Lux Recommends: Led panels with smart optics

The latest optical technology now means that you can have improved performance and better viewing conditions from other configurations than a uniform, flat panel recessed in the ceiling. 

We reviewed standard LED ceiling panels in December 2017.  This new article considers the alternatives and to understand why, we need some historical background.

For most of us, offices have usually been illuminated with fluorescent tubes. Linear fluorescent lamps, as single or twin and typically 1.2, 1.5 and 1.8m long (4’, 5’, 6’), were used. To reduce glare, they usually also had an extruded plastic diffuser over the bare tube.

With the increasing use of standardised dimensions and modular building techniques, suspended ceilings were frequently used to conceal the wiring and building services, such as heating and ventilation ducts. In these ceilings, the 600 x 600 mm (2’ x 2’) panel, with four linear or compact fluorescent lamps, became almost the way to light an office. Opal or prismatic diffusers hid the lamps from direct view and where there were computer screens, aluminium louvres were used to minimise glare and uncomfortable reflections.

The introduction of energy efficient, high power white LEDs with good colour rendering made fluorescent lighting of offices obsolete in a very short space of time. Even the highly efficient T5/T16 lamp disappeared quicker than most people could possibly have imagined. The square, recessed, LED flat opal panel fixture was seen everywhere.

However, not all panels are the same. Panels which diffuse light of equal intensity in all directions are likely to be glaring and cause reflections on computer screens. Micro-prismatic and panels with light guides give better lighting because they control the angle of the beam – mainly by limiting the light emitted above 65 degrees.

Some of these panels are very good and you can achieve uniform and comfortable lighting and still save a lot of energy compared with a fluorescent scheme. However, the result can be visually uninteresting and you do need to check that the panels meet standards, such as EN 12464, in terms of limiting glare. Always ask to see the glare calculation, UGR, for your particular installation.

The luminaires below are some of the better alternatives to a flat panel.  Note that not all the panels are 600 x 600 mm but most are.

All of them are very good, maybe because of their target market, and there was nothing I could really find wrong with any of them.

 

Concord Pixer by Sylvania

The Pixer is a brand new product and comprises four square individual pods which are about 250 mm square (10”). These are mounted within a rigid frame. In effect, the pods can be arranged as 600 x 600 mm or 300 x 1200mm (2’ x 2’ or 1’ x 4’). The pods can be individually adjusted so that they are flush with the ceiling or dropped down about 30 mm. Having them dropped directs more light on to the ceiling thus giving greater visual comfort and a less contrasting appearance.

When switched on, the vertical sides of the pods glow whilst the much larger horizontal face has a combination of clear polycarbonate layered with a nano-structure optical film to keep the glare rating, UGR, to <19. This polished polycarbonate has a glossy finish which reflects its surroundings and gives the luminaire an upmarket appeal.

The rather complex construction also means that air handling is a standard feature of the luminaire.

There are both high output (132 lm/W) and high efficiency (150 lm/W) versions depending on whether you want maximum illumination or minimum energy consumption.

Tunable white and high colour rendering, CRI> 90, surface mount and direct/indirect versions will be available later this year.

 

 

 

Dextra Rubix

At first glance, this appears to be a simple 9-cell luminaire, with the square cells having semi-specular aluminium reflectors. However, what makes the appearance interesting is that the cells are recessed in to a dished opal diffuser. This diffuser has its own light source which glows thus giving a soft surrounding light to the cells when switched on. It does look very nice.

The diffuser lighting can be switched separately and thus used as low level background lighting or for emergency operation.

The cells have an effective cut-off of 65 degrees so they meet the <19 UGR criteria for almost all installations.

A nice extra touch is that there is the option of clip-on coloured surrounds for the cells. They are available in red, blue, orange etc and a neat way of adding a bit of colour to the ceiling. You could also use them to identify separate areas of a large open plan office.

 

 

Etap U3

This is an interesting panel in that, depending on the number of rows of LEDs fitted, the output can be from 2,000 lumens to 7,000 lumens. In effect, each row of LEDs emits about 1,000 lumens. We looked at the 4,000K version which delivers 3,500 lm from three rows.

The main face of the panel is a textured white polymer and the LEDs are set deeply behind clear, square lenses. Each recessed row of LEDs additionally has moulded crossways shielding units and these are available with a white or aluminium finish.

As you would expect, these shielding units control the luminous intensity at various angles. Two variations are available. The very wide angle version limits the UGR to <19 and the medium angle limits the UGR to <16.

The Etap U3 also has one of the best data sheets I have seen in terms of information about intensity, photometric data and Utilisation Factors.

 

 

iGuzzini Laser Blade XS

Strictly speaking, this isn’t a ceiling panel; it is much smaller. However, it can be square, has clever optics and could achieve a similar light output and distribution. It is also available in linear versions.

The basis of the Laser Blade family is the miniaturisation of the optics. The 18 mm (0.7”) diameter reflector has hundreds of accurately shaped facets. This reflector, sometimes with a lens, is then mounted in a square or linear frame.

The sample we looked at has a 3 x 3 array of reflectors. This measures approximately 65 mm (2.5”) square and emits 860 lm. You could easily make an arrangement of four of them to give you a similar output to a regular ceiling panel but less than half the size.

There is a variety of light distributions, typically from 24 – 55 degrees.

 

 

XAL Unico Q9

The Unico is a family of luminaires made from individual cells which are approximately 40 mm square (1.5”). A cell is typically 4W and all have a CRI >90. The cells can be grouped in lines or squares.
The Q9, unsurprisingly, has nine cells, 3 x 3. Typically, this arrangement would emit 3,000 lumens from a luminaire which is 120 mm x 120 mm (5” x 5”).

There are six different optical distributions and what is especially interesting is that you can have different optics in the individual cells. For example, you might want six cells for wallwashing and the other three as a narrow angle downlight. Apart from a narrow spot lens, all the other beam distributions are achieved with finely engineered micro-facetted metallised reflectors.  The beams range from 12 – 75 degrees and there is also a wallwasher option.

The Unico certainly allows for a different approach to lighting design and gives much more flexibility.

 

 

 

Zumtobel Mirel evolution

This is unusual in that it has six by six array of cells; many more than the other panels reviewed here. Each cell is 62 mm (2.5”) square and is made of the same white polymer material as the front face. Inset in each cell is an LED module with a finely engineered, precision, prismatic lens.

There are two light distributions available. The standard version limits the luminance to <1,500 cd/m2 at 65 degrees. This produces a glare rating, UGR, of <16 in all viewing directions.
There is also a Wide Beam version which version limits the luminance to < 3,000 cd/m2 at 65 degrees. This produces a glare rating, UGR, of <19 in all viewing directions.

Another reason to use this product is that, in my experience, their technical data and support is second to none.

 

 

  • See the latest lighting systems at LuxLive 2018 at ExCeL London on Wednesday 14 November and Thursday 15 November 2018. Entry is free if you pre-register HERE.