Colour temperature
This parameter describes the general coloration of the light of the lamp in "warm" or "cold" tones.
Initially, colour temperature is the temperature (in kelvins) of an object at which it begins to glow in a certain colour. Interestingly, the higher its value, the more “cold” the colour is: for example, the dull red glow of a heated metal corresponds to 800-1000 K, and the bluish-white tint of a fluorescent lamp corresponds to about 6000 K.
The temperatures encountered in modern light bulbs can be described approximately as follows:
2700 – 3000 K — "warm" white light, similar to traditional incandescent lamps;
3000 – 3500 K — "slightly warmer than average";
3500 – 6000 K — neutral white, similar to daylight;
More than 6000 K — cold shades of white.
Note that the colour temperature is not directly related to the quality of colour reproduction provided by the light of a particular lamp — much depends on the features of its design and, accordingly, the spectral colour balance.
Scattering angle
The angle of light dispersion is the space in front of the light bulb, which is illuminated by the source itself, and not by the light reflected from the walls and interior items. In other words, the angle of light scattering determines the zone of the best illumination. Classic incandescent bulbs demonstrate the widest dispersion angle — they shine almost 360˚. LED spotlights have the smallest illumination angle, which are able to illuminate well only the area directly under the bulb — the scattering angle in such cases is about 15˚. Of course, a large angle of light scattering is not always needed. Working in the evening at the table, you need light only in front of you, so as not to disturb anyone. For spotlights that light up only small objects in front of them (a painting, sculpture, bas-relief, etc.), the scattering angle can even be from 4 °. As for the top (general) lighting, in this case it is better to choose something with a wider dispersion angle. These bulbs provide extremely uniform illumination.
Claimed running time
The service life of the light source claimed by the manufacturer is implied, during which the illuminator is able to generate the claimed brightness and temperature colour spectrum. It is believed that light-emitting diode (LED) bulbs have the longest service life — their working life can be 10,000 — 50,000 hours (
50 years of operation), depending on the modification of the bulb. But this parameter cannot be regarded as a guarantee, since
a lamp with an operating time of 25 years can work less, and maybe even more, than
a lamp with a "life" of 30 or even
35 years. In second place are energy-saving fluorescent light bulbs that are capable of generating daylight — the service life of such is in the range of 2000 — 20,000 hours. The average service life of halogen bulbs is about 2000 — 4000 hours, but when the power supply is equipped with a soft start device, it can be almost doubled. In last place are classic incandescent bulbs, the service life of which is within 1000 hours.
