The quality of television images depends on many aspects, and the accuracy of color reproduction in television images is one of these important factors. In order to obtain accurate color reproduction of TV images, it is necessary to understand the impact of good lighting sources, lighting fixtures, cameras, and other factors on it. This article focuses on a simple discussion from several aspects such as light sources, lighting fixtures, and lighting distribution.

1、 High quality light source

1. Natural light source

The color temperature and color rendering of the light source are the most important parameters that affect the color reproduction of television images. Color temperature and color rendering are determined by the spectral composition of the light source. The spectrum of sunlight is evenly distributed from long to short waves, and the distribution of spectral energy is continuous. The color rendering index CRI is defined as 100, making it the most ideal light source. If the light source contains a large amount of red, the color temperature of the light source will be lower and tend to be reddish; If the light source contains a large amount of blue light, the color temperature of the light source is higher and tends to be blue.

Sunlight is an ideal light source. In the production process of television programs, it is often involved in using outdoor shooting or directly recording outdoors. Generally, sunlight is the most direct light source to meet the shooting needs. In the standard requirements for television lighting systems in China, it is stipulated that the color rendering index of the light source that meets the requirements for color restoration of television images is above 85. In addition, the variability of the color temperature of sunlight allows us to choose the appropriate shooting time according to our needs, and shoot TV images with better color reproduction. In short, sunlight is a very high-quality light source for color reproduction in television images, and it can be said that the sun is the best light source for color rendering.

2. Artificial light source

The device or device that converts electrical energy into light energy is called an electric light source. The main electrical light sources used for recording programs include halogen tungsten lamps, short arc xenon lamps, metal halide lamps, three primary fluorescent lamps, and semiconductor light sources (LEDs). With the continuous development of electric light sources, LED electric light sources are currently mainly used in television shooting.

LED light source is an emerging mainstream lighting source with the characteristics of energy conservation, environmental protection, high light efficiency, and pure light color. The spectral energy distribution of LED light sources is discontinuous, especially the white light generated by RGB mixing, which does not have a full spectrum like the sun. In this way, it is not appropriate to use the color rendering index CRI to evaluate some LED light sources. That is to say, some have low color rendering index but good restoration effect. In order to find a good representation method, several representation methods such as color quality index (CQS) and television light source consistency parameter (TLCI) emerged later. Overall, they are closer and more perfect to the characteristics of LEDs. LED light source lamps are adjustable in color temperature through certain technical means. In order to find a good representation method, several representation methods such as color quality index (CQS) and TV light source consistency parameter (TLCI) have emerged. Overall, they are becoming closer to the characteristics of LED and more perfect. LED light fixtures are adjustable in color temperature through certain technical means, which is particularly convenient for television production.

Color gamut and color restoration

2、 Suitable lighting fixtures

If you want to do good work, you must first sharpen your tools. With a good light source, it is necessary to have suitable objects to apply it, and the lamp is the one that achieves this function. In news studios or some small and medium-sized studios, spotlight and soft light are mainly used.

A spotlight is a lamp that can produce a spotlight effect, usually a point light source. Determine the color temperature based on the type of light source selected. Traditional halogen spotlights have low color temperatures, while current LED spotlights have adjustable color temperatures, ranging from high to low. Soft light with soft lighting mainly produces astigmatism, and the color temperature varies depending on the light source. Dispersion is a common problem in spotlights in the past, which can cause inconsistency in color temperature and color rendering index between the center and edge of the spot. This is because when light passes through the lens, the refractive index of each monochromatic light is different, and the edge monochromatic light just shines on the host's face, causing skin color "spots" or uneven skin color. A properly designed lighting fixture can effectively solve the dispersion problem. The threaded spotlight can control the size of the spot through effective control technology, accurately locate it, and achieve both spotlight and astigmatism effects. Soft astigmatic light is essential for TV lighting. Once the light is too hard, the host's face will be overexposed or the foundation make-up after makeup will be displayed. After the color restoration of the screen, the face looks abnormal. Soft light can avoid this problem very well in many cases, which is also one of the reasons for the daily use of soft light.

The astigmatic surface of soft light lamps is relatively large, making it difficult to control the direction, so different angles of grilles are usually needed to control the direction of light output. Once there is too much stray light, it not only makes the picture appear cluttered but also seriously affects the color restoration of the TV picture. If there is too much stray light on the large screen, it will make the screen gray, making it difficult to restore the correct colors of the content placed inside the screen; Stray light flying onto some scenes can also lead to a decrease in the color saturation of the scene's self illumination or rendering with lighting fixtures, resulting in poor color reproduction of the TV screen. Spotlights are relatively more effective in controlling the direction of light, so during daily dimming, appropriate lighting fixtures will be selected based on the actual situation on site to ensure normal color restoration of the TV screen.

3、 Excellent Lighting Engineer

One of the key factors affecting the accuracy of color reproduction in television programs is the application of lighting equipment and the control of television images by lighting engineers during the production process. Excellent lighting engineers will determine the selection and application of lighting fixtures based on the actual situation on site, determine the appropriate lighting illuminance, control the light ratio, understand factors such as cameras and makeup, and take into account various factors that affect the color reproduction of the on-site TV screen.

4、 Accurate TV camera

In the process of television program production, basic work such as stage costumes and lighting are essential, all prepared to capture good television images. The medium for achieving the transformation from real scenes to television images is the television camera. Accurate television cameras play a crucial role in obtaining normal color reproduction of television images, so it is necessary to understand the use of television cameras.

5、 Powerful post color correction

There is a crucial link between recording and broadcasting in television programs, which is post production. In addition to editing videos and creating special effects, color correction is also an important task in post production. In the early stage of TV program recording, no matter how well we do our work, there may be color deviation in the picture. Once color deviation occurs, it is necessary to achieve color balance in the picture through color correction in the later stage, so as to achieve a normal color restoration of the TV picture.

In the process of television program production, in order to obtain a normal color reproduction of the television picture, lighting designers should learn to unify and reasonably apply these influencing factors such as television light sources, cameras, and post production. Reasonably using TV light sources that meet recording requirements, understanding the working principle of the camera, and assisting in post production technology will make it relatively easy to achieve color restoration of TV images.