In the early days of T5 fluorescent tubes it was apparent that high levels of light require new reflector solutions to maximise the efficiency of the light source, while reducing glare. T5 offered an increased luminance from 14,000 cd/m² to 17,000 cd/m². With LED, this has rise to 300,000 cd/m². LEDs produce an intense light which can be harsh on the eye unless managed correctly. And what is the point of saving money on lighting if no one can stand to be in that room? Fagerhult’s innovative glare-reduction technology circumnavigates these issues, taking full advantage of the efficiency whilst ensuring user comfort.

Visual experience

Unique solutions for comfort

The great challenge with LEDs is to keep glare within reasonable levels. It is not unusual that diodes and LED modules have a luminance (light intensity) of over 300,000 cd/m². In contrast, a standard T5 fluorescent tube has a luminance of 17,000 cd/m². Light from an LED or LED module has to be controlled by reflectors, lenses, or some other form of diffusing material. All Fagerhult LED luminaires have been specifically developed to offer optimal visual comfort. For instance, our new Pleiad G3 downlight range is equipped with a unique shielding system AGC (Advanced Glare Control) to achieve this result.

Color Temperature

The colour temperature of a LED is expressed in Kelvin. The colour temperature of an LED may vary from one manufacturer to another even if they report the same measurement. In addition, the colour temperature of an LED can change over time, which means that the value after several thousand hours of use will not be the same as that for a new product. Equally the luminaire plays a significant role as driving it too hard or insufficient cooling can both have a negative influence.

The accuracy of the colour quality of an LED luminaire is is defined in MacAdam ellipses in Standard Deviation of Colour Matching (SDCM) on a scale of 0-10. Between 0 and 4 is it difficult to see differences in colour, but further up the scale it can have an obvious and negative disparities. The requirements for most other Indoor environments are usually around MacAdam 3–5 SDCM. By comparison, a T5 fluorescent tube from a major manufacturer is about MacAdam 4.

White light

Blue and yellow becomes white

Usually white light is created by applying a phosphor based coating to a blue diode, either directly on the diode or on a separate plate over it. This coating converts some of the blue light to white light of various colour temperatures – in a process similar to a fluorescent tube. The quality of the light is determined both by the specification of the blue LED and by how carefully the phosphor is matched to the selected diode.

Colour Rendering

Colour re-production

Colour rendition in LEDs is not exactly the same as in traditional light sources, but it is still described as Ra/CRI. The Ra scale is from 0 to 100 and measures the capacity of the light source to render colours. Dependant on selection, the Ra of an LED varies between 60 and 95. A high Ra often produces a somewhat lower luminance.

Normally, colour rendition is measured using the CIE method on a scale of eight colours. The Colour Rendering Index (CRI) is given as an average value (Ra), so it is possible for a light source to be good at rendering seven colours but not as good at the eighth. A complementary scale is called CRI 1–14, which contains six more colours