Page 70 - Security Today, September 2017

Why Your VMS Matters Interest in hemispheric cameras is a result of saving money
BAy Bret McGowan
s a security professional, how many times have you had to explain why a PTZ camera should always be paired with at least one fixed camera to
provide constant “back-up” coverage of ev- erywhere the PTZ is not looking?
Today, that conversation is happening far less often, thanks to the current genera- tion of hemispheric cameras—super high- resolution 360-degree cameras with fisheye lenses. For many PTZ applications, as well as situations requiring the use of several fixed cameras, a single hemispheric camera is now often the preferred solution. How- ever, in order to take full advantage of the benefits offered by hemispheric cameras, you must carefully consider the VMS being used with them. Understanding the relationship between VMS and camera is vital to ensur- ing that your investment in this technology delivers on expectations.
Hemispheric Cameras: Why and Where?
The main reason customers are so interested in hemispheric cameras is that they can save money. Investing in a VMS system can add up quickly, and an easy way to keep costs contained is reducing camera count. Using a single camera to cover large areas reduces costs in many ways: the price of cameras themselves, cabling to support them, and the associated time required for installation. There are also cost savings related to VMS licensing (only one camera license is needed, instead of several) and on-going mainte- nance and support.
Hemispheric cameras are popular in a wide range of settings, both indoor and outdoor. Schools use them in intersecting hallways where multiple cameras were his- torically installed. They also make sense in large spaces that have a defined perimeter, like cafeterias and gymnasiums. Commercial customers find them useful in areas such as lobbies or parking lots. To cover these spaces, the cameras can deliver a wide, 360-degree or 180-degree view, and allow for zooming into specific areas as needed.
Usually, they are ceiling or wall mounted, with the main difference being that a wall mounted camera can only provide a 180-de- gree view. When wall mounted, a “wedge mounting plate” is typically used, that tilts the camera downward, so that its field of
view covers the length of the wall. A less common mounting option is facing upward, either on the floor or on a table or counter top. In all situations, the compression and data rates are the same.
When choosing how many megapixels you need, keep in mind that the megapixel count refers to the entire field of view—all 360-degree or 180-degree. Bandwidth and storage will need to accommodate that num- ber. However, when you zoom in on sections of the total image, your megapixel count for that video frame is approximately equal to its percentage of the entire field of view. And, the more you zoom in, the lower the visual megapixel count becomes. So, if you’re thinking about using one hemispheric cam- era in place of four 2MP cameras, you will need at least an 8MP hemispheric to deliver
images of each quadrant with a similar level of detail.
Does Your VMS Dewarp?
When hemispheric cameras first entered the market, several years back, the VMS sys- tems on the market hadn’t been designed to deal with them any differently than “regu- lar” cameras. Therefore, the hemispheric cameras were responsible for dewarping the distorted image captured by their fisheye lens before sending it on to the VMS. This meant that the VMS recorded the video ex- actly as it was displayed. Full information available from the original spherical image was not captured.
Today, many VMS manufactures are building dewarping filters into their own software. This allows the VMS to receive a
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