The quality of light cannot be measured by a single universal parameter as it consists of several factors that have different effects on the human body and perception. For a comprehensive assessment of the quality of the light, the following aspects should be considered:
(1) Spectral power distribution (SPD):
- Describes the intensity of light at each wavelength.
- A balanced spectrum that mimics natural sunlight is ideal.
- It is measured using specialised radio spectrometers.
(2) Light intensity (lux):
- Indicates the amount of light falling on a given area.
- The recommended values vary according to the type of activity and environment.
- It is measured using a luxmeter or a radio spectrometer.
(3) Correlated colour temperature (K):
- Expresses the colour of the light â warm, neutral or cold.
- It affects the atmosphere and perception of space.
- It is measured using a colorimeter or a radio spectrometer.
(4) Colour rendering index (CRI):
- Expresses how faithfully the light reproduces colours compared to natural light.
- The higher the CRI, the truer the colour rendering.
- It is measured using a colorimeter or a radio spectrometer.
(5) Unified glare rating (UGR):
- Expresses the degree of glare caused by the light source.
- Lower UGR means less glare and greater visual comfort.
- It is calculated based on various lighting and environmental parameters.
(6) Flicker effect:
- Flicker effect refers to a rapid fluctuation in light intensity that can cause headaches and eye strain.
- State-of-the-art LED lights should have minimal or no flicker effect.
- It is measured using specialised flicker effect meters.
(7) Circadian efficiency:
- Expresses how light affects the body through circadian rhythms.
- Higher circadian (melanopic) efficiency means greater stimulation of the body during the day and better preparation for sleep in the evening.
- It is measured using specialised circadian efficiency meters â radiospectrometers.
For laymanâs measurements:
If you donât have specialised measuring instruments, you can judge the quality of light subjectively:
- Visual comfort: Do you feel comfortable and not subdued under the light? Does it, or does it not dazzle you?
- Colour rendering: Do the colours look natural and true to life?
- Eye strain: Do you feel eye strain after spending a prolonged period of time under the light?
- Sleep: Do you have problems falling asleep or do you experience issues with the quality of your sleep after being under the light in the evening?
If you have any doubts about the quality of light in your environment, we recommend consulting a lighting expert who will take professional measurements and propose an optimal solution.
