The science behind calibration and the benefits of getting your TV or projector calibrated
If there’s one question that commonly gets asked of a professional calibrator, it’s “why should I get my TV or projector calibrated?”
It’s a fair question and many people might wonder why a TV or projector can’t just be shipped already calibrated by the manufacturer. The main reason is that it would require them to individually calibrate each screen in the factory and this would be both impractical and expensive, adding to the cost of the display. In addition, any calibration in the factory wouldn’t take into account the ultimate viewing environment, nor would it be able to allow for a running-in period. So given these factors it makes far more sense to keep the cost associated with the display as low as possible and allow those that are interested, to employ the services of a professional video calibrator once they have bought their new TV or projector.
The situation is often made worse by manufacturers deliberately shipping displays in picture settings that will attract potential buyers in a shop but are far from ideal at home. Although even when this isn’t the case, no mass-produced consumer product will ever be perfect straight out-of-the-box, so to get the very best from your new TV or projector you will need to hire the services of a professional video calibrator. The analogy that is often used is that of a high-performance sports car - you could simply drive it off the forecourt but to get the very best from from your new purchase there will be additional costs involved. The same is true of any display and, as an AVForums member once pointed out, people budget a certain percentage of the cost of their system for cabling, so why not spend an extra £200-250 getting your TV or projector professionally calibrated?If you want your TV or projector to be as accurate as possible and perform optimally you'll need the services of a professional calibrator.
This is especially true of higher-end TVs and projectors, not only because they tend to have better controls but also because the fee for a professional calibration is a much smaller percentage of their actual cost. If you’ve spent £5,000 on a display you really owe it to yourself to get it professionally calibrated. However, it would be uneconomic to spend £200-250 on a professional calibration if the display in question only cost slightly more than that in the first place. Although just because a display is cheap that doesn’t mean it can’t be calibrated - many manufacturers include extensive calibration controls on even their entry level models. It also doesn’t follow that just because a TV or projector is cheap it won’t benefit from a calibration, it’s simply harder to justify the expense.
Luckily there are some very simple tweaks that you can perform yourself before even considering hiring a calibrator, so even the cheapest TV can get a quick and easy performance boost. As we’ve already mentioned, manufacturers have a tendency to ship TVs in settings that are designed to catch your eye on a shop floor. As a result pictures are often too bright, whites are too blue and colours are exaggerated. With the FIFA World Cup fast approaching, now is the perfect time to get your TV picture more accurate, so the pitches don’t look florescent and the Brazilian players’ shirts don’t look radioactive. All you need to do is simply select the Movie or Cinema picture mode and you will find that you’re already a long way towards achieving a more accurate image on your TV or projector.
Another common issue is that TVs are usually shipped in an aspect ratio that ‘overscans’ - that is zooms into the picture - so that you can’t see the edges. This hides digital junk on the border of some TV broadcasts, thus saving the manufacturer from customer complaints about something that's beyond their control, but it also creates scaling artefacts and robs high definition images of some of their resolution. Again this is easy to correct and when watching high definition content you should always choose the aspect ratio that matches the resolution of your panel with that of the broadcast, thus ensuring you catch all the detail as you watch England’s inevitable early exit in Brazil. Unfortunately each manufacturer uses a different name for this aspect ratio but you can find all the information you need, and much more besides, on our Picture Perfect page.
Following the steps in Picture Perfect will certainly help but these factory-set picture modes are limited in how accurate they can be and that’s why you’ll find yourself considering the next step. If you’re the kind of person that wants their display to perform to the best of its ability and be as accurate as possible, which probably applies to most AVForums members, then what you need is a professional calibration. The primary objective of such a calibration is to ensure that the display conforms as closely as possible to a specific set of industry standards. All the content that we currently watch, be it broadcast TV, DVD or Blu-ray, is created using these industry standards, which primarily relate to the specific colour of white and the other colours in general. A professional calibrator will use the available controls on your display to ensure that it matches these industry standards.Any TV or projector can benefit from a professional calibration but the cheaper the display the harder it is to justify the expense.
By getting your display calibrated you have the peace of mind of knowing that the picture you are watching is exactly what the content creators intended you to see. An example that is often quoted is The Matrix, where the Wachowskis used a very deliberate colour scheme to subtly differentiate between scenes in the real world (blue) and scenes in the Matrix (green). When the film was being transferred to DVD and Blu-ray, the Wachowskis would have been looking at a monitor that had been calibrated to exactly the same industry standards used by every professional calibrator. So if you have your display calibrated, you can guarantee that the image you are watching replicates the creator’s intent as closely as possible. Whilst the primary goal of a calibration is to ensure your display matches these industry standards, there are other benefits to be gained.
The calibrator will also seek to optimise your display’s performance in terms its dynamic range (the difference between black and white), its video processing and the overall brightness of the image. They’ll also turn off all those unnecessary picture features that manufacturers love to add but which rarely have a positive impact on picture quality. In the case of a TV, the calibrator will create both Day and Night settings which are designed to optimise the performance for different viewing environments. You don’t want your TV too bright at night when it’s dark because that can be fatiguing for the eyes but conversely, you might need a brighter image during the day when there’s a lot more ambient light in the room. If your TV or projector supports 3D, the calibrator will also create a calibrated 3D setting using the same industry standards but this time adjusting for the effect of the 3D glasses themselves.
You might be tempted to calibrate your display yourself and whilst you can certainly set some of the controls such as Brightness, Contrast and Sharpness using easy to access test patterns, the more advanced controls require specialised equipment - primarily a colour meter, a test pattern generator and calibration software. For TV and projector reviews here at AVForums we use Klein K-10 and i1 Pro meters, along with Sencore pattern generators and CalMAN calibration software but there are plenty of other meters, generators and software available. The important thing is that any professional calibrator you hire has some combination of these three key pieces of equipment. Anyone turning up at your door without the essential tools and claiming they can calibrate by eye should not be trusted.
You could of course buy these tools yourself but even the cheapest combination would cost considerably more than a professional calibrator will charge and you won’t necessarily know how to use them properly. That requires professional training provided by either the Imaging Science Foundation (ISF) or THX and whichever calibrator you decide to use should be qualified with one or, ideally, both of these organisations. Although it's worth pointing out that the training provided by the ISF and THX is essentially the same because they're both using exactly the same set of industry standards. Ultimately when you hire a professional calibrator what you're paying for, aside from the expensive equipment that can often cost thousands of pounds and the training, is their experience. They will probably be familiar with your particular TV or projector and will know exactly how to ensure it is accurate and performing optimally.You could try calibrating your display yourself but after you factor in the cost of the equipment its easier and cheaper just to hire a professional.
So what exactly does a calibration involve? Well, the same basic process applies whether the calibrator is creating a Day, Night or 3D setting. First of all the calibrator will select the most accurate picture preset and then ensure that all the picture processing features have been turned off. These so-called 'special features' are almost always detrimental to image quality. They will also make sure that any sharpening or edge enhancement features are turned off because again this adversely affects the image quality, especially with high definition content. Then they will measure the colour temperature and choose the setting closest to D65 (6500K), which is the industry standard for the colour of white. After that they will set the Brightness and Contrast controls using test patterns to ensure that the dynamic range (the difference between black and white) of the display is as wide as possible. This ensures that the dark parts are as black as possible with losing shadow detail (crushing the blacks) and the white parts are as bright as possible without also losing detail (clipping the whites).
After this a professional calibrator will measure the Gamma curve which exists in all the content we watch and thus needs to be adjusted for in the TV setup. The higher the gamma number the darker the overall image but for a TV in a normal living room, a gamma of 2.2 would probably be most appropriate. If you have a projector in a dedicated home theatre then the calibrator might use a higher gamma, maybe 2.4 or even 2.6. The reason the calibrator will actually measure the gamma curve is that whilst the display may have a setting of 2.2 that doesn’t mean it will track at that number and, in actual fact, a different setting might be closer. The calibrator will select the most appropriate settings but some displays also offer controls that allow for fine tuning of the gamma curve, which can be useful.
Whilst many of the controls mentioned so far could be set using a basic calibration disc, when it comes to calibrating the Greyscale and Colour Gamut the calibrator will need specialist equipment. The greyscale, as the name suggests, is a scale going from black to white in shades of grey and it’s the most important part of the image. The best way to describe the greyscale is as the canvas on which the image is laid, so if the greyscale isn’t accurate then nothing will be. The idea is for the calibrator to adjust the levels of red, green and blue (the three primary colours) so there are equal amounts resulting in a smooth transition from black to white in shades of grey, with no discolouration. Almost every display has at least a 2-point White Balance control which allows the calibrator to adjust the levels of red, green and blue at two specific points and thus balance out the entire greyscale. Some displays also include a 10-point white balance for a greater level of control. By correctly setting the greyscale the calibrator is also able to precisely adjust the colour temperature of white and fine tune the gamma, as all three are interconnected.
Once the greyscale has been calibrated and assuming the display has a colour management system (CMS), the calibrator can then correct the colours themselves. In general the colour accuracy will have improved after the greyscale has been calibrated, which is why it's done first. There are a number of different types of CMS but the best allow the calibrator to adjust the three primary colours (red, green and blue) and the three secondary colours (cyan, magenta and yellow). They should also allow the calibrator to adjust the three elements of colour - saturation, hue and brightness. The idea is to use these controls to ensure that all six colours are precisely hitting their targets for the industry standard of Rec.709. Since all the controls on a display have a tendency to interact with one another, once the calibrator has finished with the CMS they will check everything again and fine tune where necessary. After that it's just a case of running a report for the customer, making a note of all the settings and, where possible, locking the calibrated modes.Whether you'll notice any difference after a calibration will largely depend on how accurate your display was to start with.The obvious final question is, having got your TV or projector calibrated, will you notice any difference? The honest answer is that it'll largely depend upon how accurate your display was before the calibrator arrived. If you followed all the guidelines on the Picture Perfect page, the difference may not be huge but you will have the comfort of knowing that your display precisely matches the industry standards and thus reflects the creator's original intent. However if your display used the default settings it was shipped in then the difference will be more pronounced; although it’s possible that you might not initially like the calibrated results, perhaps feeling that the image is dimmer, less colourful and the whites appear redder.
As we mentioned earlier, this is because the default settings created by manufacturers are often too bright, too saturated and have too much blue in the whites. After a calibration, the brightness of the display will have been set to maximise the dynamic range of the screen whilst remaining comfortable to look at. The colours will also be more natural, precisely matching the industry standards, as will the colour of white which will initially appear redder because all that excess blue has been removed. It will take time for your brain to adjust but, after a few days looking at your calibrated image, switch back to your previous setting and you will be acutely aware of the improvements.
Whether you feel a professional calibration is worth the cost is largely a matter of personal preference, although the value of your display, the available controls and your budget will also be factors. However, if you do decide to get a calibration, at least you'll know your TV or projector is accurate and perhaps you can finally relax and just enjoy watching it. You might even be free of the video enthusiast's curse - the compulsion to constantly fiddle with the settings. The rest of your family might not understand all the complexities and benefits of a professional calibration but they'll at least be grateful for that!
If you're interested in a professional video calibration, you can find your nearest calibrator here.
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