Fisheye cameras: leaving no blind spots in sight

In video surveillance, covering blind spots has long been a challenge. As a result, fisheye cameras offering 360-degree panoramic views have become a popular alternative for end users seeking to monitor large areas. This article discusses some of the advantages and limitations of fisheye cameras, which the user should know before selecting a model that truly fits their objectives.
Izvor: a&s International
E-mail: redakcija@asadria.com

End user organizations seeking to monitor large areas, like retail outlets, hotel lobbies or warehouses, often find themselves constrained by using conventional box or bullet cameras, which point in one direction at a time. This leaves certain blind spots that are not covered and that can be exploited by criminals. A panoramic camera offering 180 or 360-degree views, be it a multisensor camera or a fisheye camera, can address this challenge.

Benefits and Limitations
One major advantage of fisheyes over multisensor cameras is size and weight. A multisensor camera, as its name suggests, has three to four sensors in one unit and therefore tends to be heavy and bulky; some models can have 314 x 512 millimeters in dimensions and weigh 4.8 kilograms. Fisheye cameras, on the other hand, are much smaller and lighter, with the diameter ranging from 146 to 160 mm and weighing less than 1 kg. While fisheye cameras offer certain advantages, it’s important to know their limitations as well.

Specifically, they have less resolution compared to multisensor cameras. “The early fisheye cameras did not have enough resolution to see the details of person’s face unless the person was very close to the camera. The latest single IP camera solutions use 4K cameras, with up to 12-megapixel resolution,” said Bob Mesnik, President of Kintronics. However, there is a caveat with that as well. “The resolution of the panoramic camera varies from the center to the outer edge of the view,” Mesnik said. “The resolution is best at the edge and worst in the middle.” Meanwhile, the viewing distance is something that the user should also know. According to Kintronics’ calculations, a fisheye camera with 4000 x 3000 resolution and an 180-degree lens allows enough resolution to recognize a person that is less than 11.9 feet or 3.6 meters away from the camera; further away the user sees less detail.

“Single-sensor 360-degree fisheye cameras have been around for many years. The problem with panoramic cameras has always been the lack of detail available at a distance,” Mesnik said. Outdoor applications can be an issue, too. “For most outdoor applications fisheye cameras are not better than multisensor cameras. For example, a corner of a building — users will not get the depth or overall image quality that can be achieved with a multisensor. That being said, for smaller indoor rooms fisheye cameras can be superior if the application requires full coverage,” said Thomas Carnevale, Founder of Umbrella Technologies.

According to Mesnik, fisheye cameras are best at providing situational awareness for users monitoring a large area instead of complex applications such as facial recognition, for example. “Fisheye cameras are used in some commercial applications where it is helpful to see an overview of an area,” Mesnik said. “If the prospect asks for other usage, we steer them to standard cameras. For example, we sometimes need to explain that the panoramic camera is not good for facial recognition.” Or, the user can pair fisheye cameras with standard cameras to achieve better monitoring. “For example, a retail store may use the wide area view to see everything in the store while using a camera at the door to view a person’s face as they enter or leave,” Mesnik said.

Some Applications of Fisheye Cameras
Generally speaking, fisheye cameras can be used in all vertical markets, helping end users monitor large areas. According to TKH Security in a blogpost, public transportation and healthcare can especially benefit, as blind posts can pose threats to the wellbeing of passengers and patients. Another vertical cited by TKH is marine vessels. “Marine vessels are usually gigantic and complex ships consisting of many different compartments and various areas, and fisheye cameras can come in handy,” the company said. “A wide-angle fisheye camera ensures full coverage of the area, using up less of the valuable space at the same time. The on board operations manager can cover a much larger amount of areas with half or even one third of the amount of cameras normally used.”

According to Mesnik, fisheye cameras are all very similar. “It’s important to note that it’s not the cameras that are significant for a vertical, but rather the dealer/ installer’s experience. Most dealers select cameras based on the relationship they have with the manufacturer, the reliability of the cameras, the support and return policies of the manufacturer (or distributor),” Mesnik said. “The cameras they choose are also affected by the video management software that works with the camera, the pricing they can get, their installation experience and the range of models available from the manufacturer.”

A Note About De-warping
Panoramic views captured by fisheye cameras, while useful to monitor all corners of a given area, are often distorted and can seem unnatural to the human eye. This is where mapping or de-warping comes in, a technology that corrects this distorted view. De-warping is done by software that creates a corrected version of the 360-degree video stream transmitted by the fisheye camera. The type of fisheye lens plays a key role in this process. “The lens can provide stereo- graphic, equidistant, equidistant angle or orthographic images. The software mapping will be different depending on the lens,” Mesnik said. The de-warping process can be done in the camera firmware or in the supporting video management software. “Some camera manufacturers provide a software plug-in that does the mapping in the VMS. For example, Hikvison has provided software for Milestone,” Mesnik said. “A software- and-lens combination is available from Immervision. This company provides both a lens and algorithms that run in the camera. The company provides special Panamorph lenses and software that improves the quality of the video.”

Yet the user should know about some of the issues with de-warping. “Some fisheye camera manufacturers only have in-camera de-warping with no client-side de-warping ‘plug-in’ to a VMS, while others have in-camera de-warping but the de-warping algorithm is not sophisticated and the images look warped,” Carnevale said. “In addition, the video management software community is fragmented at best as it relates to true client-side de-warping of fisheye cameras. Some VMS’s have their own de-warping algorithms and others are brand- or model number-specific with an SDK integration. Still some integrations are just very generic between camera brands and video management software companies, leaving the user with heavy processing power issues with live de-warped displayed images.”

Selection and Installation Tips
The specification sheet of a fisheye camera may include a lot of information. According to Carnevale, users should look at the optics first. “Fisheye lenses are in much lower production than traditional board or P-Iris or varifocal lenses. Because of that, the quality gap is wide. This traditionally affects the image quality on the outer perimeter of the fisheye causing artifacts and uneven focus. More resolution is not always better when selecting fisheye cameras for this reason,” he said. “A close second place is low light. Evenly illuminating fisheye cameras is not an easy task. I’ve seen several models that only illuminate the image ‘straight-down’ so outside a five-feet radius the image is completely dark. Also because there are several IR illuminators focused this can cause over exposure.”

According to Mesnik, choosing the right products really depends on the customers’ own needs and requirements. “We ask questions such as what detail do you need to see? How far away do you want to be able to see a target? What are the lighting conditions? Is the camera facing a bright window that requires wide dynamic range? Do they want to view an area that is very dark?” he said. “Selecting the right fisheye camera starts with the customer’s objectives.”

Fisheye cameras are typically mounted on the ceiling to get the maximal result.

The following are some of the installation tips, according to Reolink in a blogpost:
– Avoid placing a 360 fisheye camera in or near a corner, as the walls will hinder its panoramic view.
– If the user plans to install a panoramic fisheye IP camera to the ceiling, make sure the camera is located in the center of the monitoring zone; otherwise the images will be reshaped.
– Keep the camera away from air conditioner vents and electric entrance doors.
– Make sure the fisheye camera is not near ceiling lamps or indicator light, which will interfere with the image signal and affect the camera’s image quality.
– Stabilize the 360-degree fisheye security camera with expansion screws to prevent it from falling down over a long period of time