BASIC TERMINOLOGY
Luminous flux (lm)
Luminous flux or luminous power simply specifies how much light the source emits. The unit of luminous flux is lumen (lm). According to this specification, a suitable replacement for a conventional incandescent light bulb is determined (although it is only a comparative value because a light emitting angle is also important).
| Conventional incandescent bulb (W) | 15 | 25 | 40 | 60 | 75 | 100 | 150 |
| LED – Luminous flux (lm) | 136 | 249 | 470 | 806 | 1055 | 1521 | 2452 |
Colour Rendering Index CRI (Ra)
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The colour rendering index tells you how faithfully the light source shows the colours. Maximum (and ideal) value is 100, however, the CRI around 80 is considered to be good enough, and LED sources with high-quality chips have no problem to reach this value. |
Colour Temperature (K)
The colour temperature or the light colour is given in Kelvin and specifies the colour spectrum to which the emitted light belongs. Broadly speaking, it is about how “warm” the light appears to us, and there is a simple proportion – the more kelvins, the cooler light. The warm white colour of light that corresponds to about 3000 K is typical for conventional incandescent bulbs and is more suitable for areas intended for relaxation. For work and activities that strain the eyes (e.g. reading), it is better to use the neutral white colour (about 4000 K) and cold white colour (from 5000 K).
