Shulou(Shulou.com)11/24 Report--

Photo source: pixabay fireworks blooming all over the sky, we always want to use mobile phones to keep this beautiful moment. But looking at the faint fireworks on the phone screen and looking up at the sky, we can't help but wonder: is this the same scene as what I saw? Why do fireworks always seem to be washed off on the mobile phone screen and look so bleak?

Every time we buy a new "body organ"-- a mobile phone, looking at the dazzling configuration, we always struggle for a long time. Most people will pay attention to several important parameters, such as processor, battery life, screen quality, etc., among which the most intuitive parameter of screen quality is resolution. Unfortunately, even if you buy a mobile phone with the most advanced screen technology and the highest resolution, it won't give you the most real fireworks.

At night, the fireworks are lit and exploded quickly against a dark background, showing us a bright and gorgeous visual feast. However, for the mobile phone screen, the perfect display of complex colors of fireworks is the most difficult challenge.

The presentation of color before we understand this challenge, we need to know: how is color perceived and presented? The perception of color essentially depends on the light reflected, emitted or transmitted by the object. When cone cell cells in the retina receive different wavelengths of light, they transmit signals to the brain, which in turn recognizes different colors. The random combination of red, green and blue light can bring out other colors, so it is called optical tricolor (for example, the superposition of red light and green light is yellow light).

Lightness can describe the light and shade of a color, which is related to the doping ratio of white. If we set the luminance value of black to 0 and the luminance value of white to 10, then the brightness of all colors is between 0 and 10. The more white is mixed into the same color, the higher the brightness is and the lighter the color looks. Interestingly, if an object has a higher brightness (luminance, luminous flux per unit area, in nits, nit), its color will also look lighter.

It seems that both brightness and brightness affect the depth of the color. But lightness is an attribute of color, and brightness reflects the intensity of light or reflection on the surface of an object perceived by the human eye. Brightness is not only related to light intensity, but also to the sensitivity of human eyes to different wavelengths of light. For example, with the same intensity of green light and blue light, we instinctively think that green light is brighter. When the brightness is too high or too low, you can't even see the color of the object.

Most objects in nature show different colors by reflecting light, while artificial electronic screens must actively emit light to the human eye. As long as the electronic screen has trichromatic light-emitting devices and can adjust the proportion of trichromatic doping, it can show different colors.

But in fact, the mobile phone screen from the early LCD (Liquid Crystal Display, liquid crystal display) technology to the latest OLED (Organic Light-Emitting Diode) technology, is still limited by hardware, can not show all colors, such as high-purity green and red.

Human eyes are very sensitive to the light and shade changes of light. They can not only detect the subtle dynamic changes of color, but also perceive a large dynamic range of color. Therefore, in order to improve the visual experience, both mobile phones and TV screens are promoting the development of HDR (High Dynamic Range, high dynamic range) technology-- a wider range of brightness, a larger amount of color information and closer to reality. But even so, these screens cannot fully restore the color and brightness of the real world.

Most mobile phone screens display colors in the form of RGB (red,green,blue). The picture shows the microstructure of the OLED screen: red, green and blue pixels. Photo Source: Matthew Rollings's hardest challenge comes back to fireworks, which are similar to electronic screens in that they actively emit light to the human eye. But the color principle of fireworks is essentially a flame reaction-when metal atoms are heated, electrons absorb energy and then release it with specific wavelengths of light. This way of color development determines that the spectrum of fireworks is mainly composed of emission lines-the energy of light is concentrated in a very narrow wavelength range. When different metals and metal compounds are burned, the flame will show different colors. For example, the flame of sodium metal is yellow, while the flame of barium is yellow-green.

From left to right is the flame color reaction of lithium chloride, strontium chloride, calcium chloride, sodium chloride, barium chloride, trimethyl borate, copper chloride, cesium chloride and potassium chloride. Photo source: Hegelrast in order to make fireworks colorful, fireworks usually add chromogenic agents, that is, metal salts, such as strontium salts and lithium salts that appear red, calcium salts that appear orange, copper compounds that appear blue, and magnesium powder that appears silver. By fireworks designers, the metal salt under high temperature will change the color of fireworks flame with temperature and time. But the electronic screen displays colors in RGB tricolor, so it is doomed that it cannot show all monochromatic light (light with fixed wavelength / light that cannot be dispersed).

The display screen presents colors through the RGB color model (the picture shows sRGB) and is doomed to be unable to present some monochromatic colors. Image source: the moment the Dicklyon fireworks explode in the air, the color may change from extremely hot white, to yellow, and then to orange (if magnesium powder is added, there will be silver sparks scattered); the brightness will change from the dazzling light of the explosion to the dimness of the dissipation. Against the dark background of the night, these great changes are yellow from light to dark on the electronic screen, with all the details and levels lost. The gap between fireworks and reality on the mobile phone screen is probably like the gap between fireworks salute and fairy stick fireworks with your naked eyes. Because of the changes in color and brightness when fireworks bloom, fine and wide span, its complexity has far exceeded the display ability of the current electronic screen. So it is not difficult to understand that dazzling fireworks will certainly be greatly discounted on the mobile phone screen.

The comparison between fireworks and fairy sticks. Photo Source: capture of Pixabay screen in fact, without considering the limitations of color output on the electronic screen, it is still difficult to display fireworks perfectly. Because the premise of outputting the real picture requires the perfect cooperation of the input-camera equipment. When you shoot with a mobile phone or camera, the color and shading range that the device can capture determines the quality of the image. The more complete the information about the highlights and shadows in photos and videos, the richer the details and levels of the work will be. The ability of camera equipment to capture the range of picture brightness from the darkest to the brightest, also known as dynamic range, is an important parameter of the image sensor.

Image sensors vary greatly among different devices, and the dynamic range of professional cameras may be twice as large as that of ordinary mobile phones. So you'll find that sometimes it doesn't look good to take a selfie on your phone: when you focus on your face, the background is pale, but if you focus on your back, you can see the background and your face is a mess. This means that you are shooting with your back facing the light source. The mobile phone image sensor is small, resulting in a small dynamic range, so it is difficult to use the mobile phone to capture high-quality images with strong light and shade contrast.

The photo taken against the light: the background is clear and the subject information is missing (but this photo is a silhouette of the subject). Photo source: Pixabay professional cameras have high image quality, but people tend to use more portable phones when they see the golden sunset on the horizon on the way to work. Although mobile phone photos may be subtly different from what you actually see, recording life is enough.

The fireworks in the night are beautiful and shocking, but they are a nightmare for mobile phone shooting and screen display. Next time, let go of the mobile phone and enjoy the fireworks event with our reliable eyes.

Reference link:

Https://www.wired.com/story/the-colorful-science-of-why-fireworks-look-bad-on-tv/

This article comes from the official account of Wechat: global Science (ID:huanqiukexue), written by Wang Yu.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.