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Technical analysis
Luminous Flux and Efficiency represent the key information for the evaluation of the performance of a product. What do they represent exactly? Luminous flux represents the emission of the LED source, that is the total amount of light produced by the light source.
Efficiency represents the ration between the emission and the power absorbed by the source, that is the total amount of emitted light divided per the energy consumed by the LED source. Nowadays there is not a sole way of publishing these data, each company on the market makes its own choice. This means that catalogues of different companies publish different kinds of information, ranging from the data declared by LED producers to values referable to the LED source in peculiar conditions, but also to values that take into account the “loss” due to reflectors, lenses, drivers and so onIn general, the most reliable data is the value measured on the fixtue in its effective usage conditions. In order to let our customers have a clearer idea of the declared data, Duralamp specifies for each LED fixte both its effective flux/efficiencvalues and the values directly referable to the source, as declared by the producer. The purpose of this methodic choice is to simplify the understanding of the data, and, consequently, to provide our customer the immediate possibility of comparison among Duralamp lighting fixtues and those by other brands. The rapid technical progress of LED sources results in continuous changes in terms of luminous flux and, consequently, efficacy. The information provided by the catalogue should therefore be referred to the date of publication - for regularly updated information please visit the site web.
LED lamps, unlike traditional lamps do not suddenly stop working but gradually decrease their initial flow unless there are defects or electric shocks. A LED lamp is considered to be no longer functioning it reaches 70% of their initial flow (L70). Life tests are performed following standard IES LM-80.
The life span of LED lamps is strongly influenced by the lamps operating temperature once they are installed in fixtures. Duralamp fixtures are designed to have a very low LED operating temperature to ensure the lamps have a very long lifespan. According to the IEC / PAS 62717 standard, the useful life of a LED can be defined with an additional parameter, for example 50'000h L80B10, meaning the period of time (50'000h) in which 10% (B10) of the LED products of the same type has gradually fallen below 80% of the initial nominal flux.
The working temperature of a LED source has a significant effect on its useful life, maintenance of luminous flux and efficiency. Correct temperature management, i.e. thermal management of the power in use is a crucial factor in ensuring the performance and reliability of products.
The main characteristic to determine reliability of a product and consistency of performance is measuring the junction temperature (Tj), that can be measured indirectly as luminous flux and the useful life are linked to this parameter. Tj values between 60°C and 90°C allow you to have products with high reliability, performance and estimated lifespans that adhere to market demands.
Careful attention must be paid when reading the declared data given that LED manufacturers provide data on the flux at a temperature of Tj 25°C, a condition that is not physically possible for normal use where the LED source is turned on and tested in a fraction of a second and does not produce any heat. Duralamp products are measured and characterised for thermal stability to provide real data on everyday use for the catalogue and users. Well-designed fixtures that ensure proper dissipation also ensure constant flow, colour and spectrum parameters as well as reliability and durability in the declared lifespan.
UGR (Unified Glare Rating) is a unified factor in the international field developed by the CIE (International Commission on Illumination) to evaluate direct discomfort glare due to the use of lighting products. In the European Standard relating to indoor workplaces UNI EN 12464-1, the UGR varies from a minimum value of 10 (no glare) to a maximum value of 30 (considerable glare). The lower the value the lower the glare. The UGR value needs to be calculated because it takes into account the size and characteristics of the environment, the background luminance (ceiling, wall, etc), the luminance of light fixtures and the position of the latter in relation to the observation point.
UGR - classification - applications
<13 - imperceptible
≤16 - perceptible - technical drawings
≤19 - perceptible - reading, writing, schools, offices, working on a pc
≤22 - perceptible - industry and crafts
≤25 - uncomfortable - raw industrial jobs
≤28 - uncomfortable - railway tracks, warehouses
>28 - intolerable
LED lamps have extensive production tolerances in relation to chromaticity. For years Duralamp has only used lamps with colour consistency that is measured using the MacAdam Ellipse system. This allows for absolute repeatability of the colour characteristics compared to the binning based system. LED lamps used by Duralamp are at least 3-steps of MacAdam (3SDCM).
The colour rendering index CRI indicates the ability of a light source to reveal colours faithfully. Lighting a coloured object with two sources with different CRI will reveal different colours depending on the source used. It is important not to confuse the CRI with data relating to the colour temperature of a source (expressed in K); two sources with the same colour temperature can have different colour rendering indexes. The CRI strongly influences the efficiency of a LED source and many times lighting designers have to choose between the quality and quantity of light. The LED sources that are fitted in products in the Duralamp collection normally have a colour rendering index that reaches CRI 85. In some case there are also sources with a high colour rendering index (CRI>95).
The Colour Rendering Index Ra or CRI, is a dimensionless index that ranges from 0 to 100 and partially describes the capacity of a light source to faithfully render the colour of a consistently lit object in line with what a reference source would do. It is based on the adherence of a source to the light emitted by a tungsten filament evaluated on a panel of 14 colour samples, of which only the first 8 are taken into consideration, none with saturated hues.

The TM-30 index allows for a more complete reading on the way a source is able to render colour. It introduces the concept of saturation, uses a balanced mixture of incandescent lamps and sunlight as a reference and extends colour samples to 99 subdivided into 7 reference areas with colours from nature for example flowers and leaves, skin tones, colours of paintings, textiles, plastics, printed material and 14 CRI colour samples.
The additional information that TM30 can give is provided by two graphs that summarise the values relating to Rf, Rg and Hue Shift (a shift in the colour hue, or the perception of a false colour compared to what we would see in sunlight), and the second how the source works for groups of materials (99CES) for immediate understanding:

The “rendering” of the source is expressed with a series of explanatory graphics of the colorimetric and qualitative characteristics and 2 distinct indexes.

The fidelity index Rf, which describes the ability of the source to render colours.
It varies on a scale of 0 to 100 where 100 is perfect adherence. It is also possible to have Rf targeted on one of the seven reference areas. For example “Rf skin” refers to the ability of the source to express the colours relating to the reference area concerning skin tone. It is similar to Ra but can be lower given that the reference colours range from 14 to 99.


The Gamut index Rg, which expresses the saturation level of the colours lit by the source. It varies on a scale from 60 to 140.
Values lower than 100 indicate a decrease in saturation, higher values indicate an increase in saturation therefore more vivid colours.

Colours will be more or less saturated depending on whether they are inside or outside the reference circle.
The last in-depth graph is the detail of the deviation and rendering of semitones compared to the reference source that is represented by the following diagram:
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