The white point in colour definitions is probably one of the least known parameters on a display’s spec sheet. What does it even mean? White is white, no? Most people know it is the combination of all wavelengths of light. So how come different settings exist in the market? The reason is that the theoretic value of white is never seen in reality.
If you look at a white piece of paper for example, it will be coloured by the light source that shines on it. In other words it will look different when you look at it under sunlight conditions, than under artificial light in your office. The same goes for displays. However, the cool thing is that we can often choose the white point of the display. Tampering with the white point setting will consequently impact and define the mood of the image. Note that for convenience we will be talking about displays in this article, but the same goes for just about any visualisation device, including projectors and direct view LED tiles.
If you have ever looked more closely to display settings, you will probably have noticed that the most commonly used white points are 5000K and 6500K. The ‘K’ stands for ‘Kelvin’, and is indeed the official unit to indicate temperature (with 0 Kelvin being -273.15°C or -459.67°F). So that’s where the term ‘colour temperature’ comes from. But why is the actual temperature unit used for this? Aha, that’s where we come to the interesting part…
A little history
In the late 1800s, scientists discovered that black objects radiate different colours if they are heated to high temperatures. German physicist and Nobel Prize winner Max Planck described a hypothetical ideal black body object that reflects absolutely no light, but radiates different wavelengths of light with increasing temperature. Think of it as looking to a gas burner: the hottest centre spot glows blue, while the outer edge lights up red (with yellow and orange in between). Although this ideal black body object only exists in theory, Planck could still determine the wavelengths of light it would emit at different temperatures (don’t you just love theoretical physics?).
So how does this connect to the settings of your display I hear you say? As said, absolute white is just a theory and never seen in reality. A display works with a light source, which has a slight native hue to it. This native white point is commonly indicated in the display’s specifications. However, advanced software can change this hue, and match it to different temperatures on the Kelvin scale. This is not an absolute match (don’t worry, your display is not as hot as a gas burner), but a measure of the colour hue of white light, corresponding to the colour that would be emitted by a hypothetical black body.
When to change the white point setting?
If you use your screen only for watching movies or for common office work, then you will probably never need to change the white point setting. As said, your eyes will automatically adapt to the setting of your display. The default colour temperature of the sRGB (standard Red Green Blue) colour space, commonly used for computer monitors, corresponds to 6500K by the way.
However, the white point setting is important if you are a professional designer or creator. Then it is best to set the white point as close as possible to the destination of your work. If you are a graphic designer, and your work will be used in print, then 5000K is a good choice. This corresponds best with the common lighting conditions for reading printed materials, and is a yellowish version of white. However, if you are designing for the internet, then 6500K is a better option as displays commonly have a higher white point. Just drive around in the evening and look at the light of the TV screens or computer monitors you see. It is dominantly blue, because this bluish colour setting is the default for computer screens. This is the same for movies made in the USA or Europe. Japanese movies, on the other hand, are shot for 9300K.
Defining the white point
For many displays, you can define the white point (although it is not always called this way). Sometimes you can choose between some standard values (commonly 5000K, 6500K, 7600K and 9300K) or you can select the white point yourself from 5000K to 10000K in steps of 500K. For consumer televisions for example, you can select the colour temperature to be more red or more blue (which is equivalent of selecting the white point). Only professional users, for whom colour is crucial as the display should show the image as it is intended to be seen, calibrate their screens. Also reference monitors used in film production for example, are calibrated.
Where to use it
You can thus define the white point. But in which environments is this really needed? Many users will play around with the setting at first installation, but then leave it in the selected position. However, in some environments an exact white point is crucial. For example, when the display or video wall is used as a broadcast studio backdrop, the white point determines the mood of the complete broadcast. This means a lot of attention is given to this spec. The freely adjustable white point, combined with our renowned colour accuracy, makes Barco’s laser rear-projection video walls and Barco UniSee a preferred visualisation solution for use in television studios.
A special kind of white point selection is used in control rooms, where the colour temperature changes throughout the day. In night mode, the amount of blue colours will be diminished, to prevent eye strain.
Barco’s unique Sense X automatic colour and brightness calibration system, also allows white point adjustments. You can freely select the white point to any colour temperature between 3200K and 11000K. This system is available on Barco’s rear-projection video walls (both LED-lit and LASER-lit) and LCD video walls. This gives you the flexibility to precisely select the mood of the image you want.
Although the white point is not the best known specification for many users, it can sometimes make a huge difference in the display’s performance. Especially in environments where a certain ‘mood’ is to be set with the screen, it is essential to select the best suited white point.