During the shooting of pictures and in the scenes where the surveillance system is used, glare is a relatively common but profound problem. It can lead to loss of image details, color deviation, and even complete loss of functionality in night surveillance situations, resulting in inefficiency. Whether you are a person who specializes in photography or a security engineering technician, you need to know effective methods to suppress or eliminate phenomena and situations such as reflection in front of the lens and overexposure. Next, we will proceed based on actual application scenarios, and the system will explain to you several technical solutions to blocking glare that are both practical and extremely efficient.
Why does the camera produce glare?
The main cause of camera glare is that strong light sources directly enter the lens and form multiple reflections between the lens groups. These reflected lights are superimposed on the sensor, causing local overexposure or halo phenomena. Especially in backlight environments, when the sun or light directly enters the screen, the image quality will be drastically reduced.
Modern lenses often use multi-layer coating technology to reduce internal reflections, but cheap cameras often lack coating technology. In addition, the degree of lens cleanliness will also have an impact on glare intensity, and fingerprints or dust will become new diffraction sources, thereby aggravating the formation of light spots. In security surveillance, the root cause of glare problems is often improper installation angle.
How to choose an anti-glare lens
When choosing a lens, the first thing you need to pay attention to is the quality of the coating. Multi-layer nano-coating, also known as MC/ARC, can effectively suppress reflections. Professional-level lenses will generally clearly indicate the type of coating in the specification sheet. However, consumer-level products rarely disclose this information. In addition, the number of aperture blades in the lens structure will also affect the glare performance. The more blades, the more natural the shape of the spot will be.
When selecting a surveillance camera, you should choose a model with automatic aperture adjustment function, which can dynamically adjust the amount of light input according to the ambient light. In a strong light environment, you should choose a model with a built-in ND filter, or add an additional polarizer. For fixed-installation surveillance sites, you can consider using a periscope lens to avoid direct light sources.
How mounting angle affects glare
The camera installation angle is directly determined by the relative position of the light source and the lens. Ideally, the angle between the lens axis and the main light source direction should be kept above 30 degrees. When monitoring outdoors, avoid facing the sunrise/sunset direction of the camera, and avoid reflective surfaces such as glass and metal plates.
In practice, the "clock positioning method" can be used. Assume that the lens is the center of the dial and the strong light source is at the 10 o'clock or 2 o'clock direction. For road monitoring, it is appropriate to use oblique installation methods instead of directly facing the direction of the traffic flow. This can effectively prevent the headlights from being directly illuminated. When installing indoors, be sure to ensure that the camera is not positioned accurately facing the window or lighting fixtures.
The role of polarizers in reducing glare
Polarizer, also known as CPL, works by filtering light in a specific direction. It is an optical accessory. With this filtering characteristic, it can effectively eliminate reflected light from non-metallic surfaces such as water and glass. In photography applications, when you rotate the polarizer ring in a specific direction, you can observe in real time the effect of light and shadow caused by the elimination of reflections achieved through its special operation.
When it comes to security cameras, the options available are thread-mounted circular polarizers or square insert filters. In the field of traffic monitoring, polarized lenses can penetrate the car window glass and clearly capture the images inside the car. When monitoring in waters, it can reduce the impact of water surface waves on images. It should be noted that the polarizer will lose 1-2 stops of light input, and supplementary light measures are required when using it at night.
How software algorithms eliminate glare
Software-based glare removal solutions include modern image processing technology, the HDR algorithm based on deep learning, which can process the bright areas of the image separately, and also process the dark areas of the image separately, and then fuse them. This method has been widely used on smartphones and has also begun to become popular in the security field.
Professional surveillance systems are generally equipped with a local exposure equalization algorithm. This algorithm can identify overexposed areas in the picture and then make local adjustments. Some high-end models also have a spot recognition function. This function uses image restoration technology to reconstruct details obscured by glare. These algorithm processing are usually implemented in real time in the ISP chip, which consumes a relatively large amount of system resources.
The impact of environmental modification on glare control
There are important means to prevent glare. In addition to the optimization of the equipment itself, environmental modification also belongs to this means. Installing a hood for outdoor cameras is the most cost-effective measure. Customized hoods can block stray light incident from the side. Indoors, lighting conditions can be improved by adjusting the light position or by installing blackout curtains.
At the monitoring point facing the light source, you can consider installing a neutral density gradient filter in front of the lens. The upper part of this filter is high-density and can darken the sky. The lower part is transparent and does not affect the performance of ground scenes. In terms of cleaning the glass protective cover, regular use of anti-static cleaner can reduce dust adsorption.
In actual applications, which combination plan do you usually use to solve the glare problem in specific situations? You are welcome to share your practical experience in the comment area. If you find this article helpful, please like it to support it and share it with more colleagues in need. We provide global procurement services for weak current intelligent products!
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