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.