Blog

Defining Video Surveillance Cameras Chicago Technical Security Camera Specifications

A) Capturing real-time video for Video Surveillance Cameras Chicago Technical Security Camera Specifications
Real-time surveillance requires integration of cameras and high-quality displays. In defining their needs,
users should consider whether cameras will be used for recording video stream, even if the primary
usage is in real-time (i.e. the recording could well have forensic or analytic uses down the line). Highresolution cameras require high storage demands because they record video stream and capture minute
levels of detail.
If the real-time use of the video system involves analytics (using computer processing to aid in detection
of objects, behaviors, or motion), the needs of those systems will dictate many aspects of the camera,
lens, and mount. For example, will the video system be used for detection and alert purposes if people
approach or loiter near critical infrastructure? Users must take into account factors such as how far
away the infrastructure is, how large it is, and whether it is well lit.
Storing video
Videos can be stored for possible future analysis. Proper storage is critical in evidentiary and forensic
video applications. For example, if video is stored only at a very low bit rate to save space on the
storage media, then data will be irretrievably lost. Those accustomed to storing word-processing
documents or digital photos might be shocked at how rapidly video files consume storage space, which
can range from single video cassette recorders or a single hard drive, to systems with multiple cassette
recorders or huge arrays. Depending on the frame rate, resolution, and compression of the video, a
user may need to store terabytes of data. One clear implication of this: the rules for retention, both
within an organization and the records-keeping laws in a particular jurisdiction, will affect the amount of
storage needed.
Storage is also often proceeded by some form of processing, altering the file format to fit differing
media, such as coding the video in MPEG 2 so that it can be stored on a DVD and played back with a DVD
player. A series of alterations or physical custody changes made to a video file is called the “storage
chain.” Almost every change in file format results in a loss of data, so the storage chain should be
monitored and documented very closely.

B) High discrimination of detail for recognition, identification for Video Surveillance Cameras Chicago Technical Security Camera Specifications:
For example, if the video will be used for positive identification, reading license plates, or detecting
small objects, and not for simple motion detection (i.e., did a person cross a boundary?), look for the
following features:
• High-Resolution Camera – Resolution is measured in mega pixels or lines. More megapixels or
more lines offer a greater ability to capture detail. The tradeoff for this ability is the greater
amount of data produced by these cameras can increase the need for bandwidth and storage.
• Large-Imaging Sensor – Sensor (or “imager”) size is measured in fractions of inches. Large
sensors, such as a 1/2-inch sensor, can capture more light than a 1/3-inch or 1/4-inch sensor.
If fidelity is especially important, users should pay attention to other aspects of the camera, such as the
manner in which the camera is connected to viewing or storing systems, and the compression ratio of
the video signal.
• The lens* should offer low distortion and high resolution.
• The communications network* needs to accurately transmit all signals. If digital, a highbandwidth, reliable communications network may be needed. If analog, the communications
network should have a good ratio of signal to noise.
• Compression* should be kept to a minimum, since a low compression level will result in lower
image quality. The amount of storage available and the rules governing retention of the video
can determine the amount of compression required.

C) Target Size for Video Surveillance Cameras Chicago Technical Security Camera Specifications.
Target size refers to the size of the object of interest with respect to the field of view.
Capture small or distant objects
Cameras used to record small or distant objects should have:
• Telephoto, Zoom*, or Varifocal lens – The degree to which lenses bring distant objects closer or
make objects appear farther away (but capture wide fields of view) is called the focal length.*
Focal length is measured in mm. Lenses with longer focal lengths (called telephoto or “long
lenses”) are more telescopic and can make distant objects appear larger to the camera’s sensor,
so that images will be sharper. The drawback is that the longer the lens or the more it is
zoomed in, the less field of view* the camera will capture. The advantage of a varifocal or zoom
lens is that it can act as a wide angle lens and capture a wide scene, and also zoom in on small or
distant objects. One tradeoff of long lenses is their susceptibility to capture less light, resulting
in less functionality in dark environments. Furthermore, lenses that are telephoto and admit a
large amount of light are usually large and expensive.
• High-Resolution Camera – Resolution is measured in mega pixels or lines. More megapixels or
more lines offer a greater ability to capture detail. The tradeoff for this ability is the greater
amount of data produced by these cameras can increase the need for bandwidth and storage.
• Large-Imaging Sensor – Sensor (or “imager”) size is measured in fractions of inches. Large
sensors, such as a 1/2-inch sensor, can capture more light than a 1/3-inch or 1/4-inch sensor.

D. Motion Detection for Video Surveillance Cameras Chicago Technical Security Camera Specifications.
Motion refers to the motion in the scene of interest (e.g., background, target, or camera).
Camera or objects in motion
The ability for a video system to clearly capture moving objects, or to capture scenes if the camera is in
motion, is determined by several factors. Systems are better suited for this situation if they have:
• Fast Shutter Speed – Shutter speed is the length of time that the camera sensor is exposed to
the image it is capturing for each of the still-photos that comprise the video. If there’s enough
light to do so, it’s better to have fast or “short” or “high” shutter speeds (measured in fractions
of seconds) so that while each image is being recorded, the scene being recorded on the camera
has less of a chance to move and thereby blur the image. One way to decrease the need for the
environment to be bright is to use a wide-aperture lens.
• Wide-Aperture lens – The ability for lenses to admit more light is measured in f-stops; the
smaller a lens’ f-stop number, the more light is allowed to pass through the lens. The advantage
of a smaller f-stop number is that when more light hits the sensor, the camera uses shorter
shutter speeds and takes more pictures. However, this come at a price because lens’ with small
f-stop number require wide aperture lenses, and those lens’ have difficulty keeping both near
and distant parts of the scene in focus at the same time (a quality known as depth-of-field*).
• Wide-Angle Lens – If the camera or object is moving, it’s easier to keep the camera on the object
if the lens is capturing a wider scene. This ability of a lens to capture a wide scene is a function
of its “focal length,” measured in millimeters, with smaller focal length lenses capturing wider
scenes, but making them appear smaller or farther away.
• Large Imaging Sensor – Sensor size is measured in fractions of inches. The sensor is to digital
cameras what film is to conventional cameras. Large sensors such as a 1/2-inch sensor can
capture more light than a 1/3-inch or 1/4-inch sensor.

E. Lighting Level for Video Surveillance Cameras Chicago Technical Security Camera Specifications.

Lighting level is an obvious aspect that impacts selection of video equipment and refers to light available
to illuminate the scene of interest.

Low-Light Situations
The ability of video systems to work in low light is measured in their “lux” rating. Lux is a measure of the
amount of light present; cameras that have a lower lux rating can work in darker environments.
As with high-motion applications (described in Section V. Qualitative Guidance, D. Motion) when
selecting lenses for low-light applications, try to select those with larger apertures (lower f-stop
number). The larger opening will transmit more light to the camera’s sensor. This will give the added
benefit of reducing motion-blur, since each image will be captured more quickly. In other words, users
will be able to use faster “shutter speeds.”
Camera considerations for very little or no light:
Black and White Camera: Most black and white cameras are better suited for low-light environments
than most color cameras.
Day/Night Camera: This tradeoff may not be easy, but the increasing availability of “day/night” cameras
designed for color during the day and black and white at night increases the number of options for wideranging lighting situations.
Infrared Camera: There are also cameras available that work in zero lux, or with no visible light. This is
possible because these systems are sensitive to infrared light, and they use a form of infrared lighting
that’s not visible to the naked eye.
Changing-light situations
If the video system will be used in environments where the light can fluctuate from bright to dim, be
sure to consider “auto-iris” lenses. These are lenses that automatically adjust their sensitivity in
changing light situations so that the lighting level of the video appears as even and constant as possible.

CONTACT US Today for FREE QUOTE and CONSULTATION!

or email : stevey@chicagohidef-videosurveillance.com

Leave a Reply

You must be logged in to post a comment.

Professional Best of Breed Video Surveillance & CCTV Installation in Chicago Metro Area