Security Camera Specifications Defined:
Whenever you purchase any security camera it will come with some kind of specification sheet – or if you are thinking about making a purchase, you need to know what you are getting. How will you know that the camera you are about to order will do what you need? What is LUX, AGC or BLC?? Here is where we will attempt to educate you on these specifications. It is important to consider your application when making the selection. If you are a home owner, certainly your requirements will be far less than that of a large business.
LUX Rating: The LUX rating basically tells you how well the camera will perform in low light conditions. The lower the number of the LUX rating, the better it will see at night. The LUX rating is a way to measure the sensitivity of a camera. In another words it means, how well the camera can still see image. However because there is no ISO standard to regulate a LUX rating,each major CCD maker have their own way of testing the sensitivity of their CCD. However a camera specified as ( 1 lux, F10 ) can be exactly same as the a camera specified as ( 0.01 lux F1.0 ) The most common way to measure minimum illumination is called target illumination. Target illumination means how much light is received by the plan where CCD surface is located. Although the definition is clear however there are three major parameter will dramatically changed the result of the measurement.
Color temperature: Color temperature is the way to express the spectrum contain of the light source. An light source of 3200k contain mostly spectrum around 600nm to 900nm, and a light source of 9300k contain mostly spectrum around 300 to 500 nm. hence different color temperature will totally altered the testing result. A light source with 600 nm wave length will generate 10 times more electron the a light source with 900 nm wave length light source on a typical CCD sensor, hence is 10 time more sensitive. This is why that color temperature must be specified to make the reading meaningful.
IRE level: Maximum amplitude of video output from a CCD camera normally should be set at 100 IRE or 700mV. A video in 100 IRE means that it will fully drive a monitor to expressed best image with best brightness and contrast. a video with 50IRE means it have only half of the contrast. and 30 IRE mean 30% of original amplitude or 210mV. It is generally acceptable that 30 IRE is a minimum value for a meaningful image. A regular camera will have noise level on 10 IRE while AGC kick up to max gain, hence will provide 3:1 or 10dB S/N ratio for a barley acceptable image. A reading measured under 10 IRE will be 10 times better then measuring read under 100 IRE. so a reading without defining IRE level is actually useless.
Reflection ratio: Reflection ratio of the object and it's background will significantly distort the measurement. An object with 100% reflection rate will generate 100 times more light on target plane then an object with 1% reflection rate.
BLC: BLC stands for Back Light Compensation. It is typically used in all CCD based security cameras & will automatically bring more detail to darker areas of an image when bright light shining from behind obscures it. A perfect example of this is when you have a camera pointed at a window in which a lot of light is shining through. When someone walks in the door with the light behind them, the image of the person is a black silhouette – you cannot see the person’s face but you can see everything around them. The electronic shutter of the camera basically adjusts its exposure to try to allow for more light to be allowed in the darker areas. Most of your better security cameras will have this feature available that you can turn on or off.
AGC: AGC or Automatic gain control takes action to increase the amount of image amplification in conditions to bring the video signal up to the minimum required level. Aside from increasing picture signal, AGC act as well to reduce noise and picture attenuation, and the signal to noise ratio reduced and provide quality picture, where a camera without AGC will not be able to produce a working signal. When security cameras produce a quality picture, it needs a sufficient amount of light to produce a minimum acceptable picture, In cases when the light condition is reduced to a certain level, there is insufficient light to the security camera to create a quality video picture. This is where the AGC level compensates for this lighting condition.
DNR: DNR is a circuit of digital noise reduction, able to reduce image noise such as static and improve the failure of mixture of colors and contract of colors. This is a feature that you will find among security cameras that are of a higher quality.
Voltage: Right off the bat you are going to recognize that there are power requirements for the security camera. It will either be 12v, 24v or it will accept BOTH 24v & 12v. One thing to keep in mind is if you purchase a 12v powered security camera and connect it to a 24v power supply you will burn up your camera and some of the circuits will definitely “pop” with the stinky smell of smoke emanating from your camera. Also, it is very important to keep in mind those security cameras that have IR LED’s will always pull more amperage than your typical security camera. If you have more than 24 IR LED’s, you will need to make sure that your power supply will provide at least 1 amp or more.
Wide Dynamic Range or WDR function is intended to provide clear images even
under back light circumstances where intensity of illumination can vary
excessively, namely when there are both very bright and very dark areas
simultaneously in the field of view of the camera. WDR enables the capture and
display of both bright and dark areas in the same frame, in a way that there are
details in both areas, i.e. bright areas are not saturated, and dark areas are
not too dark. WDR
cameras are commonly used in surveillance cameras and in some medical
applications. In surveillance, WDR allows a camera to filter the intensebacklight surrounding
a subject and thus enhances the ability to distinguish features and shapes on
the subject. WDR cameras are usually recommended for situations where light
enters a premise from various angles such as a multi-window room. A camera
placed on the inside of the room will be able to see through the intense
sunlight or artificial light coming in. If an indoor security camera is pointed
towards a window or an entrance door, you will see the background washed out
during daytime. This is very common situation in restaurants and stores which
have big glass windows. The
WDR function is typically found in security cameras that are more expensive than
most. However if you have a security camera that features the WDR feature, you
can readily see a difference in image quality.
DSP or Digital Signal Processor is a type of microprocessor that is typically
found on security cameras that are of a higher quality than most. The DSP
feature will take a digital video signal and process it to improve the signal
quality. The improvement will usually result with it being much crisper with
IR LED’s or Infrared Light-Emitting Diode is a feature that you will find on
security cameras that are designed to see at night in low light conditions. Most
cameras do not have a LUX rating low enough to be able to see in complete
darkens. However if your camera has IR LED’s then you can accomplish this. The
light that is emitted from an IRLED cannot be seen by the human eye. However if
you look directly into the IRLED security camera, you will notice a faint red
glow. IRLED’s are rated in Nanometers. The lower the number, the more visible
the light is to the naked eye. Most IRLED cameras are in the 850NM range which
means that you can see the red light when looking directly into the security
camera. If you have an application that requires that you cannot see the IRLED
light, such as in a covert or law enforcement application, you will need to
select a 950NM rated camera. The only drawback on this is that since the NM
wavelength is much tighter, the 950NM light will not travel as far as the 850NM.
S/N Ratio: S/N Ratio or Signal to Noise ratio means how much video signal to noise is present. This signal noise is basically electronic noise that is present to some extent in all video signals. You can identify this signal noise as snow or graininess over the whole picture on the monitor. There are several sources of noise such as poor circuit design from a cheaper security camera, heat, over-amplification, external influences, automatic gain control, transmission systems such as microwave, infrared etc. The important factor that determines the tolerance of noise is the amount of noise in the video signal, the signal to noise ratio. Note that every time that a video signal is processed in any way, noise is introduced regardless, so it’s something to be reasonably expected in most security cameras.
Microphones & Audio Recording
United States Codes, Title 18, Section 2510 (2) states:
Oral communication means any "oral communication" uttered by a person exhibiting an expectation that such communication is not subject to interception under circumstances justifying such expectation.
By definition of the code section, a person cannot have an expectation of privacy, nor can he or she expect that communication will not be intercepted, if there are public signs posted, indicating that the communication is being monitored.
The First Amendment of the Constitution provides that any conversation between individuals is private, unless otherwise notified. In simple terms, this means that any overhearing or recording of a conversation is illegal ...unless both parties are aware that it is being done.
In order to comply with the law, LOUROE ELECTRONICS provides a disclaimer stating, AUDIO MONITORING ON THE PREMISES. These disclaimers must be affixed, in plain view, to all entrances where the microphones are installed.
It is suggested that distributors notify customers, at the time of installation (or sale) of the equipment, that disclaimers must be in plain view at all entrances and exits.
In that some state laws may vary, it is further suggested that you consult with your local attorney, and become fully aware of the local laws in this regard.
Federal Law References: