The answers to every question you've ever asked, wanted to ask, or didn't even know you were supposed to ask ...
What is a monitor calibrator?
It's a small hardware device that you place on your screen to perform the calibration process.
They vary in size and shape between brands, but loosely speaking they're about the size of a mouse. They are USB-powered, and come with software to control the process. They function equally well on both Mac and PC (I'm not aware of any calibrators that only work on one platform).
What is monitor calibration?
What we commonly refer to as "calibration" is actually two consecutive processes - "calibration" and "profiling". This distinction is important.
The "calibration" part happens first - that's the part where you (with the guidance of the device) physically adjust the settings of your monitor as required. The amount of available control varies widely between monitors, so in some cases the "calibration" part of the process is negligible. I'll discuss this further shortly.
The "profiling" part happens next - that's where the device reads a series of colours displayed by your screen and records a description of its characteristics. This description is called the "monitor profile". Then, colour-managed programs (such as Photoshop, Lightroom, some Operating Systems, etc) refer to that profile when displaying colours, in order to achieve colour accuracy.
Of these two processes, the "profiling" part is more important; and it's the one which can't possibly be achieved by the human eye. It might be possible to roughly "calibrate" your screen just by looking at it, but "profiling" requires colour sensitivity that we simply do not possess.
For the purposes of simplicity, I shall hereinafter refer to the combined calibration/profiling process as "calibration" (except where the distinction is relevant to the point at hand).
Why is monitor calibration necessary?
If you've ever been in a television store and watched the same movie being played on a whole wall of televisions, you'll know how colour can vary from screen to screen, model to model, and brand to brand.
You calibrate your screen to bring it into line with a central standard. That way, the colour you see on your screen (brand "A") should be the same as the colour I see on my screen (brand "B"), and the same as another photographer sees on their screen (brand "C"); and most importantly, of course, the same as your printing lab sees on their screen.
A brief history of monitor calibration
Up until not many years ago, we used a rudimentary "closed loop" colour management system. That is, we clumsily adjusted our screens in a vague attempt to make them match the print. And if we switched to a new lab, or if our lab got a new printer, or hired a new operator, or whatever, then we'd have to get more test prints made, and start adjusting again. Needless to say, this was a futile and frustrating process. Surprisingly, some people still persevere with this.
The modern system is infinitely better. Now, we all adhere to a central standard, as I mentioned before. We don't match our screen to the lab, we simply match it to the central standard, and expect the lab to do the same.
Does monitor calibration guarantee print accuracy?
No, not quite. It's certainly a very important step towards print accuracy, but there are other factors involved as well. I've written more about this here.
I can give you one guarantee, though ... if your screen is not calibrated, you've got slim hopes of print accuracy.
How important is it for photographers to have calibrated screens?
Consider heart surgery for a moment. The most important facet of heart surgery is undoubtedly the surgeon themselves - their enormous intellect, their steady hand, their dedication. Also very important are the surgical tools that are used.
But on the bench at one side of the theatre is more critically important equipment - sterilisation equipment to keep the surgical tools free of contamination. If an unclean scalpel causes an infection, the surgeon's good work is ruined.
When it comes to photography, you are the most important facet - your vision, your creativity, your execution. Your camera, lenses, lights, and software are also important. But if you work on an "unsterilised" screen, all of that can be ruined.
Think I'm exaggerating? I'm not.
Can all monitors be calibrated?
Yes. All monitors are capable of being adjusted by a calibration device, to at least some degree, and with at least some degree of improvement. Some screens (eg laptops) have fewer physical controls than others, so the process is more heavily weighted to "profiling" than "calibration"; but laptops certainly can, and should, be calibrated.
Of course, not all screens are genuinely suitable for editing photos. Cheap screens with narrow viewing angles are a nightmare to edit on, for example. Make your next monitor purchase wisely.
How often should calibration be performed?
Monthly, is the usual advice. Some high-end retouchers recalibrate every morning, but that's unnecessary for most of us.
The colour on CRT monitors used to drift like leaves on a pond, especially as they aged, so weekly calibration was not uncommon. But modern LCD screens are much more stable, as a rule.
Is monitor calibration easy?
I won't lie to you - some people have trouble with it for one reason or another. There seems to be a universal failing among calibrator manufacturers whereby they don't include enough instructions in the box. However, the companies all have Help Desks, and there are plenty of resources on the internet.
But generally speaking, yes, the process is quick and easy. It will take the longest time when you first perform it, of course, but then subsequent monthly calibrations should be a matter of only a few minutes.
Will you see a big difference after calibration?
That depends entirely on your screen. Some screens (especially Macs) are pretty good from the factory, so the difference will be negligible. Other screens (particularly the cheap ones) are quite blue in their uncalibrated state, so you'll notice a considerable difference.
Actually, when you first calibrate, you mightn't like it. If you've grown used to your very blue/bright screen, it may seem too warm/dull to you at first. I urge you to give it a chance. Even after 24-48 hours, you'll probably be used to it, and wonder how you ever tolerated it so bad before!
Does monitor calibration guarantee colour accuracy in all software?
No, only the colour-managed ones.
Programs like Photoshop, Bridge and Lightroom automatically detect and utilise a monitor profile, so you don't need to worry about anything. Some programs need you to manually point them to the profile in order to be properly colour-managed (Canon's Digital Photo Professional is one that springs to mind).
Other programs are simply not colour-managed at all. That is, they wouldn't recognise a monitor profile if it bit them on the toe. I'm talking about the cheap image viewers such as Microsoft Picture Viewer, etc.
Web browsers vary. At the time of writing this article, Firefox and Safari are colour-managed, but Internet Explorer is not. (If you are devoted enough to your photography to be reading this long and boring article, you should definitely be browsing in Firefox or Safari, at least until Microsoft see fit to colour-manage their product).
So, you're likely to see a difference between images in Photoshop and Internet Explorer, for example. You may be assured that Photoshop is correct (assuming you haven't messed around with its Color Settings).
Monitor calibration and the internet
Monitor calibration means everything, and nothing, when it comes to the web. Let's face it, 99.9% of people who browse the internet are doing so on uncalibrated screens. So you can't possibly expect many people to see the exact colour in your images that you would like them to see. Don't lose any sleep over it - there's nothing you can do. Just be reassured by the knowledge that Mr and Mrs Public don't know much about colour - they just like looking at your photos.
So does this mean that monitor calibration is pointless when preparing web images? Of course not. It's still vitally important that you edit your images on an accurate screen, and post them on the web in the sRGB colour space. sRGB is the standard to which most monitor manufacturers loosely adhere, so it gives your images the best chance of acceptable reproduction. Once again - I can't guarantee that calibration will give perfect results on the world wide web, but I can guarantee that non-calibration will give worse results.
The technical aspects of calibration
Broadly speaking, there are three facets of the calibration/profiling process:
1. Brightness (or "Luminance"). This is a physical adjustment that you make before or during the calibration (and on some monitors, is the only physical adjustment that it's possible to make). Brightness is important - it plays a more significant role in your editing than you might think. Many people have had the experience of receiving prints that were too dark, because their screen was too bright. (Of course, the ambient light in which you work plays a part too.) It's very important to choose a suitable brightness setting.
2. Gamma. This can be thought of as the "midtone brightness" of your screen. This isn't a physical adjustment - it's dealt with in the profile. The standard gamma is 2.2, and there's no need to deviate from that.
3. White temperature. This is the colour of the white of your screen, and can range from warm to cool (yellowish to bluish). This can be either a physical adjustment, or a profile setting, depending on your setup. 6500K is considered the standard white temperature for calibration, but some screens don't respond well to being forced to this setting. For those screens, it's better to leave the white temperature unchanged ("native").
What calibrator should you buy?
I've written some specific recommendations for your purchase here.
Can you calibrate with software only?
NO.
There are various programs which claim to calibrate your monitor, and they're all fraudulent. They all rely on your eye to help, and the human eye is way too feeble for this. Calibration MUST be done with a hardware device.
After calibration - what then?
Ultimately, the proof of the pudding is in the printing, so to speak. After calibration, it's time to compare some prints to the screen. Make sure they're prints from a reputable pro lab, not just any old shopping centre photo kiosk.
Please understand that you don't need new prints after you've calibrated. Prior prints will do, as long as they're from your regular (good) lab, and as long as you didn't allow the lab to do any "auto correction" on your files before printing. A lot of people make the mistake of thinking that they need to get new prints to test a new calibrator. Of course this isn't true - your lab doesn't change the way it prints just because you have calibrated your screen. Any recent prints are fine.
If you haven't done any printing yet, go ahead and take the leap. Some labs let you get test prints done for free, which is great.
When choosing photos as your subjects for screen comparison, make sure you choose at least one black-and-white print (pure black-and-white, not tinted), and a few colour ones encompassing a range of different tones.
While you're waiting for the test prints to arrive, I strongly encourage you to read my article here, which discusses some very important issues surrounding the comparison of prints to screen.