty surprises where the printed final output doesn’t match what you saw on your computer monitor. Until recently, most digital photography was far more hit or miss.

Consistent and complete calibration is the key step in precision photography, ensuring that what you saw when you took a photo is also what your end viewers will see, whether as a final print or on a computer screen. It’s also key to reducing wasted and expensive supplies.

This week, we’ll examine the many factors that affect the appearance of your photographs and how to control these factors through careful calibration of each step of the photographic process. This is a somewhat technical but important topic, so we ask your indulgence and attention.

Careful calibration has always been key to good photography. During the film era, Ansel Adams’ “Zone System” was the best-known approach to reliably making high-quality photographs that accurately reproduced the photographer’s intent. In the digital era, it’s just as important, but easier and more affordable. You’ll not need to repeat precision calibrations very often but, over time, they’ll avoid a lot of wasted effort.

You’ll need some specialized hardware and software to calibrate accurately. Eyeballing camera and computer screens, then making guessed adjustments is neither accurate nor repeatable.

It’s no secret that most digital cameras interpret colors and brightness levels differently from each other, particularly when making JPEG files directly in the camera. It’s also no secret that most digital SLR cameras may not focus as precisely as we’re led to believe.

That brings us to our first step — calibrating your cameras. Where possible, I’ll first go into a camera menu system and set as my “color space” AdobeRGB 1998, a generally accepted color standard that reproduces a much wider color range than the usual “sRGB,” which somewhat crudely approximates how the average uncalibrated computer monitor displays colors and brightness.

Using AdobeRGB throughout your photo process, from camera through monitor calibration and post-processing software, helps maintain repeatably accurate results. Although there are other, arguably better, color spaces, AdobeRGB 1998 has one major advantage — it’s natively supported by most top-end cameras and software.

Then, using X-Rite’s Color Checker Passport software and standardized color charts, I’ll calibrate each camera under a variety of seasonal daylight and indoor lighting conditions. This software automatically profiles how each camera actually responds to standard colors under various lighting conditions and then stores each profile where Adobe software can find and use them when displaying your images. Give each profile a descriptive name when saving.

While taking photos, the overall “color” of the light affects how images appear. Our eyes and brain interpret a wide variety of lighting conditions far more neutrally than digital cameras and monitors. Although the auto color balance found in modern digital cameras is usually fairly accurate, it’s not very precise. Most Alaska photographers know that the color and hue of our natural daylight varies a great deal from summer to winter, with summer light, shadows and cloudy days all tending toward bluish tones, while winter light often appears very yellow to brown in digital images. Although your eyes and brain are fooled, your camera isn’t.

Most color balance problems can be readily corrected toward more neutral, accurate colors in post-processing software, such as Photoshop and Lightroom, using the “eye-dropper” color balance tool. Finding the right spot for color balancing tools and exposure correction can be a problem, though. There’s an inexpensive and useful device to solve that problem — the SpyderCube, a small cube that provides a neutral white surface for color balance and pure black, 18 percent midgray and bright specular highlight surfaces that are useful when correcting exposure, contrast, dark areas and highlight areas. Hang the SpyderCube near the edge of your photo in the same lighting conditions, take a photo or two with it included in the frame, and your later correction of color balance, contrast and exposure will be much easier.

Accurate autofocus is crucial to achieving maximum sharpness with every lens. Setting accurate autofocus on a dSLR camera also requires a specialized tool, in this case, the Lens-Align II. Not all dSLR cameras allow you to adjust where they actually focus, so before buying this tool, check your camera’s instruction manual and determine whether you can even adjust its focus response. Most higher-end dSLRs allow focus calibration.

Our next step involves calibrating your computer’s monitor. Most monitors are basically uncalibrated, or only very approximately so. You should assume that virtually all low- to mid-range monitors are set for the most basic color space, sRGB. Some excellent high-end monitors, like the Dell U2711, ship with a choice of pre-calibrated color spaces, usually sRGB and AdobeRGB 1998. Assuming that your camera is already set to Adobe RGB 1998 color space, then if possible also set your monitor to that color space. What you see should be a fairly reasonable approximation of the image as captured by the camera.

The biggest problem is that most monitors are set at a very high brightness, or “luminance,” level, too bright to reliably match any final print. Our brains adjust our vision to counteract this excessive brightness but our hardware cannot. Moreover, our eyes also adjust to the overall brightness, lighting and wall color of the room in which we view our monitors, further complicating how we see what’s displayed on our monitors.

As you might guess, the first step is to view your monitor under unchanging light conditions and to shield it from other light. When critical color and luminance adjustment is necessary, I’ll also view my monitor with the room’s florescent lights turned off so that my eyes adjust to what’s displayed on the monitor without as much interference from my surroundings.

Although some operating systems and monitors claim to allow direct calibration using only the monitor itself, this is unreliable, at best. I’ve found that X-Rite’s ColorMunki, hardware-based measurement system is the most reliable approach to calibrating not only how your monitor displays photos but also how closely your final print matches what you saw on your monitor. Here’s how to use it:

Use the ColorMunki to first measure the brightness of the room in which you print, setting your monitor’s brightness as needed. Then, run the complete color and luminance calibration routine using the ColorMunki measurement hardware.  The entire monitor calibration process takes about 10 minutes or less. The included X-Rite software will then build a profile of how that computer and monitor displays colors and brightness levels, programming your video card to automatically set itself to calibrated standard values. Because most monitors change brightness and color values as they age, you’ll want to repeat this fully automated calibration process every month or two for repeatable results.

In some ways, printers are both the easiest and the most difficult devices to calibrate. Every printer reacts differently to various combinations of inks and printing papers. Printer manufacturers know this and publish downloadable “profiles” that adapt how each printer model reacts to a particular type of photo paper. When you set your photo software to use a particular printer and paper profile when printing an image, you are actually instructing the printer how to deviate from its default settings in order to adapt to that printer-paper combination and make the best possible print.

That’s the theory, at least. In practice, though, most profiles are approximations for an entire printer line and many of the best photo papers do not have accurate profiles. The best and most cost-effective solution is to make your own printer-paper profiles using the ColorMunki’s highly automated printer profiling function.

Before every serious printing session I’ll first re-profile my Dell U2711 monitor and then immediately profile the printer that I plan to use. That’s done by printing standardized patches of bright colors, measuring them with the ColorMunki, and then printing a second set of subtly colored patches and again measuring them. The resulting profiles are named appropriately and automatically stored where they are visible to all Adobe photo programs, although you’ll need to instruct Adobe which new printer profiles should be displayed as choices.

Make a few test prints and verify their appearance under the actual lighting where they’ll be displayed. You’ll need to make any subtle final adjustments by hand as you view the test prints under the actual display lighting.

Profiling and calibrating your printer to your monitor is the final link in the process of precision photography and the technical quality of your images should improve noticeably.

Local attorney Joe Kashi received his bachelor’s and master’s degrees from MIT and his law degree from Georgetown University. He has published many articles about computer technology, law practice and digital photography in national media since 1990. Many of his technology and photography articles can be accessed through his website, http://www.kashilaw.com.

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