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When lens selection for video surveillance applications is not given enough attention, or is not fully understood, costly mistakes can occur. While understanding the most important considerations in lens selection ultimately leads to success in the system, a lack of knowledge will lead to failure.
The detail in an image is determined by resolution. The shorter the lens focal length, the wider the field of view. Greater than about 90° most lenses start to show curved, barrel distorted images that compress the image at the edges. Rectilinear lenses such as those using Theia Technologies' Linear Optical Technology® don't exhibit barrel distortion and thus maintain image resolution out to the edge of the image.
Those cameras considered true day/night can physically switch the IR filter out of the light path allowing the camera to see both naturally occurring and artificially created IR light. These cameras require day/night lenses to keep the scene in focus both day and night. Day/night lenses are generally more expensive because of the added complexity of focusing a broader color spectrum (from visible through IR) onto the sensor.
Today’s megapixel cameras have many advantages as long as you have the right lens for the job. When that includes covering large areas or reducing cost by installing fewer cameras, that lens is a wide angle lens. Until recently only fisheye lenses were available for an ultra wide field of view. Fisheye lenses create a curved and distorted image which no one seems to like. This significant distortion causes loss of resolution at the image edges.
In the past year a new rectilinear lens giving a different ultra wide view without the barrel distortion or loss of edge resolution of fisheye lenses has been developed. This report is an overview of wide angle lens technology and how we overcome fisheye distortion using Linear Optical Technology®.
“I want a lens that can cover the whole parking lot and I want to be able to read a license plate.” Sound familiar? As a manufacturer of wide angle lenses, Theia Technologies is frequently asked if we have a product that allows the user to do both of these things simultaneously. And the answer is ‘it depends’. It depends on several variables - the resolution you start with from the camera, how far away the subject is from the lens, and the field of view of the lens. But keeping the first two variables constant, the impact of the lens field of view becomes clear. One of the important factors to consider when designing video surveillance installations is the trade-off between lens field of view and image resolution.
It's an exciting time in the security department. You've finally received approval to migrate from your installed analog cameras to new megapixel models and expectations are high. As you get together with your integrator, you start selecting the cameras you plan to install, looking forward to getting higher quality, higher resolution images and, in many cases, covering the same amount of ground with one camera that, otherwise, would have taken several analog models. You're covering the basics of those megapixel cameras, including the housing and mounting hardware. What about the lens?
HD and megapixel cameras have many advantages as long as you have the right lens for the job. When that includes covering large areas or reducing cost by installing fewer cameras, that lens is a wide-angle lens. Wide-angle lenses are not a panacea, but there are many applications that benefit from their use. For applications requiring large areas of coverage, an ultra wide-angle lens on a megapixel camera is a cost-saving opportunity that should be considered. Wide-angle lenses can reduce the number of cameras required to cover an area, reducing cost of installation, maintenance and monitoring. They can be used in place of a PTZ camera when post-incident digital PTZ is desired and effectively monitor large areas like parking lots, schools, and construction sites. Also, they can be used in close-up applications such as ATMs, card-locked garage entries, and multi-door entryways where both high image detail and wide field of view (FOV) are required.
Much has already been written about the factors affecting the adoption of 4K as a standard in the security industry. These typically include the cost of infrastructure and hardware. However, technological and market advances have already addressed these limitations with, for example, the introduction of H.265 compression and the rapidly declining price of 4K monitors. And with our knowledge of the speed of market adoption of HD; 4K is on course to become the next big video surveillance standard within 2-5 years.
Increased quality and resolution of these systems increases the value of that investment and the potential return it can provide. An investment in a CIF resolution video system may only guarantee a deterrent effect. However, if you are a victim of a crime you run the risk of not being able to identify the perpetrator with this type of system. By contrast, an HD system makes positive identification much more likely.
While no worldwide standard exists, the security industry seems to be heading toward adoption of the EN standard requiring 250 pixels per metre for the purposes of facial identification. Higher resolution cameras and lenses are critical to achieving this and satisfying our appetite for higher detail images.
Increased quality and resolution of these systems increases the value of that investment and the potential return it can provide. With the advent of 4K, offering four times higher the resolution and pixels on target than HD, you can expect to increase the value of your system’s investment more easily. More pixels on target, combined with content analytics, offers the potential for genuine calculation of ROI
A hexagonal hallway connects three wings at one of the oldest comprehensive high schools in New Jersey, presenting a unique video surveillance challenge. The multiple angles of the hexagonal design at Salem High School in Salem, N.J. suggested a need for more than the usual number of cameras to cover the area with lenses that could limit the views. The hexagonal hallway dilemma was just one of the quandaries solved by the selection of Arecont Vision megapixel cameras for this installation. The solution incorporates the latest camera technology offering 5-megapixel images, along with wide angle lenses that provide warp-free images that use every single dot in the 5-million-pixel image.