While quality and performance should be the main considerations when selling and installing video surveillance systems, the importance of cost to customers cannot be dismissed. This fact is one reason that 180- and 360-degree cameras have gained traction lately. Offering the potential of lower equipment, installation, maintenance and other costs with reduced camera counts, these cameras have become an attractive option for a variety of customers — whether they are budget-conscious or not. The quality and performance that 180- and 360-degree cameras offer doesn’t hurt their popularity either.

To provide dealers and integrators with the ability to make the best choices for their customers, SDM is taking a look under the hood of these cameras to see how they work, and to examine the pros and cons of the various technologies they employ.

Image Capture

Typically, 180- and 360-degree cameras are based on two hardware platforms: single-lens/single-sensor and multi-lens/multi-sensor. In a single-sensor camera, the imaging sensor works in combination with either a fisheye or panomorph lens to capture images, which must then be de-warped to produce either a 180- or 360-degree view.

A multi-sensor camera incorporates up to four imaging sensors, an equal number of lenses and image-processing capability within the same housing. For example, an eight-megapixel camera would consist of four separate two-megapixel modules. The images gathered by the sensors are then stitched together to generate a full field of view, but that isn’t the only approach, says Patrik Pettersson, product analyst, North America, Axis Communications, located in Chelmsford, Mass.

“A camera capable of 180 and 360 degrees may not always be used to cover those exact fields of view. Rather, they may leverage the multi-sensor capability in order to individually aim each sensor and lens combination to see specific areas of interest that are not in perfect 180- or 360-degree field of view,” he explains. “Or they can be configured for an outside corner of a building with the purpose of covering the 270 degrees of that corner, for example.”

Of the two sensor models, the fisheye/panomorph approach tends to be more widely deployed, says Tom Cook, vice president of sales for Ridgefield Park, N.J.-based Samsung Techwin America.

“It’s relatively easy to place multiple imagers into a housing to create a panoramic camera. Unfortunately, you then essentially have multiple cameras to adjust, focus and configure. Some recording platforms would see these as separate cameras, adding to the hassle and costs of camera licenses,” he says. “Now that higher-megapixel cameras can be efficiently transmitted and recorded, single-sensor panoramic cameras are becoming very popular.”

However, the image quality produced by single-sensor/single-lens cameras can be hampered by a number of issues, including limited depth-of-field, pixel density at the edges of the lens, and poor low-light sensitivity with higher-megapixel resolution, Pettersson says.

“They are not an ideal choice for a camera reduction strategy and are improperly used as an identification product when they should really be used as a complementary overview camera in most applications,” he says. “In some cases, they require good integration with video management software for de-warping purposes.”

One potential misunderstanding about 180- and 360-degree cameras is that they aren’t always separate technologies. A single-lens, single-sensor 360-degree camera can be easily transformed into a 180-degree camera by wall mounting rather than ceiling mounting it, Pettersson says.

“Top down, the camera is operating in a 360-degree capacity; when mounted on a wall — with a bit of digital cropping from the top and bottom of the image — you can transform it into a 180-degree camera,” he describes. “The single-lens 180/360 camera also covers the entire field of view, even dead-center underneath the camera, whereas a multi-sensory, multi-lens camera has a void underneath because its four lenses point out from the center core of the product, which can be adjusted by pointing the lenses down. But this setup causes loss of critical depth-of-field. The 180/360 multi-lens cameras are better at covering larger areas due to their native capability of a longer depth-of-field.”

A main difference between the two sensor approaches is that multi-sensor cameras are used more for longer views rather than capturing images directly below the camera.

“Multi-sensor cameras are generally used when you want to cover a large area in a significant amount of detail. A 360-degree single sensor is used for a smaller area to reduce camera counts or cover the entire room,” says Jeff Corrall, product manager, Edge Devices for Ottawa-based March Networks. “Too often, these cameras are lumped into the same category. You may require a 360 but don’t know whether you want a multi-sensor or single-sensor because the differences are so vast.”

In addition to lower costs, single-sensor cameras also tend to be easier to install and have a lower risk of component failure. In terms of practical applications, single-sensor cameras have limited depth-of-field, making them well-suited for providing situational awareness at shorter distances, such as mounting above a cashier or teller to monitor transactions.

“There are pros and cons to each approach. If you are using a single camera, you are using only one stream versus larger multiples of streams, which present bandwidth and storage issues to consider,” says Allen Chan, senior product manager, security, Sony Electronics, Park Ridge, N.J. “Multi-sensor is utilized more for looking farther out, as the vertical field of view is limited, while fisheye/panomorph allows you to see all around and is used more for situational awareness, including surveillance of a known entity — for example, monitoring someone on suicide watch.”

Single-sensor cameras also can suffer from inherent pixel loss based mainly on a problem of geometry, says Steve Gorski, chief sales officer for Boston-based Scallop Imaging, adding that de-warping can further compound that issue.

“The biggest disadvantage with single fisheye lenses is the significant waste and loss of pixels, up to as much as 75 percent. A camera using a fisheye lens typically projects a circular image on a rectangular image sensor. That alone results in 50 percent of the pixels being lost,” he says. “In order to create an image the human brain can make sense of, fisheye images then have to be de-warped. This de-warping process results in another 25 percent of the pixels being lost.”

Multi-sensor cameras share many of the same pros and cons with their single-sensor relatives, with a few key differences, Pettersson explains.

“These [differences] include benefits such as higher-quality lenses that provide greater image quality at longer distances and a larger platform that gives manufacturers the ability to add more capabilities onto the camera. But of course, these benefits come with a higher price tag when compared to its counterpart,” he says.

Another benefit of single-sensor cameras that may be overlooked is based on form factor. Because they don’t look like traditional security cameras, they can be placed in locations that were previously inaccessible, such as museums, hospitality, high-end residential, casinos and elevators, Cook says.

“For retail locations, you can cover many aisles with one camera, and a criminal casing the joint can’t simply look up to determine where the camera is pointed,” he says. “Multi-imager cameras can be useful for locations with fixed views, such as four-way hallway intersection to replace multiple cameras.”

Image Processing

The images generated by hemispheric views are convex, particularly at their borders. So once images are captured, they must be processed to produce a view that humans can comprehend more easily. The de-warping process employed by single-sensor cameras applies software to the raw image to correct for curvature to allow viewing of the scene from the usual perspective.

This processing can be performed either on the camera itself prior to transmission or on the client side using software once video has been transmitted to the head end. For the most part, figuring out the best approach depends on who you ask, which doesn’t make sorting out the right choice very easy.

The benefits of camera-based de-warping start with the compression that is applied to the video prior to transmission, which some experts say is much better than with client-based de-warping.

“It is very important that the de-warping take place on the raw image before compression. This ensures good image quality in all parts of the image, specifically at the edge,” says Heidi Barnum, head of internal operations, MOBOTIX Corp., located in New York.

Conversely, having access to the raw image allows for more functionality, Corrall says. “With client-based de-warping, you’re technically streaming and recording at full resolution, which allows digital PTZ in the full image,” he says. “Customers are forced to pre-select the desired field-of-view they want to see when de-warping is performed in the camera. They can select up to four views to send to the VMS, but once you de-warp at the camera, there’s no going back to other views — and there’s no way to perform digital PTZ.”

Because there is no clear-cut “right way” to perform de-warping, many manufacturers are starting to recognize the value of both approaches and, as such, are diversifying their product ranges. For example, while Hikvision’s cameras available in North America currently employ software-based de-warping, the company doesn’t dismiss image processing within the camera.

“We also promote on-board de-warping, since the video is just like any other view and is recorded as such without any special integration required,” says Bob Germain, senior product manager at City of Industry, Calif.-based Hikvision USA. “This provides great flexibility when being used with third-party video management software. It is also useful on NVRs in terms of providing direct access to the de-warped stream at the NVR itself without the software.”

 Starting with the potential to reduce camera counts, the benefits offered by 180- and 360-degree cameras are numerous. When evaluating the various models and manufacturers, the technologies cameras employ to capture and process images are the main factors to consider when evaluating 180- and 360-degree cameras. Each has its benefits and drawbacks, so it’s crucial that integrators be as informed as possible on the differences before making the right choice for a customer application.