Camera low light concept

行业内人士强调，照度能低到多少，不仅要看镜头的光圈大小（F 值），更要看是在什麽条件限制下才能出现所标示的LUX 值，否则只是流于数字的游戏罢了！以光圈大小（ F 值）而言，光圈愈大则其所代表的F 值愈小，所需的照度愈低。另外电子灵敏度（ELECTRONIC、SENSITIVITY）是否提高，单一画面累积帧数为多少？红外线是ON 还是OFF？……等都应了解清楚，才不致被规格所标示的照度数值所混淆。

The evolution of low-light cameras in the Chinese market

1. The evolution of low-light cameras in the Chinese market can be simply divided into the following three steps: color during the day/black and white at night (COLOR/MONO) conversion;
2. Slow shutter speed (SLOW/SHUTTER)
3. Ultra-sensitive camera (EXVIEW/HAD).

1. Color during the day/black and white at night (day and night camera COLOR/MONO)

This type of camera still has its specific demand group in the market. In the domestic market, Dijia launched the DIS888C low-light night vision camera in the United States. In the past, night vision cameras of this type have always been the mainstream night vision products.

The lowest illumination value of day and night (COLOR/MONO) cameras in the domestic market is even 0LUX. We can't help but ask: "Cameras are made of optical principles. How can they form images under 0 illumination?"

Color/MONO cameras use the characteristics of black and white images being more sensitive to infrared rays. Under certain light source conditions, they use line switching to convert images from color to black and white so as to match infrared rays. In the process of color/black and white line conversion technology evolution, early companies like PHILIPS, IKEGAMI, and JVC used two sensors (one color and one black and white) to share a set of circuits for switching. Currently, such cameras have adopted a single CCD (color) design. They are color cameras during the day or when there is sufficient light. When night falls or the light source is insufficient (usually 1LUX to 3LUX), the color signal is eliminated by digital circuits to become black and white images. In order to match infrared rays, the infrared filter that is indispensable for color cameras is also removed. Although this method can achieve the purpose of "low illumination" at night, it has the disadvantages of blurred images and unnatural colors during the day, and the camera's shooting distance is limited by the infrared light irradiation distance. According to the manufacturer, in order to make up for this shortcoming, Japan's SANYO once launched a model that uses a motor to control the opening and closing of the filter (that is, the filter opens and closes with the switching of color/black and white images), but this model seems to have disappeared from the market. However, whether the COLOR MONO camera is a "low-light" camera is still quite controversial. Experts point out that the real "low-light camera" should refer to the functions that the camera itself (the components and technology used) can achieve. The color camera during the day/black and white camera at night is limited by the CCD sensitivity and cannot be changed by itself. It only uses line switching and infrared light to enhance the function. It cannot be considered a low-light camera.

2. SLOW/SHUTTER

This type of camera is also called a cumulative camera. It uses computer memory technology to continuously accumulate several blurry images due to insufficient light to form a clear image. The SLOW SHUTTER technology is used to reduce the camera illumination to 0.008LUX/F1.2 (×128), and the number of frames that can be accumulated (128 frames) is at the leading level even among imported brands. This type of low-light camera is suitable for museums that prohibit red and ultraviolet damage, night biological activity observation, night military coastline monitoring, etc., and is used for monitoring in relatively static places. Cameras using SLOW SHUTTER technology are real low-light cameras; some people believe that standard low-light cameras should refer to cumulative cameras.
Currently, this type of low-light camera is dominated by imported brands, most of which are expensive and have a small number of accumulated frames (32 frames).

3. Super Sensitivity Camera (EXVIEW/HAD)

The super-sensitive camera (EXVIEW/HAD), also known as the 24-hour camera, was the most popular model in the world in 1998. Its color illumination can reach 0.05LUX, and black and white can reach 0.003-0.001LUX (it can also be matched with infrared to reach 0LUX). It can not only clearly identify images, but also provide real-time continuous images.
This type of camera mainly uses the EXVIEW/HAD/CCD (super-sensitive CCD) launched by the Sony component factory. It uses patented technology to increase the aperture rate of each pixel of the CCD, thereby achieving the requirement of lower illumination. Since the manufacturing cost of this CCD is still high, the technical threshold for finished product manufacturers to develop this type of camera is relatively high.
EXVIEW HAD CCD+image accumulation technology, and basically eliminates the phenomenon of ghosting, it is estimated that it is also at the leading level in terms of current global technology. Professionals believe that if EXVIEW/HAD/CCD becomes popular, this type of camera will be the most promising surveillance camera.