About the light
General information or what to look for when selecting light source
Proper lighting is a key factor, crucial during the autumn-winter season, where we have to utilize artificial light for most of the day.
In order to ensure best working conditions a few factors need to be considered:
- Proper colour temperature - white light 4000-5800 Kelvin.
- High CRI (Color Rendering Index) which means the faithfulness of colour reproduction and should be above 90 Ra.
- Proper brightness expressed in lux or lumen.
- Uniform lighting of the whole workspace and minimization of shadows (impossible to achieve with spot lighting).
- Ability to regulate the height and angle of the light.
Colour is determined using the so-called colour temperature (Tc) and is given in Kelvin [K]. White light, which is considered optimal, as it does not falsify colours is between 5000 and 5800 Kelvin. Colours above that are cold, below - warm.
Colour Rendering Index (CRI)
CRI and Ra are units used to denote just how well the colours of illuminated objects are presented. The higher the index the better the colour reproduction,
and the more natural-looking the objects appear. The best light we have is sunlight, with a virtually continuous spectrum: from the violet all the way to the red, where all the composite colours are strongly emitted. The Ra of the Sun is 100.
In all works, where the colour is of high importance, the lamps used should be characterized by Ra of at least 90-100. Our ability to perceive colours comes from individual colours that constitute white light. In order see colours clearly we need light that is rich in all colours. If the light source lacks a given colour spectrum, or has weak emission of a given colour, certain items will be characterized by falsified colour.
To summarize, the higher the CRI (or Ra) the better the colour reproduction.
Proper amount of light
The minimum required light intensity for office work is 500-750 lux according to PN-IN norms (http://archiwum.ciop.pl/11583). In comparison, sunlight on a cloudy day is about 80 000 lux. Therefore, in order to increase comfort and work efficiency, the light intensity should be as high as possible. We should also remember about the surface on which a given number of luxes is achieved, which will ensure uniform lighting of the workspace. In case of spot lighting it is impossible.