Light meters, light meters. Light is part of the spectrum of electromagnetic radiation from the range of wavelengths visible to the naked eye. Sometimes visible light is also called electromagnetic radiation of any wavelength (for example, ultraviolet rays, which cannot be seen by the naked eye, and which cause the fluorescence of various materials, are often called black light). Humans and animals have different biological makeup of the eye, so not everyone can see a certain color equally. That is why, in addition to the physical unit watt (Watt), the physiological unit lumen (lm) is used for light intensity. So if there is some light intensity, e.g. 1 lumen, then a person has the same feeling of visibility, regardless of the color of that light. But in a physical sense, it is not the same for us if some light has a power of 1 watt, because we have the feeling that it is a light of one watt if the green color is much stronger than red or blue.
