360 / Panoramic Cameras SelectionBy John Honovich, Published Oct 19, 2012, 08:00pm EDT
A number of important considerations should be factored in when selecting Panoramic / 360 degree cameras. Key ones include: (1) limited VMS support, (2) low light issues, (3) Wide Dynamic Range problems, (4) pixel density limitations and (5) mounting height. We examine each issue, considering the options and alternatives. For background, see our test results of 2 panoramic cameras - Mobotix and Grandeye.
VMS support for panoramic cameras has traditionally been very limited because they require special integration to handle the immersive / digital PTZ controls. While any VMS can integrate fairly easy with the video stream, to be able to control what aspect of the 360 degree image one looks at requires implementing a proprietary and uncommon SDK. Without that, the user cannot control the panoramic camera unless they switch to the web browser interface of the panoramic camera.
If you already have or are committed to a specific VMS, you should start your selection process by determining what, if any, panoramic cameras the VMS supports. Indeed a number of panoramic cameras are only fully supported by the camera manufacturer's own VMS (e.g., Mobotix).
Recently, newer providers have eliminated or downplayed the role of immersive controls, favoring a dewarped output that is easier for VMSes to integrate. For example, this is the only option for Axis's 360 cameras.
Low Light Issues
Many panoramic cameras have poor low light performance because they have high high f numbers (e.g., f/2.0 or higher is typical) and lack mechanical cut filters. This is often due to the small form factors of the mini dome housings common with panoramic cameras (examples include Grandeye, Geovision and Mobotix - though Mobotix offers a b/w only option). A few panoramic cameras support box camera models that provide mechanical cut filters (e.g., using Immervision lenses or Sentry 360's Full Sight series). However using a box form factor can take up more space and be aesthetically less pleasing.
In either case, be careful about potential low light performance issues.
Because panoramic cameras use a single imager to look in 'all' directions, the camera is susceptible to lighting variations and having part of the image either washed out or very dark. All cameras vary the exposure setting to determine how much light is gathered and can face problems if the lighting variation is too wide. However, with traditional cameras covering a narrow field of view, the probability of wide variations is lower simply because of the limited area captured. If you use multiple traditional cameras, each one can set its exposure for the light levels for its portion of the scene (e.g., long exposure for dark interior, short exposure for bright entranceway). However, with panoramic, only one exposure can be selected.
In our tests, image quality problems were common as one part of the scene regularly faced sunlight during the day while another was of a much darker interior scene. If you are OK with part of the scene being under or overexposed, this can be tolerated but it should be considered up front.
Pixel Density Limitations
While the upside of panoramic cameras is that they can look in every direction, the downside is that the same number of pixels need to cover a much much larger area. Because of this, the image does not 'look' as good as traditional cameras. In our tests, even 3MP panoramic cameras 'look' like CIF resolution with the major benefit that it is 'CIF quality' in every direction.
This tradeoff is fundamental. Let's say a panoramic camera covers the equivalent area of 6 'regular' cameras (assuming 60 degree horizontal FoV for each). This means that the panoramic camera will have 1/6th the pixel density at any given point. If you expect to see clear facial details of a person 15 feet from the camera with a 'regular' camera, you may only be able to make a rough outline at that same distance with a panoramic camera.
There's no way around this. More resolution will help moderately but this is an inescapable aspect of the technology. Avoid VGA / SD panoramic cameras unless you only want an overview camera that shows little to no fine details. On the other hand, increasing resolution from 2MP to 3MP or 5MP is likely to provide only modest image quality benefits as the additional pixels are spread out over a very wide area.
The last significant consideration for panoramic cameras is mounting height. You want the panoramic camera to be as close as possible to the people / objects being monitored. With traditional surveillance cameras, if a camera needs to be mounted far from an object, the simple solution is using a longer focal length (e.g., a 50mm lens instead of a 5mm). However, panoramic cameras do not offer optical zoom nor varifocal panoramic lenses. As such, if a panoramic camera is mounted on a 30 foot ceiling, people are going to look like ants. Either avoid such high mounts or use a extension mount to position the camera closer (bearing in mind that such mounts may be aesthetically unappealing).
In 2011, only a handful of companies make 360 / panoramic cameras:
- Immervision (their lenses can be used with 3rd party cameras)
- OnCam Global
- Sentry 360
Expect to pay an average of $1,000 per camera for those cameras.
However, in 2012, many more manufacturers have released panoramic offerings, including Axis, Panasonic and many Taiwanese manufacturers. Now with these offerings, pricing has moved down to the $500 - $800 range.
Multi-imager cameras provide many of the benefits of panoramic / 360 degree cameras with a major limitation. On the plus side, multi-imager cameras often cover 180 or 360 degrees, providing a very wide coverage area. They send out 'standard' video streams so integration is easy. Also beneficial, often each imager can set its own exposure control, reducing the above mentioned WDR risk. The major downside is that they eliminate the immersive / 360 degree controls. While you can still use digital PTZ controls like any other camera, you can not rotate or 'move' throughout the image.
There are only a few multi-imager camera options available:
Expect to pay an average of $1,500 to $2,000 for these cameras.
[NOTE: An earlier version of this note was published in March 2011 but has been revised in October 2012 to reflect new developments].
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