The Brighter Choice
This term is applied to a white-light source such as an LED lamp, module or luminaire. A tuneable white-light source is one in which the corelated colour temperature (CCT) of the light generated can be dynamically adjusted.
CCT is measured in kelvin (K) and applies to white light only. In simple terms, CCT describes if a white light is warm (with a distinct yellow hue), neutral or cool (with a slightly blue hue). For more details , please check the article What is correlated colour temperature (CCT) ?
Most white-light sources (such as a commercially available LED lamp, LED strip, or a light fitting) have a fixed CCT. This is usually in the range of approximately 2700K to 6500K. The lower values (c2700K -c3500K) have a higher % of the red and yellow (longer) wavelengths and are often called “warm” white – because that is the feeling they stimulate in most people.
In the middle of the range (c 3500K – 4500K) the light is described as neutral white and is comprised of a balance of longer and shorter wavelengths.
At the upper end (c4500 – c6500K) the light has a higher % of the blue (shorter) wavelengths and is usually described as “cool” white.
A tuneable white-light source is one which can produce white light with different CCT values in response to a suitable control signal. A true tuneable fitting will be able to generate any CCT value within a range – it is not restricted to a small number of pre-set values.
Most tuneable white fittings are designed to be controlled with a DALI-2 control system.
The tuneable white-light fittings or LED strips used in a tuneable white installation will each contain two arrays of LEDs – a warm-white array and a cool-white array.
The driver in each fitting (or controlling each section of strip) will control both arrays separately from each other, so that the warm-white array and the cool-white array can be brightened and dimmed independently of each other. This is possible by using what is called a device type 8 (or DT8) driver. These drivers support the latest version of DALI (DALI-2) that contains CCT specific commands and allows one address (the driver) to have two output channels.
When the appropriate DALI-2 commands are sent to the driver by the control system the driver regulates the relative output of the two channels (warm and cool) so that the desired CCT is achieved, AND it regulates the overall output so that the required light level is achieved.
DALI-2 based control systems are the most widely used method to implement a tuneable-white light installation. Other control methods that could be used include DMX control systems, but they are much more commonly used with RGB (or colour changing) lighting installations – see below.
Tuneable white-light fittings will almost always be used in a circadian lighting installation, generating white light with a CCT that gradually changes (rather than altering in abrupt steps) throughout the day. For more details on circadian lighting, please read the article Human Centric v Circadian Lighting
RGB tuneable lighting is more commonly referred to as “RGB”, “colour changing” or “RGB colour changing” lighting.
These terms are applied to a light source comprised of separate red, green and blue LEDs in which these different colours are mixed in varying proportions to create a wide range of colours.
RGB or colour changing lighting is widely used in entertainment and decorative lighting to create a wide range of changing colours. For example, this technique can be used on the façade of a building or on a feature wall in a bar, club or restaurant. The purpose of the technique is usually to create an effect rather than to provide functional lighting for a task.
RGB colour changing lighting is rarely static. It is usually used to create a constantly changing pattern of different colours. To do this, a control system is required and DMX is the most widely used control protocol for this application.
Tuneable white light is concerned with small and subtle changes in the hue of white light. A tuneable white fitting will only ever produce white light, but the quality of the white light generated will vary between “warm” and “cool” white.
RGB tuneable (or colour changing) lighting is concerned with generating a very wide range of different colours, often in a dramatic fashion and quite quickly.
Tuneable white light v RGB colour changing light - summary
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Tuneable white |
RGB colour changing |
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Colour range controlled |
Narrow – hues of white only |
Very wide – almost any colour of the rainbow |
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Speed of change |
Usually slow & gradual |
Sometimes fast and dramatic |
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Preferred control system |
DALI-2 |
DMX |
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Purpose |
Functional lighting – to enhance well-being and to support our circadian rhythm |
To create a mood, dramatic effect, for entertainment or to project a brand image |
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Typical applications |
Indoors, in classrooms and offices |
Outdoors on building facades; indoors in clubs, bars and restaurants |
DMX is preferred for colour changing applications because of the large number of individual channels and addresses on a single system, and the high rates of data transmission that are possible.
DALI-2 is preferred for tuneable white applications because tuneable white is usually needed alongside other lighting control functions such as presence detection and light level control (so integration with sensors is required) and end-user override. These functions require two-way control, and DALI provides this (at the expense of high data rates) whereas DMX does not.
