How times change. When I last wrote about this topic, there were just six manufacturers of luminaires where you could remotely alter the correlated colour temperature, or CCT, of the light source. Nowadays, almost every manufacturer has a tuneable white option in its range.
Typically, a tunable white luminaire for commercial use can vary the appearance from a warm 2700K to a cool 6500K. In this review, we have excluded those mainly residential luminaires that mimic incandescent lamps by operating at 3000K at full output and then reduce down to maybe 2000K, becoming warmer the more you dim them. They are often called dim-to-warm lamps.
Of course, the big question is why would you want to alter the colour appearance? The original purpose of tuneable white luminaires was dynamic lighting where you change the appearance of the space throughout the morning, afternoon and evening.
A work area or entrance hall could be bright and airy with a cool appearance during the morning and then a softer warmer appearance late afternoon and towards the evening.
The appearance indoors could also follow that of the daylight outside. In this way, you have a more natural-looking light which changes with the passing of time.
More recently, there has been a huge upsurge of interest in the effect of lighting on health and the body’s circadian rhythms – its sleep-wake cycle.
The topic has various names including biodynamic lighting and human centric lighting, HCL. One of the well-established manufacturers in this field calls it Visual Timing Light, VTL.
As well as commercial applications, the healthcare sector is a major user of tuneable white luminaires.
Care homes, for instance, can introduce warm light in the late evening to make the atmosphere more conducive to sleep. Equally, patients in hospital wards can also adjust their lighting to suit their mood.
The crucial element for these applications is the control system. You need to be able to vary both the colour temperature, CCT, and the illumination level but what illumination level do you want and for how long?
What should the CCT be, should it change at the same time as the illumination and at what periods during the day? What about after dark?
There is a huge amount of research literature (and hype) on this topic but one of the best independent, and simple to read, summaries is the position statement on circadian lighting which is obtainable free from the UK’s Society of Light and Lighting.
One final point about control systems is that you need to check which one will be used with your tuneable white luminaire. For example, Dali 6 requires two addresses per luminaire whereas Dali 8 requires just one.
The simplest way to achieve a tuneable effect is to use two LED modules; one warm (say 2700K), the other cool (maybe 6000K).
Intermediate CCTs are obtained by combining and dimming the two modules. Of course, this also alters the light output and hence the illumination level.
This has the advantage of simplicity. Another benefit is that the source retains its high efficacy in terms of lm/W.
The disadvantage is that the intermediate whites can look a bit odd because the colour will stray away from the black body locus.
The reason is that you have a straight line (between the two warm and cool LEDs) trying to match the black-body curve.
The bigger the difference between the warm and cool CCT, the worse it becomes. Even that isn’t straightforward because LEDs with identical CCTs may have different spectral compositions.
The solution is to conduct a trial before embarking on a full installation.
Ideally, to maintain a good appearance across the range of CCTs and a high colour rendering index (CRI) when dimmed, the luminaire needs to have additional coloured LEDs.
For example, one solution is to combine RGB plus amber plus a white to achieve the correct balance throughout the dimming range. These are termed RGBAW modules.
The disadvantage of multi-chip systems is that you can lose efficacy. One reputable manufacturer quotes a delivered 45lm/W for its tuneable white system.
Other than healthcare and HCL systems, retail is another sector using tuneable white LEDs.
Instead of stepping outside (and risk being collared as a shoplifter!) to see what an item looks like in daylight, you simply flick a switch on the wall of a changing room to alter the colour temperature.
Similarly, you can see what the evening appearance of a garment would look like under a dimmed tungsten lamp or candle light.
AOne Smart FR | Aurora
The basis of this IP65, 6.5W fire-rated luminaire is the company’s well-known mPRO downlight. To this, Aurora has added a ‘Smart Inside’ driver which enables a variety of control via the AOne app. This has a whole host of features. The tunable white option can alter the colour from 2200K to 5000K. The AOne app is also programmable so that, for example, you can set the downlight to come on at a certain time of day with a particular colour temperature. You can also programme different scenes both through the day and the seasons of the year. The AOne app can be used together with Smart Things, Amazon’s Alexa or the Google Assistant. A light output of 640 lm means that the target market for this downlight is residential rather than commercial.
Pleiad 165 | Fagerhult
This particular die-cast aluminium, 165 mm diameter model from the Pleiad rate is 25W with a typical output of 2,100 lm for the fixed CCT versions. The colour temperature varies from 2700K to 6500K. Fagerhult says that one of the benefits of its tunable white is its high efficiency. This varies from 97 lm/W at 2700K to 124 lm/W at 6500K. The cooler the light, the more efficient is the luminaire. CRI is maintained above 90 across the whole range and peaks at 95. The red R9 metric varies from 52 to a peak of 77.
D70 | Glamox Luxonic
Glamox merged with the long-established Hampshire-based Luxonic Lighting on 6 April this year. Currently, we understand that both brand names will continue to exist. The D70 is a range of quality, die-cast aluminium downlights in four different sizes from approximately 105 to 210 mm in bezel diameter. The output of the tuneable white versions is typically from 1,100 to 3,200 lm and there are four reflector distributions, so they are very suitable for office and light industrial interiors. Interestingly, Glamox Luxonic offers two versions of tuneable white. One uses just two LEDs of 2700K and 6500K. The other uses a mixture of red, green and blue LEDs. This gives a greater range from 2500K to 7000K. Glamox Luxonic claims a CRI >90 for both options.
But something to watch out for when reading the technical literature is that the company sometimes uses CCT to mean Colour Change Technology!
Prescolite LF6ML | Hubbell
Hubbell Lighting encompasses several brands, one of which is Prescolite. This one-piece, sheet steel 33W recessed unit delivers over 3,000 lumens. The aluminium reflector is available with six different surface finishes. The tuneable white is offered in two versions: 2700K to 5000K and 2700K to 6500K. Standard dimming is achieved with 0 – 10V but colour temperature control is via its SpectraSync colour tuning technology. This can also be used for what Hubbell calls Scheduled White. In effect, this is a simple scene-setting application. This is connected to its NX Distributed Intelligence control system which links luminaires, occupancy sensors, photocells and wall switches.
ProSpex MiniTRIM | Lucent
A lot of specifiers turn to Lucent because of its wide range of downlights. This 15W, 86 mm diameter recessed downlight has a bezel of less than 5mm wide. The colour temperature ranges from a very warm 2000K to a cool 5000K. The colour rendering at 3000K is >90 Ra. What I particularly like about the ProSpex is the comprehensive data sheet which shows colour rendering under various metrics such as TM30 gamut and fidelity as well as the circular colour vector graphic. Lucent even quotes a correction factor for the light output at various colour temperatures.
LuxSpace | Philips Lighting
Philips Lighting was one of the earliest companies to take circadian rhythms and human centric lighting seriously. As such, the tuneable white luminaires it offers have a huge range of expertise behind them. For commercial and healthcare applications, Philips offers the LuxSpace range of downlights and the PowerBalance range of recessed ceiling panels. The big difference is that there are two standard tuneable white programmes. One mimics natural daylight in that the light output from the luminaire is warm at the beginning and end of the day. In the middle of the day, the CCT and light output increases. The other programme is called ‘Bio-rhythm Support’. This boosts the CCT and light output during the morning until around lunchtime. These both change during the afternoon achieving the warmest CCT and lowest output at the end of the day.
Junistar ISOSafe | SG Lighting
SG Lighting is the new name for Riegens which is a well-established name amongst designers and specifiers. It has a huge range of downlights but I chose this one because the 8.5W Junistar ISOSafe does so much. Firstly, SG Lighting says you can mount it directly in insulation. You can also tilt it at 30 degrees from straight down. It is IP44 and using the company’s LEDDim technology, you can alter both lighting level and colour without extra cabling. It has a colour rendering of CRI >90 and a claimed rated life of 100,000 hours (L80/B50). The standard colour range is 2700K to 6500K but SG Lighting also offers 2000K to 4000K for domestic applications. The latter is similar to dim-to-warm lamps but has independent control of light level and colour temperature.
Elan | Tamlite
Downlights aren’t always the best way to light a space and a linear luminaire may be a better choice. The Elan can be surface mounted or suspended and is fitted with a semi-opal micro-prismatic diffuser. The body is extruded aluminium. The standard luminaire is 4000K but the tuneable white version ranges from 3000K to 6500K. Both have a CRI >80. Control of the dimming and colour temperature is via Tamlite’s Vision Connect system. This is a simple to use programmable and scene set system which uses Dali and Bluetooth.
Lavigo | Waldmann
If you are seriously interested in circadian rhythms and how light affects humans, then there is a lot of very good information on the Waldmann website. The company has been interested in this aspect for years. For these applications, Waldmann strongly recommend direct/indirect systems such as free-standing luminaires or those suspended from the ceiling. As an example, the Lavigo direct/indirect luminaire has a built-in control system and programme based on your geographical latitude. The factory-set programme then alters the CCT, timing and light output accordingly. The colour changing works on the indirect component so you get the greatest effect from the large area of the ceiling. This scheduling can only be over-ridden by a Waldmann programmer. The Lavigo also has integral occupancy and daylight harvesting sensors which makes it more efficient without compromising the human centric factors.
Panos Infinity | Zumtobel
This IP44, 23W, 1,700 lm unit has recently been upgraded. The main difference comes from the use of an amplitude modulation dimming system instead of the previous pulse-width modulation-based one. The new system means it can now fade smoothly to zero; the previous cut off at 15 per cent. It is also much more efficient in terms of delivered lm/W. Due to some really clever software from Tridonic, the Panos Infinity can be controlled for both dimming and CCT by using just one Dali 8 address. You can achieve constant light output and, therefore illumination level, across the complete range of CCTs. The colour range is 2700K to 6500K and with a CRI >90. Both the smooth and facetted reflectors have a zero-iridescence finish. Medium to large installations can be controlled via a Dali system but for smaller applications, Zumtobel has a simple BasicDim wireless control.