The Ideal Room With A View
The environment in which we view a finished printed product is a piece of the color management puzzle too often overlooked. When holding a printed piece of paper in your hands, it is easy to think that it's the end of the story. Yet, the light used to illuminate that print is a vital component of how the color on the page is perceived. If you doubt me, take that print into the closet with the light off, and then tell me what color it is!
Let's review some basic color theory. When we see color, we are seeing light waves from a light source bouncing off of a surface and reflecting into our eyes, where our brains interpret these signals as colors. Rather than thinking that the object itself is the source of its color, it's vital to remember that the color of the object is largely dependent on the light waves striking the object to begin with.
One of the reasons we so easily take color and light for granted is because of chromatic adaptation.
Chromatic adaptation refers to the way our eyes "white balance" to the light source in our environment. Not merely a fun term to throw around at cocktail parties, chromatic adaptation is essential to understanding how our eyes view objects. Our eyes are not merely biological spectrophotometers that see and determine color. Our brains do an awful lot of automatic, subconscious color correction. Without chromatic adaptation, we would have a mess of a time trying to recognize consistent hues across different lighting situations.
30 years ago, just about every home was lit by traditional tungsten light bulbs, which give off a warm, reddish/yellow light. No one noticed it as red unless someone happened to take a picture indoors, without a flash. The picture would come back from the film processor with a very warm cast. If something similar happened in an office environment, the pictures would come back with a green tint. Nothing was wrong with the processing of these pictures: they were actually a perfect example of how dramatically chromatic adaptation works within the human brain. The photographs were showing what the environmental lighting actually looked like as recorded by the daylight balanced camera film; the reason they appeared different than expected was because individuals' perceptions were, unbeknownst to them, affected by chromatic adaptation. Similar experiments can be done with the manual settings on a modern camera with white balance turned off. Chromatic adaptation enables us to move between different lighting sources and see them as "normal."
In this day and age, your environment's light sources are even more varied. Besides the remnants of tungsten and F1 fluorescents that still remain, there are halogen lamps, fluorescents, and of course, LED lighting options in all shapes and colors. While our eyes and brains easily adapt to these different lights, artificial lighting can hide or exaggerate subtle color issues when we're taking a serious look at prints.
This dilemma is why viewing booths were invented. Color-critical workflows require some kind of controlled, verified space where you can trust that printed output is viewed in correct light. These booths or stands come in various sizes so you can place large or small printed material within and be assured that the light you're viewing is an accurate representation of the color, which is usually standardized to D50 daylight. Since the adoption of ISO 3664, viewing booths also include a consistent amount of UV light so these booths can more accurately imitate natural daylight. The print and graphic arts industry tends to use D50 as its standard illuminant of choice. D65 is a slightly cooler version of daylight that many in the textile and manufacturing world prefer.
Optical Brightening Agents
A few decades ago, Optical Brightening Agents (OBAs) were rarely used in printing. As the desire for brighter paper has become more commonplace, it became necessary to update the international color viewing standard. Since OBA paper is becoming more commonplace, the lamps used in viewing booths have been updated to contain a specific amount of UV light to more closely match what we get from the sun. UV light is what triggers the brightening and bluing of OBAs. A modern viewing booth will allow the viewing of a print in a manner that effectively imitates natural daylight. Proofing papers with a similar level of OBAs have also been developed, as have the press papers they proof; thus, everything works in tandem provided you use a viewing booth which supplies UV light.
The Ideal Room With A View
To do this right, you need a proper, fully-enclosed light viewing booth with a size proportionate to the prints you need to view. The room must have no exterior windows, which could bring in uncontrolled light sources and interfere with accuracy. The lamps in a viewing booth ought to be ISO 3664-compliant and within the 2,500 hours of use recommended by the manufacturer. The walls of the room would be painted with a neutral gray, non-reflective paint. Those in the room ought to wear neutral-colored clothing. While this may seem like overkill, the color of the walls and the people around the viewing booth can have a definite effect on the way a color is perceived. Oh, and the people making the color decisions would be female. (Women tend to have more accurate color discernment than men.)
Your immediate thought might be, "This all sounds good, but I just cannot afford a $3000 light booth."
Fair enough, but at least you now understand the need for one- that's a start! Apart from the ideal scenario described above, compromises are available. For instance, desktop viewers which start at about $500 may be closer to your budget. There are also a few do-it-yourself options. This said, be wary of consumer lamps that promise a certain Kelvin temperature on the label; they are not designed for professional color use. If you have a spectrophotometer that can take ambient light measurements, you can use this to confirm whether or not your lighting environment matches the advertised claim. CHROMiX has used SoLux lamps for many years and has had good results with them.
The overarching idea is to create a controlled environment with light as close as possible to D50 daylight. Minimizing strong colors in the nearby environment will also increase accuracy and reliability.
Other environmental concerns
We have written in the past about how the color of the walls, floor, and peoples' clothing, can make a difference in how human observers see color, and can even affect instruments in some cases. Consider, for example, a client of ours who was having a lot of trouble calibrating a display in a challenging environment. The equipment was working fine, but the result of the calibration always showed a red tint on the display. With some troubleshooting, they discovered that the strong red carpet in the conference room reflected light onto the face of the display, which was reflecting into the aperture of the colorimeter during its calibration.
If you're interested in learning more about this, we have also written about how a white or dark border around a print can make the image appear lighter or darker.
This is further evidence to the point that any strong color in your environment has the potential to throw off your "unbiased" perceptions.
Getting your Printer to Match your Display
Whenever we talk to folks about getting a printer and monitor to match, we often begin by changing the monitor. It is easy to change a few settings, recalibrate, and have the display produce a different color and brightness. Controlling the lighting under which you view your prints is the other half of the puzzle. Because it involves more work and is likely more expensive, this part of the puzzle often gets neglected. We recommend creating an ambient environment wherein the white of your paper is as close to D50 as you can reasonably make it. Get your illumination to D50, set your display to match the white of your paper, calibrate the display with a modern colorimeter, and you've done all the heavy lifting required to get your prints to match your display.
While the perfect viewing room might not be attainable for all of us, anything you can do to improve your viewing conditions and remove conditions that might contribute to viewing biases, will make your world a safer place for color.Thanks for reading,
Further reading: http://www.colorwiki.com/wiki/Metamerism_Article