Today's mobile phones are basically equipped with LED fill lights for shooting fill lights at night and in dark environments, but the effect of this fill light is not very good. There will always be the problem of whitening, skin color, and object color completely deviating from the normal color. Full spectrum fill lights will come into use at this time.

Let's first understand the full spectrum lamp source:

"Full spectrum lamps, also known as UV-B lamps, can emit the nearest natural light, because the light they emit is full spectrum, that is, all light waves have. It includes visible light of all colors, and a small part of ultraviolet light. Full spectrum bulbs manufactured by various manufacturers include: Duro Test's Vita Lite, Mira 50, Philip's Colortone 50, and Sylvania's Designer 5000K. All of the above bulbs can emit light, which is the most similar to natural sunlight with current chemical technology. These lamps can emit light close to equatorial noon, and their color temperature is about 5000K. Duro Test sells Vita Lite 75 lamp tubes, Strange Company produces Chroma 75 lamp tubes, and Philip produces Colortone 75 lamp tubes. There is a considerable gap between the price and popularity of these lamps. "—— The above is excerpted from Baidu Encyclopedia.

The spectrum is a pattern of monochromatic light separated by a dispersion system (such as prism and grating) after the polychromatic light is separated by a dispersion system, which is arranged in order according to the wavelength (or frequency). It is called optical spectrum in full. In light, the largest part of the visible spectrum is the visible part of the electromagnetic spectrum. The electromagnetic radiation within this wavelength range is called visible light. The spectrum does not contain all the colors that human brain vision can distinguish, such as brown and pink.

We know that both sunlight and incandescent lamps radiate continuous spectrum, which includes red, orange, yellow, green, cyan, blue, purple and other colors within the wavelength range of visible light (380nm-760nm). The object shows its true color under the irradiation of sunlight and incandescent lamp, but when the object is illuminated by the gas discharge lamp with discontinuous spectrum, the color will have varying degrees of distortion. We call the color rendering of the light source the degree to which the light source presents the true color of the object.

In order to evaluate the color rendering of light source quantitatively, the concept of color rendering index is introduced. The standard light source shall prevail, and its color rendering index shall be set as 100. The color rendering index of other light sources shall be lower than 100. The color rendering index is represented by Ra. The higher the Ra value, the better the color rendering of the light source.

(The picture is taken from the Internet) Let's take a look at the picture first. We can see that Figure 1 is the standard light source we mentioned above, and the Ra value is 100. While the true color tube in Figure 2 emits a continuous spectrum, the Ra value is 95, and Figure 3 is the spectrum of the three primary color fluorescent lamp. We can see that there are many colors in the spectrum that are not displayed, and the Ra value is much worse than that of the true color fluorescent lamp. In such a light source environment, the impact on the color of the shooting is quite significant. We can see the sample on the left of the above figure. When the Ra value is equal to 75, the color deviates from the real color seriously, and the overall color turns blue. The color restoration of the sample taken under the illumination of the light source with Ra value of 95 on the right is much more accurate. The higher the Ra value, the closer the light source spectrum is to the full spectrum, and the more light waves and visible light colors the light source contains.

So we can understand that the full spectrum LED fill light will reach a high Ra value, which contains all light waves and all colors of visible light, and a small part of ultraviolet light. It can emit a light that is closest to the natural light source to restore the most realistic and natural color of the subject. The color temperature of natural light we often say is 5500K, but the color temperature of standard light source defined internationally is 5000K, so we can roughly speculate that the color temperature of full-color LED fill light will be between 5000 and 5500K. Today, the official microblog of vivo also revealed that its next flagship model, Xshot, will use a front full spectrum LED fill light as the fill light for self taking. So can the full spectrum fill light on Xshot also be the closest to the effect of natural light? Let's wait for time to verify this.

Speaking of the influence of the color temperature of the fill light on the color of the subject, the latest model of the international mobile phone giant Apple: the iPhone 5S also made efforts in the fill light. At that time, they did not have the concept of full spectrum fill light, but used the design of dual flash lights: a cold color fill light plus a warm color fill light. This cold and warm fill light can automatically set different color temperatures according to your shooting environment. Officials claim that more than 1000 unique combinations can be used to determine the appropriate percentage and intensity of white light and yellow light required. Finally, a more vivid and realistic image is presented. The color tone is neither too cold nor too warm. The highlight effect is more excellent, making the skin color more natural.

From these two solutions, the dual color temperature fill light of Apple's iPhone 5S may be more practical. After all, you can intelligently use multiple color temperature combination fill light according to your current ambient light, which will be more effective. Of course, the effect of full spectrum LED fill light is not bad. At that time, Apple had a dual color temperature fill light, which was designed to restore the true color as well as possible when taking a selfie and turning on the fill light. The full spectrum LED fill light emits the light source closest to the natural light. It is believed that the fill light effect will be greatly improved compared with the previous ordinary LED fill light. However, the iPhone 5S does not have a front fill light (the back of the Xshot also uses the dual color temperature fill light design of the iPhone 5S), and the front full spectrum fill light of the Xshot can control the light intensity according to the ambient light of the current selfie, which may also bring a better selfie experience. In this regard, we have to wait for the real machine to get to know.