{"id":1088,"date":"2019-10-17T08:41:18","date_gmt":"2019-10-17T08:41:18","guid":{"rendered":"http:\/\/dijkstra.com\/?page_id=1088"},"modified":"2020-01-28T13:02:12","modified_gmt":"2020-01-28T13:02:12","slug":"over-licht-en-armaturen","status":"publish","type":"page","link":"https:\/\/www.dijkstralampen.nl\/en\/over-licht-en-armaturen\/","title":{"rendered":"Light and Fixtures"},"content":{"rendered":"
\n\t\t\t\t\t\t
\n\t\t\t\t\t\t\t
<\/div>\n\t\t\t\t\t\t
\n\t\t\t\n\t\n\t\n\t\n\t\n<\/svg>\t\t<\/div>\n\t\t\t\t\t
\n\t\t\t\t\t
\n\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t\t\t\t\t\t\t\t\t\"\"\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t\t\t\t\t\t\t\t\t\"\"\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t\t\t

About light<\/span><\/h1>

One of the first questions that should be posed when planning a lighting installation is: \u2018What are the primary functions of the lighting?\u2019 The answer to this question will depend on the sort of space that needs lighting, and the sort of job that needs to be done in said space. In rooms or areas where visual tasks have to be carried out, the so-called \u2018workspaces\u2019, the primary function of the lighting is of course to improve the visual prestation.<\/span><\/p>

Lighting in corridors inside buildings must be sufficiently safe so that even in darkness, safety is guaranteed. In places meant for social contact however, visual prestation is not a priority and the emphasis is almost completely on visual comfort. Other functions of light include medical functions or the beautification of an area.<\/span><\/p>

Fixture efficiency<\/span><\/h1>
The fixture efficiency is the quotient of the luminous flux emitted from the fixture and the flux emitted from the accessory lightsource(s). The energy efficiency of a lamp is quotient of the emitted rays of light and the power that is used to fuel these.<\/div>

Luminous flux F<\/span><\/h1>

All radiation energy emitted by a lightsource that is perceived by a human eye is the luminous flux F. Simply put, the luminous flux is the measure for the amount of visible radiation (=light) a lightsource emits. The unit that is used is lumen (lm).<\/p>

Evenness<\/span><\/h1>

The evenness is the ratio between the minimal and average illuminance on a surface.<\/span><\/p>

Colour temperature<\/span><\/h1>

Materials emit light, the colour of this light is dependent on the temperature. Every given temperature has an accesory colour: the colour temperature. The colour temperature is measured with degrees Kelvin (K). This matches the colour of the light that a metal alloy will emit at certain temperatures. It is a way to precisely measure different kinds of colours and their shades.<\/p>

White lightsources can be divided into three categories based on the colour of the light.<\/span><\/p>
Colour temperature<\/span><\/td>Colour of the light<\/span><\/td><\/tr>
< 3300 K<\/span><\/td>Warm (red-like white)<\/span><\/td><\/tr>
\u00a03300 – 5300 K<\/span><\/td>Medium (white)<\/span><\/td><\/tr>
> 5300 K<\/span><\/td>Cool (blue-like white)<\/span><\/td><\/tr>
\u00a02000 – 2500 K<\/span><\/td>Yellow-white<\/span><\/td><\/tr>
\u00a02500 – 2900 K<\/span><\/td>Extra warm white<\/span><\/td><\/tr>
\u00a02900 – 3300 K<\/span><\/td>Warm white<\/span><\/td><\/tr>
\u00a03300 – 5000 K<\/span><\/td>Neutral white<\/span><\/td><\/tr>
> 5000 K<\/span><\/td>Cool white<\/span><\/td><\/tr><\/tbody><\/table>

To make sure that light is of good quality, the colour temperature of the light should be relative to the level of illuminance. Experience has learned us that it is better to use a higher colour temperature for higher levels of illuminance. So, the higher the level of illuminance, the \u2018whiter\u2019 the colour of the lightsources should be.<\/span><\/p>

Colour rendering<\/span><\/h1>

Colour rendering has to do with the amount of lightfrequencies that are present in the visible spectrum of light. When all frequencies are present, colour rendering is 100 per cent. All colours are clearly visible when this is the case. Once frequencies are missing, colours are perceived in a dinimished fashion. This is expressed in a coefficient: the colour rendering index (CRI).<\/span><\/p>

\"\"<\/span><\/p>

As a rule, artificial light should give the human eye the possibility to correctly see colours, just like regular daylight. This of course depends on both the place and the function of the light. The CRI measures the similarity between the colour of an object (as perceived by the eye) and that of a light source. To calculate the CRI-values, eight test colours are defined and subsequently lit using the light source. The degree in which the colours differ from what they are when lit using the light source determines the CRI values. A lightsource with a CRI value of 100 shows all colours exactly as they are. In case of a low CRI value, colours are not visible correctly.<\/span><\/p>

Luminance L\u00a0<\/span><\/h1>

The luminance L of a lightsource or a lit surface expresses the degree of brightness perceived by the eye. The corresponding unit of measurement is candela per square meter.<\/span><\/p>

Luminance<\/span><\/h1>

Luminance is a concept that is mainly used to characterize relations between different degrees of brightness in indoor areas. A room that is lit very monotonously, meaning that different parts of the room are lit to more or less the same extent, is often experienced as dull and unstimilating by people that work there. In museums however, an equal distribution of luminance is preferable to focus the attention on the objects on display. When brightness contrasts are too great in a visual environment, the eye needs to constantly adjust to these contrasts. This can lead to exhaustion and, especially in work environments, to a loss of productivity. For this reason a rule of thumb for lighting work environments is that the luminance-ratio between the visual job, the direct environment of the visual job and the further environment should be approximately 10:3:1.<\/span><\/p>

Illuminance E<\/span><\/h1>

Unit of measurement: lux [lx]. The illuminance is the luminance per surface. A luminance of 1 lux arises when a luminance of 1 lm is equally distributed over a surface of one square meter.<\/span><\/p>

Diminishing light output<\/span><\/h1>

The moment a system of lighting has been made operational, the average light output of this system will eventuall diminish over time. This diminishment is caused by:<\/span><\/p>