how to calibrate a display.
Do prints made from your digital camera match your display (monitor)? Unless you're display is calibrated, chances are they don't. This article explains why, and how to match things up.
Every display, regardless of cost, displays color somewhat differently. Arbitrarily adjusting the controls on a display for contrast, brightness, and other settings only makes matters worse. This isn't much of an issue if all you do is word processing... if you've adjusted your display so its appearance is pleasing to you, that's great.
But if you use your display for digital imaging that involves people and equipment on the outside world -like sending files to DigiGraphics for printing- your display needs to be calibrated so that it displays color according to a standard. For color to reproduce as expected, from display to print for example, both display and printer must conform to a standard. Such a standard exists; it was developed by the International Color Consortium (ICC) for the purpose of defining and translating color as accurately as possible from device to device.
A common mistake is adjusting a display by eye, to match some form of printed output (we call this 'chasing prints'). When this is done, the printed output -no matter how good or bad- is treated as a standard. This may work with some degree of success in a closed-loop workflow where your printed output is done on equipment under your control (an inkjet printer for example). Unfortunately, this method falls apart as soon as your image takes a trip outside the office for professional output like that produced at DigiGraphics.
This is why calibrating a display to a standard is so important, and why we don't chase prints by adjusting a display to match printed output. If every display used for digital imaging was calibrated and the results were understood, we'd never again hear the question, "Why don't my prints match my display?" When the display-variable is taken out of the equation, we can be certain that if prints don't match it's because of something other than an un-calibrated display.
Calibrating your display is the first and most basic step required to insure that what you see on screen and in print are close to each other. If you use DigiGraphics, or any other professional print service running calibrated equipment, you must have a calibrated display in order to predict with any certainty how your files will print. Fortunately, of all the things we tweak and prod in our cameras, computers, and software, calibrating a display is one of the simpler things to do. Here's how it's done:
First, you'll need a calibration package consisting of a USB hardware device that measures how your display displays color, and the software that runs it. Several companies make these packages, costing between $80 and $280. The two most popular devices are the "Eye One" by X-Rite and the "Spyder" by ColorVision. Doing an internet search will help you decide which device is best for you. We use the Eye One to calibrate our displays at DigiGraphics.
DigiTip: Software-only calibration programs such as Adobe Gamma can be used for rudimentary calibration. These programs aid in setting brightness, contrast, and color temperature by displaying several color patches and asking you to make selections such as 'which patch is warmer', '...cooler', etc. While this procedure is probably better than nothing, it relies on the subjective nature of human vision, which is not only easily fooled, but each individual's perception of color is unique. If you are serious about accurate, predictable color, there is no substitution for a professional calibration package.
Basic visual calibration tools include items like the following graphic which includes 11 blocks ranging in tone from solid black to solid white. If you are unable to make out all 11 tones, adjust your display for brightness and contrast until all 11 tones are visible.
On many un-calibrated displays, the first two or three blocks on the left appear to be the same tone. On others, the box at far-left is too light for a solid black.
DigiTip: If you're not ready to purchase your own calibration device, but would like to perform an initial calibration on your display, ours is available for 24-hour rental. We also offer a 1-hour, 1on1 tutoring session that includes calibration of your display. Depending on the stability of your display and the level of accuracy you demand, an initial calibration may remain accurate for a week to several months or longer.
Once the calibration software is installed, calibration begins. The program asks a few questions about your display and viewing preferences, then guides you through a few manual settings. A series of color patches is displayed and measured by the USB device. The measurement information is used to construct a table that compensates for inaccuracies in the display. The finished result is an 'ICC profile' that's used by the computer to display color properly. The profile is automatically loaded when your computer is turned on.
Because displays change over time, calibration on a regular basis is necessary. Depending on your display and the accuracy you demand of it, calibration may be necessary once a week, or once every few months. The displays we use at DigiGraphics are typically calibrated every 15 days.
Post-Calibration: Understanding what you see. It is important to understand what you can expect from calibrating your display, and the reasons why you will observe some differences even after calibration. Even with a perfectly calibrated display, and prints made from a calibrated printer, there will be some differences when direct comparisons are made between the two.
This is due to a number of factors, including the fact that all displays are different. High end graphics displays are designed and manufactured to display color with greater accuracy than typical office/consumer displays. Typical desktop and laptop displays have certain limitations which cannot be completely overcome through calibration. That said, all displays benefit from calibration. Some just benefit more than others.
Even with the best graphics display, there is a significant difference between the appearance of light emitted from a display, and light reflected off a print. It is much the same thing as viewing a slide on a light table and comparing it to a print of the slide. No matter how close they are, they are inherently different in appearance because they are two completely different materials, illuminated in two distinctly different ways.
With experience you'll learn to mentally compensate for these differences, much the same way you compensate for the difference in appearance between the camera's viewfinder (everything looks great in the viewfinder!) and prints that are made. Rest assured, if you could compare prints against the viewfinder, you'd be stunned at the difference in appearance between the two.
We're accustomed to accepting this difference, and it's no different when dealing with the differences between a display and print, except that the display, unlike the viewfinder, IS available for comparison... so we need to be smart about our analysis of the differences we see, which differences can (or should) be corrected, and which ones can not.
Because of the differences between a display and a print, and the way that the human visual system works, it is important to view and compare in the correct way. Objective comparisons cannot be made by holding a print directly next to the display. Rather, the print and display need to be in different fields of view so they are viewed individually, not simultaneously (see photo below). This is easily accomplished by placing the print off either shoulder, at a right angle to the display. We do this for a variety of reasons that go beyond the scope of this article, but the simple reason is that the eyes need a moment to adjust when moving back and forth between display and print. If the eyes are not allowed to adjust, you'll be led to believe that certain differences exist between the display and print which are, in fact, visual illusions.
Photo: Proper right-angle viewing setup between display and print.
The viewing environment has an impact. When making a direct comparison between a display and a print, the color temperature and intensity of the light reflecting off the print is not likely to match that of the display. If your display is set to a color temperature of 5500 Kelvin, and your office lights measure 4500 Kelvin, the prints will appear warmer, or more yellow in comparison to the display. Going a step further, the color of the walls and amount of sunlight in your office all have a direct effect on the color reflected off a print. Color temperature between the display and the viewing environment do not need to match, and quite often professionals prefer different temperatures for each. The reasons for this will be discussed in a future article.
If there is a marked difference in density (brightness) between print and display, there are a couple of possible culprits: The room lighting is too low, or the display is too bright. LCD displays have a tendency to be overly bright. If room lighting cannot be brought up in intensity, then the display should be recalibrated to a lower intensity (or luminance) until a suitable match is obtained. Our LCD Apple Cinema Displays are calibrated at a luminance level between 70 and 80 CD/M2 (candelas per meter squared). The calibration software allows you to set luminance according to a target value which you define.
When all is said and done, it's important to understand that the goal is not to produce a print that perfectly matches the display -which is not physically possible- but to provide a match that is close enough for you to predict what printed output will look like. In the end, we want a print that stands on its own. It's the print that will be displayed on a wall, not the computer display. People will not be looking at your prints and asking to see what it looked like on your display!
When analyzing the final result, it's best to take a critical look at the print -all by itself- and ask if there is anything you would change to make it more perfect. If the answer is no, you're golden, regardless of what's seen on the display. If the answer is yes, then it's time to return to the display and make critical adjustments to the image... using the display as a guide to help you predict and hone the final printed result.
The whole point of calibrating is to reduce variables which are under our control. To the extent that we can do that, we achieve a workflow that is as predictable as possible. Understanding the variables that are out of our control (or not practical to control) helps us to mentally compensate for certain differences, and hopefully, keeps us from running back to the display and arbitrarily twisting knobs in an ill-fated effort to find a perfect match that will never exist...!
DigiTip: Once your display is calibrated, any changes made to its controls (brightness, contrast...) voids the accuracy of the calibration. If your display is used by others, it's a good idea to let them know. And too, some displays have controls that are all to easy to adjust by accident. Our Apple Cinema Displays have touch-sensitive controls which are easy to 'touch and adjust' by accident. We cover the controls with a small piece of cardstock to avoid accidental adjustment.
So calibrate! You'll stop seeing red over greens that look yellow!