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Megapixel and HD Cameras
“Megapixel” (MP) refers to cameras having arrays with a minimum of 1 million pixels, and at the present
time includes cameras with up to 120 million pixels. At the present time there are no agreed industry
standards for megapixel cameras.
Megapixel cameras offer many advantages, especially for situations where image zooming of defined areas
is required, and where doing this electronically replaces pan-tilt-zoom (PTZ) cameras. The increased pixel
count of a MP camera improves resolution while enabling an operator to zoom on an image to obtain details
equivalent to VGA and SVGA resolution. Person identification and license plate recognition are two
applications where this feature can be important. Moreover, electronic imaging zooming can be performed
on stored video streams, for post-situation analysis, which is not possible with images recorded by PTZ
A single fixed MP camera equipped with a wide angle lens, or with a motorized zoom lens, may be able to
monitor large outdoor areas, such as parking lots, or long indoor terminal concourses, which otherwise
would require multiple fixed cameras. A MP camera can do this because the video image can be zoomed
electronically and still yield acceptable image quality on the user’s monitor within a defined field-of view
(FOV). A fixed megapixel camera, however, does not have the flexibility of a PTZ unit which can change
the FOV to accommodate changing situations.
Some MP cameras also enable an image-within-an image to be created in real time, i.e., the user can
designate an area of interest in the FOV and magnify an object in that area while still viewing the entire
field coverage in the background, thereby retaining situational awareness across the area under surveillance.
Zooming in on an object with a PTZ camera, by contrast, narrows the field coverage with a corresponding
loss of situational awareness.
MP cameras may not perform as well as standard cameras under low-light conditions or in the presence of
very bright lights. This experience is changing as camera technology improves, so megapixel cameras
should be tested under all expected lighting conditions before making a selection. Where night surveillance
is required, MP camera performance can be enhanced by uprating local lighting systems, which is often
less expensive than using intensified cameras or thermal (infrared) imagers.
For higher resolution applications, many security camera manufacturers now offer HD cameras as well as
megapixel cameras. The selection of one or the other format depends on the application and system design
requires consideration of the additional storage capacity required as well as the possibility of operating at
reduced frame rate.
Wide Angle and Multi-Imager Cameras
MP cameras have led to the development of wide-angle coverage cameras, usually dome configurations,
containing multiple cameras (thus know as multi-imagers) or using one MP camera with a fisheye lens.
Sophisticated software is then used to reduce image distortion (dewarping) and to combine the video from
multiple cameras into a single visual presentation (stitching).
Multi-imager and fisheye cameras are complex units for which industry-wide standards for imager
configurations, detector sizes, software dewarping and stitching, etc. do not exist Manufacturer
specifications do not, and cannot, completely describe the imaging presentations of these cameras. For this
reason should they be subjected to real-world evaluations during the design process and selection process.
Properly used - and the design trade-offs can be challenging - such cameras might enable a few ceiling-
mounted and/or wall-mounted units to replace multiple fixed cameras with considerable cost savings in
cameras, their cabling, and video management licensing fees.
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