1.Luminous Flux

The amount of light emitted by the LED light source per unit time is called the luminous flux of the LED light source.

Unit: Lumen, i.e. lm. The amount of light emitted by a light source per unit time is called the luminous flux of the light source. Again, this amount is for the light source, is the size of the total amount of light emitted by the light source, and is equivalent to the optical power. The greater the luminous flux of the light source, the more light is emitted.

For the isotropic light (i.e. the light of the source is emitted at the same density in all directions), then F = 4πI. That is, if the I of the light source is 1 cd, the total luminous flux is 4π = 12.56 lm. Compared with the mechanical unit, the luminous flux is equivalent to the force, and the luminous intensity is equivalent to the pressure. If the spot to be illuminated needs to look brighter, we must not only increase the luminous flux, but also increase the means of convergence. In fact, it is to reduce the area so that we can get more intensity.

2.CRI(Color Rendering Index)

It refers to the color rendering index. The color rendering ability of a light source to an object is called color rendering, and is compared with the color of the object under the same color temperature reference or reference light source. The spectral content emitted by the light determines the color of the light source, but the same light color can be made up of many, a few or even only two monochromatic light waves, and the color rendering of each color is also very different. Light sources of the same color have different spectral compositions, and light sources with a wider spectral composition are more likely to provide better color rendering quality. When the source spectrum has little or no main wave reflected by the object under the reference source, the color produces a significant color shift. The greater the degree of chromatic aberration, the worse the color rendering of the color by the light source. The color rendering index coefficient (Kaufman) is still a common method for defining the color rendering of light sources.

3.Color Temperature

It is expressed by the absolute temperature K, which is a standard black body heating. When the temperature rises to a certain extent, the color begins to change gradually from deep red-light red-orange-white-blue. When a light source and the black body have the same color, the black body is then the absolute temperature of the light source.

Since the correlated color temperature is actually the black body radiation approaching the light source color, the evaluation value of the light source color performance is not an accurate color contrast, so the two light sources with the same color temperature value may still be some differences in the light color appearance. Color temperature alone is not enough to understand the color rendering ability of the light source to the object, or how the color of the object is reproduced under the light source.

The color temperature of the light source is different,and the light color is different.

When the color temperature is below 3300K, the light color is reddish to produce a steady atmosphere and a warm feeling;

When the color temperature is between 3000K and 6000K, there is no obvious visual psychological effect in this color tone, and it produces a refreshing feeling, so it is called "neutral" color temperature.

When the color temperature is over 6000K, and the light color is blue, offering people a feeling of coldness.

a. Color temperature and brightness: Under the illumination of high color temperature light source, if the brightness is not high, it will give people a kind of dark atmosphere. While if under low color temperature light source, the brightness will be too high, which will give people a feeling of sultry heat.

b. Comparison of light color: If two kinds of light sources with large color difference are used in the same space, the contrast will have a layer effect. While if the light color contrast is large, the layer effect of light color can be obtained at the same time obtaining the brightness level.
       Irradiation with a low color temperature light source, it makes the red color vivid;
       Irradiation with a medium color temperature light source, it makes the blue color fresh;
       Irradiation with a high color temperature light source, it makes the object cold feeling.

4.Wave Length

It is the distance between two consecutively identical points at the same time in the direction of the periodic wave propagation. Light and radiation are electromagnetic radiation (The energy travels from one object to another, without any medium in the process of transmit. This type of energy transmit is called radiation) into the human eyes, which can be converted into light by the optic nerve., that is the part of the spectrum seen by the naked eyes. These rays have a wave length range between 360 and 830 nm and are only a very small part of the electromagnetic radiation spectrum.