When you process and print digital photographs, you want the colours and shades in your prints to come out looking exactly the same as the image you see on the screen. As many of us know to our cost, this isn’t something you can take for granted. Monitors and printers create colour in entirely different ways. A monitor illuminates red, blue and green pixels with a white backlight; a printer creates colour by mixing different inks or pigments on paper.
Problems arise when your monitor settings don’t reflect the way your printer produces colours. For instance, a monitor with the wrong white balance will add a colour cast to your images when they’re printed – and you won’t spot that anything is wrong until it’s too late. Your monitor’s colour settings can trip you up even if you don’t print out your images: things that look perfect on the screen aren’t guaranteed to look right on someone else’s.
It isn’t only a question of colour fidelity. Modern monitors typically leave the factory with their brightness turned up to maximum. However, prints rely entirely on subtle reflected light. When you process an image to look bright and vivacious on your screen it might still result in a dull, flat print.
The solution is to calibrate your monitor so that it displays colours as accurately as possible.
There are two approaches to calibration. The most accurate is hardware calibration, in which you attach a colorimeter to your monitor while a series of tests is run. The colorimeter measures the colours your monitor is displaying, and produces a monitor profile that gives the best colour accuracy the hardware’s capable of.
The second approach is to use software to measure your screen’s performance. This isn’t as accurate, but it’s still an effective approach – and if you have a modern PC it needn’t cost a penny, as Windows 7 includes a reasonably advanced calibration tool as standard. It relies on good visual acuity, but it’s better than nothing (see walkthrough on Page 3).
Photo-editing software can adjust an image’s colour balance, but without an accurate monitor profile you can’t be sure how it will print.
No matter how you calibrate your monitor, it will never perfectly represent the printed product. Some high-end printers can produce a greater range of colours than a monitor, so it’s possible to end up working with colours that can’t be distinguished on your monitor and only become visible when you hit “Print”. However, calibration will keep unpleasant and potentially expensive surprises to a minimum.
No monitor is perfect
You wouldn’t expect a cheap LCD panel to be perfect, but if you spend a packet on the latest premium monitor – precisely because you plan to use it for photography – you might expect to gain only a marginal improvement in accuracy through calibration.
This isn’t the case. Monitors leave the factory with a number of default settings; we mentioned brightness above, but contrast and colour saturation can also be pumped up to the maximum. These settings are chosen to grab your attention on the shop floor, but they’re enemies to colour accuracy (and, in some cases, taste). If you’re viewing an image on a monitor with too much contrast, you’ll have to reduce the “punch” in your image to get it to look right on the screen. The printed version will come out looking drab.
If you invest any serious time and effort in your photography, calibrating your screen is a must. If you’ve also invested serious money in your monitor, setting it up properly will ensure that the cash hasn’t gone to waste (for more on why you should calibrate your monitor, click here).
Setting up your monitor
Before you begin delving into calibration software or hardware, it’s important to understand the idea of the “white point”. This is normally described as a temperature, measured in Kelvin, and is a setting you can adjust on your monitor to set the overall tint of your display. A high Kelvin measurement (some monitors are set to around 9300K) means your monitor will display whites with a slight blue tint, but you’ll probably never have noticed it: the human eye is very good at ignoring colour casts.
For photography, you want a more neutral white point: 5000K is close to the neutral white light of the midday sun, while some photographers swear by a 6500K setting. These options are normally accessible via your monitor’s onscreen display. If your monitor doesn’t provide Kelvin settings, less formal nomenclature such as “Neutral” might be used instead. A hardware calibrator can be useful here, as it can detect a neutral white balance.
A screen calibrator can provide an accurate picture of your monitor’s performance. Here it compares a monitor’s colour reproduction to the sRGB gamut.
The onscreen appearance of your images doesn’t depend solely on your monitor settings; the environment in which you edit your photos is just as critical. Incandescent household bulbs emit a very warm light, which affects your perception of colour and explains why monitors compensate with a bluish colour temperature.
A bigger concern is the quantity of ambient light around your monitor. If your computer is in a room with lots of light, it’s likely your monitor’s brightness will be turned up to keep things legible. That’s good for visibility, but it means you’ll be processing your images on a monitor that’s excessively bright. The result? Prints that are too dark. The ideal photo-editing environment is one with neutral lighting, closed windows and closed blinds. At the very least, this is the environment in which you should set up your monitor. A hardware calibrator will also be handy here, since it can detect both the luminance (brightness) and colour temperature of ambient light: a useful guide as to whether you’re on the right track.
When to calibrate
When you come to calibrate your monitor, don’t do it immediately after turning on the display. An LCD’s brightness comes from its backlight – a series of bulbs that light the red, green and blue pixels that form the image on screen. Most monitors are lit by cold cathode fluorescent lamp (CCFL) tubes, and these can take a while to warm up to their full brightness. For this reason, before calibrating your monitor or doing colour-sensitive work you should allow your screen to warm up for around 30 minutes. Attempting to calibrate a cold monitor is an exercise in futility. The exception to this is monitors lit by LED bulbs, which reach full brightness as soon as they’re turned on.
CCFLs also start to lose their brightness as they get older. This means that, over time, your monitor will become dimmer and the colour temperature will slowly rise, ultimately producing images that appear warmer than they should be. This means calibrating your monitor isn’t a one-off operation. Monitor manufacturer Eizo recommends recalibrating a screen once every 300 hours of use. On monitors used during normal working hours, this equates to roughly once every two months; monitors used at home and recreationally will need less attention.
If you’re using Windows 7, the built-in colour calibration tool can be a big help in getting your monitor set up correctly (see walkthrough, p3). Those on older operating systems – and without the inclination to splash out on dedicated hardware – needn’t despair, though. It’s still possible to make an educated guess as to how your monitor needs to be corrected, and you can normally do it for free using tools included in your graphics card drivers. These typically let you choose your own settings for brightness, contrast and gamma, the latter of which controls the lightness or darkness of mid-tones. It’s best to make these alterations here rather than using your monitor’s onscreen display (OSD). Most LCDs don’t offer the ability to set gamma, and some prevent you from changing contrast.
When you adjust these settings, the driver usually displays a reference image so you can see the effect of your changes. If you prefer, you can use a reference image of your own. A simple way to do this is to print out a photograph with a reputable professional printer (www.photobox. com remains a firm favourite at PC&TA), hold it next to your monitor, and look closely for differences. It’s best to use images of people: the eye can be tolerant of variations in abstract colours, but you’ll be able to spot an incorrect skin tone from a mile away.
It’s then simply a matter of making the required adjustments. For example, if the final print looks fine on screen but too dark when it’s printed, turning down your monitor’s brightness will help images look the way you want.
NEXT PAGE: Understanding colour spaces, ICM profiles explained.
Understanding colour spaces
Adjusting your monitor according to a single printed image will bring its colours into line with that particular printer, but it doesn’t guarantee that your images will appear on other people’s screens in the same way as they do on your system, nor that they’ll look identical on all printers. To achieve this, you need to be aware of colour spaces.
A colour space represents all the shades of colour available to a device. The two colour spaces you’re most likely to come across are sRGB (standard red, green, blue) and Adobe RGB. Of the two, Adobe RGB offers a wider gamut, which is to say it can represent a wider range of shades. When you shoot JPEG images on a DSLR camera, you’ll normally have the option of using either the sRGB or Adobe RGB colour spaces. Depending on which you choose, the colours seen by the sensor will be encoded in slightly different ways. (If you shoot in RAW mode, the camera uses its own, far larger colour space, and leaves you to perform your own conversion when you process the image.)
Mid-range monitors lit by CCFL tubes rarely display the full range of colours in the Adobe RGB space (high-end LCDs, especially those with LED backlights, can produce a wider gamut). However, if your monitor is correctly calibrated and your editing software understands which colour space was used to encode an image, you should see a reasonable onscreen approximation of the appropriate colour. Mid-range and high-end printers are also normally designed to support a wide gamut, so it makes sense to use Adobe RGB for images you want to print.
If you want to share your images online, it’s a different story. Most web browsers ignore colour-space data and assume your images should be shown as sRGB. This can cause them to look subtly wrong: for example, the Adobe RGB space offers a smoother transition from yellow to green than sRGB. If you view an Adobe RGB image using the sRGB colour space, the contrast between these colours will appear exaggerated.
To add to the confusion, most mid-range and high-end printers can produce colours not covered by either the Adobe RGB or sRGB colour spaces. It’s therefore possible that your images will contain shades of colours that are indistinguishable on your monitor, especially if you work in the ultra-wide ProPhoto RGB colour space favoured by Adobe’s photographic software. In most cases this won’t produce unpleasant surprises when you print, but if you’re concerned about the detail it’s worth producing colour proofs before committing to expensive, large-format prints.
A final word to those looking to produce books or other unusual formats: print services will sometimes expect you to provide images in CMYK format, in which colours are produced by combining cyan, magenta, yellow and black ink. CMYK represents a much smaller colour space than sRGB and Adobe RGB, so colours from your original image may need to be “clipped” to match those within CMYK’s gamut. Applications such as Photoshop allow you to soft-proof your images using different colour spaces, and can warn you if large areas of your images contain out-of-gamut colours.
What are ICM profiles?
After calibrating your display, your settings will be saved as a “profile” – an ICC (International Color Consortium) or in Windows an ICM (Image Color Management) profile. The two are largely cross-compatible. Windows Vista and 7 also support a proprietary Microsoft format called WCS (Windows Color System).
A monitor profile specifies how the colours and shades described in an image file should be sent to your monitor to ensure they look correct when displayed. For example, if your monitor produces unusually weak-blue shades, a suitable profile would tell the operating system to compensate by boosting the blue content of the picture it sends to the display.
Calibrators measure ambient light as well as your monitor’s colours, so you can see whether your environment is too bright or warmly lit.
Printers also have profiles, althoughmodels aimed at home users don’tnormally come with tools to calibratethem. Just like monitor profiles, theseprofiles tell the software how toproduce colours that look as intended.
With the right monitor and printerprofiles, colour hues should lookidentical whether you’re viewing themon screen or on a physical print-out. Ifyou use an inaccurate ICM profile – oryou don’t create one at all – coloursmay be lost or mistranslated, resultingin wonky prints.
Correctly setting up your monitor istherefore essential if you don’t wantto waste time and money on sub-parprints. And getting your screen onthe right track is quick and easy. Evenprofiling your monitor using dedicatedhardware is reasonably cheap (seeHardware calibration, above). If youwant to get the best from your digitalphotos, there’s no reason not to do it.
NEX PAGE: Step-by-step guide to profiling your monitor with Windows 7.
Walthrough: Profiling your monitor with Windows 7
Make sure there are no light sources shining on your monitor and give your screen30 minutes to warm up. Ensure it’s set to its native resolution. When you’re ready,you can reach Windows’ colour management settings through the Display option inthe Control Panel: look for “Calibrate Color” in the bar on the left-hand side. [Click on pic to enlarge]
Before you start adjusting software settings, set your monitor’s brightness to maximum and choose a neutral white point. Monitors use a frustrating variety of ways to describe white points, so you may need to consult the manual. A neutral white point is around 5000K or 6500K; many monitors ship set to 9300K. [Click on pic to enlarge]
The next step is to set your monitor’s gamma. Too high and images will be washedout; too low and you’ll lose detail in the shadows. It should normally be set to 2.2, butWindows’ calibration tool doesn’t give a numeric measurement. You can get close byadjusting the slider until the dots on the screen blend in with the surrounding area. [Click on pic to enlarge]
Windows makes finding the right brightness and contrast settings simple. Using the sample images, adjust the settings until you’ve produced a good facsimile of the reference image. Some monitors don’t let you adjust the contrast if the screen is hooked up to your PC via a digital connector such as DVI or HDMI. [Click on pic to enlarge]
Next you need to find a neutral white point for your monitor by adjusting the levels of red, green and blue. Juggling the bars can take some time, not least because moving one often means you’ll have to move another to compensate. This step is very important, as it will ensure you’ll see an accurate display of colour on your screen, so it’s worth the effort. [Click on pic to enlarge]
The final screen shows you the before and after versions of your monitor profile – and the Color Management panel provides more options. You can view all the colour profiles associated with your monitor, as well as profiles for printers etc. The All Profiles tab shows all the profiles installed, useful if you need to add a profile for an external printer. [Click on pic to enlarge]
Although Windows 7’s calibration tool is free and easy to use, dedicated hardware will do a better job. When you use calibration software, you’re relying on your eyes to make decisions about contrast and brightness. There are two problems with this. First, different people perceive colour and brightness differently, introducing a significant margin of error. Second, the apparent brightness of your monitor will depend to some extent on the lighting in the room – which in turn is affected by the age of the bulbs, the amount of light coming through the window, and a host of other factors.
LaCie blue eye pro Proof Edition
Hardware calibration devices are inherently more accurate, and because they attach, limpet-like, to your monitor screen, ambient light isn’t a factor. However, some calibration software, such as GretagMacbeth’s i1Match software (www. xrite.com), can also measure the colour temperature of ambient light, which will give you another significant accuracy advantage when it comes to your editing environment.
Hardware calibration doesn’t have to be expensive. LaCie’s easy-to-use Blue Eye Prois at the top of the scale at around $400, but you can get hold of devices such as Pantone’s huey colorimeter for less than $150.