Security Camera Glossary of Terms
A 3-Axis Gimbal is a lens mounting system inside dome cameras, which allows you to easily position the lens to almost any angle.
Adaptive Tone Reproduction (ATR/ATR-EX)
A feature of the Sony CCD, ATR and the more advanced ATR-EX, improves the contrast of images that contain both very bright and very dark areas, producing greater visible detail in each extreme.
See Automatic Electronic Shutter
See Automatic Gain Control
The alarm is a system that detects an event and sends a trigger signal to initiate a particular action. In most cases, the alarm detects motion and the trigger initiates DVR recording of the image from the camera that generated the alarm trigger.
See Automatic Light Control
The aperture is the opening in the lens that controls the amount of light that passes through to the image sensor. The size of the aperture is controlled by the iris in the lens.
See Adaptive Tone Reproduction
See Automatic Tracking White Balance
See Automatic White Balance
The iris controls the aperture size, which determines the amount of light that passes through the lens to the image sensor. An automatic iris is automatically adjusted to produce the proper image exposure, based on the amount of available illumination.
Automatic Electronic Shutter (AES)
When using a fixed or manual iris lens, the camera's AES circuit can adjust for moderate changes in illumination levels by slowing down or speeding up the shutter speed. When AES is off the shutter speed is set to 1/60th second for NTSC and 1/50th second for PAL systems. When imaging fast moving objects a higher shutter speed can cause "freezing" effect, which can improve clarity on the moving object.
Automatic Gain Control (AGC)
The Automatic Gain Control is a electronic circuit that automatically adjusts the video gain based illumination level. In low-light conditions, the gain is increased to ensure sufficient brightness for image clarity.
Automatic Light Control (ALC)
When using an auto-iris lens, the ALC circuitry samples the illumination level and automatically adjusts the iris to create the proper sized aperture for proper exposure.
Automatic Tracking White Balance (ATW)
A specific form of AWB, ATW continually tracks and adjusts the white balance, making it suitable for use in cameras in which the image content and lighting are subject to changes.
Automatic White Balance (AWB)
When activated, the AWB function detects white in the captured image and adjusts the color/white balance accordingly. It then saves the setting and does not adjust white balance again until the AWB is reactivated. AWB is best suited for scenes with a constant background and lighting.
Automatic White Balance Control (AWC)
A specific form of AWB, AWC uses a "preset" white standard to which it constantly adjusts as lighting conditions change. To set the AWC, hold a white card in front of the camera and press the AWC set button. The camera will register that color as "white" and will adjust the white balance accordingly.
See Automatic White Balance Control
Back Light Compensation (BLC)
In situations in which there is a bright light behind the subject of an image, the bright light would normally saturate the image, causing the subject to be seen in silhouette. The BLC circuitry adjusts the exposure so that the subject is properly illuminated and clearly visible. The BLC system operates in a similar fashion to WDR (Wide Dynamic Range), but lacks its ability to compensate for both excessive and insufficient subject lighting.
See Back Light Compensation
See Lens Mount
Charge Coupled Device. The video image sensor chip. The CCD and its accompanying storage memory is the functional equivalent of physical photographic film.
Closed Circuit Television. Another name for video surveillance systems.
A measure of the mixture of color and white elements in an image. An image with high saturation has little or no white elements.
See Lens Mount
A Day/Night camera is one that can be used in normal and very-low light conditions. This is accomplished either by adjusting the light sensitivity of a single image sensor or by switching between two sensors tuned for normal and low-light conditions. While a Digital Day/Night camera can capture images in very low-light conditions, it cannot capture images in no-light (0 Lux) conditions.
A True Day/Night camera improves on the basic Digital Day/Night functionality with the addition of infrared (IR) LEDs, which provide IR illumination for clear images in no-light (0 Lux) conditions.
Dead Pixel Compensation (DPC)
The DPC circuitry allows the camera to detect the presence of dead or stuck pixels in the image sensor and compensate for any that will not change color.
The Demist circuitry digitally sharpens an image that is being degraded by atmospheric conditions (e.g., fog, rain, haze, dust, etc.) or even a dirty/dusty lens.
Digital Image Stabilization (DIS)
The Digital Image Stabilization system compensates for camera vibration, shaking, or other minor movements caused by wind, booming bass, or other local conditions. It works by creating pixel buffer and storing extra pixel from outside the main video frame. It then dynamically adjusts the image positions based on the movement of visible objects in the image, filling in the necessary portions of the image from the pixel buffer.
Digital Noise Reduction (DNR)
Image noise can come from a variety of sources, but is most often associated with low-light conditions, resulting in a "grainy" image. This noise not only interferes with the ability to clearly distinguish individual image elements, but also increases the storage space required for any given image. The DNR circuitry uses a digital comb filter to remove this noise. A 2D filter removes most graininess from images, moving objects can produce image blur trails. A 3D filter improves on the results of a 2D filter by eliminating motion blur, as well as image noise.
Digital Signal Processing (DSP)
Digital Signal Processing is a generic term to describe the various digital filters and compensation circuits that process the captured image to produce image clarity, proper color balance, subject illumination, etc.
Digital Slow Shutter (DSS)
As the name implies, the DSS circuitry is used to slow the shutter speed to allow more light to reach the camera's image sensor. This improves clarity in low-light conditions and can eliminate the need for artificial lighting.
Digital Zoom is a system by which an image is enlarged by cropping the original image, then using pixel interpolation to fill out the spaces between the original pixels to produce a zoomed image at the full resolution. While digital zoom can magnify an image, it does so at the expense of clarity.
See Digital Image Stabilization
See Digital Noise Reduction
See Dead Pixel Compensation
See Digital Signal Processing
See Digital Slow Shutter
A dual voltage camera is capable of being powered by a 12VDC or 24VAC source. It automatically switches to the appropriate mode based on the connected power source.
See Electronic Light Control
Electronic Light Control (ELC)
When using a fixed or manual iris lens, the camera's ELC can adjust for moderate changes in illumination levels. While it is fine for indoor applications in fixed illumination conditions, a fixed iris and ELC circuitry cannot approach the range of illumination usable with an auto-iris lens and ALC circuitry.
A flickerless setting on a camera sets the synchronization signal to twice the frequency of the AC circuit. The sync signal is therefore at 100Hz for PAL systems and 120Hz for NTSC systems.
The focal length is the physical distance between the center of the lens and the focal point, which is the image sensor on a digital camera. As focal length increases, the magnification of the image increases, but the field of view correspondingly decreases. Conversely, a shorter focal length provides less zoom, but also a wider field of view.
To help determine the best focal length for your situation, first measure the width of the object you want to see or area you want to cover and the distance of that object/area from the camera. For a camera with a 1/3" CCD, use the following formula to determine the optimal focal length:
Optimal Focal Length = 4.5mm x Distance to Subject / Width of Subject
You can use any unit of measure for the distance and width values, so long as they are the same.
The f-number, also known as the f-stop, is a measurement of the optical speed of a lens, which is the speed at which the lens collects light. The smaller the f-number, the faster the lens collects light, allowing for the use of faster shutter speeds. The effective f-number of a lens is determined by the iris and the size of the aperture. The f-number of a lens is calculated as:
F-number = Focal Length / Lens Diameter
H.264 is an advanced video compression standard used for high-definition video sources. It is a block-oriented motion-compensation-based codec and is one of the codec standards used for Blu-ray Discs. As with all MPEG-based codecs, the data stored consists of an initial image, with subsequent frames containing only the portions that changed from one frame to the next. Because each movement or video change is recorded, excessive video noise can drastically increase the size of stored videos.
See High Light Compensation
High Light Compensation (HLC)
In situations in which there is a bright light in the foreground, the image exposure would normally be reduced, resulting in a darkened background. The HLC circuitry acts top diminish the intensity of the close, bright light, allowing the overall image exposure to be increased to where the background can be clearly distinguished. The HLC system operates in a similar fashion to WDR (Wide Dynamic Range), but lacks its ability to compensate for both excessive and insufficient subject lighting.
See Infrared Cutfilter Removal
Infrared Cutfilter Removal (ICR)
The CCD in a Day/Night camera is capable of receiving and imaging both normal light and infrared light. When operating in color mode during normal lighting conditions, the infrared cut filter is used to eliminate any IR element from the image. When illumination levels drop and it switches to Black & White mode, the IR cut filter is removed, which greatly improves the sensitivity of the CCD and allows it to produce a clear image.
Ingress Protection Code
See IP Code
IP Code (Ingress Protection)
The IP Code is an international standard for declaring the level of protection against the ingress of water or foreign materials of a particular enclosure or case. The number listed after the IP designator is a two digit number, with the first digit indicating the level of protection against solid particles and the second digit indicating the protection against liquids. A rating of IP66, for example, indicates that the enclosure provides complete protection against dust and protects against "powerful water jets" from any direction.
True Day/Night cameras include LEDs, which produce infrared illumination for use in low-light conditions. The number of IR LEDs is directly related to the level of IR illumination available and the maximum illumination distance.
The iris is the mechanism within the camera lens that allows it control the size of the aperture, which allows light to pass through to the image sensor. The iris in a lens can be controlled manually or automatically.
The Lens Mount is the means by which the lens is physically and electrically connected to the camera body. There are two common lens mount types in use for security cameras:
A C-Mount is a 1-inch diameter threaded mount with a depth of 12.5mm and a pitch of 32 threads-per-inch (TPI). a 5mm spacer, known as a C-ring, is required when attaching a C-Mount lens to a CS-Mount camera body.
A CS-Mount is a 1-inch diameter threaded mount with a depth of 17.526mm and pitch of 32 threads-per-inch (TPI). A CS-Mount lens cannot be used with a C-Mount camera body.
A lumen is a measure of the amount of visible light emitted by a light source.
Lux is a measure of the amount of illumination in a given area. One Lux is equal to one lumen per square meter. Lux is short for luminous flux. For reference, direct sunlight can produce as much as 130,000 lux and typical office lighting is in the 500 lux range. At the dark side, a full moon on a clear can produce as much as 1.0 lux while a clear night illuminated only by starlight produces about 0.0001 lux.
The min lux level is the minimum level of illumination needed to produce a clear video image. Day/Night cameras have minimum lux ratings for both color and B&W modes.
Minimum Object Distance
The minimum distance at which a lens can focus on an object. Lenses with short focal lengths can focus closer than lenses with long focal lengths.
Mirroring is the ability of the camera to digitally flip the image in the horizontal, vertical, or both dimensions. Vertical mirroring is useful for situations in which the camera is mounted upside down, while horizontal mirroring is appropriate when the primary image is viewed through a mirror.
See Minimum Object Distance
As the name implies, motion detection is the ability of a camera or DVR to detect movement and respond accordingly. Motion detection can usually be limited to a portion of the camera's field of view and is usually used to trigger the DVR to start recording. The use of motion detection based recording allows you to save disc space and time reviewing security footage by only recording when a potential security related event occurs.
Multi-streaming is the ability of a device to simultaneously output two or more video streams. In most cases, the purpose of this is to produce a high-bitrate stream for viewing on a monitor, plus a low-bitrate stream for viewing on mobile devices.
The negative feature allows the camera to capture images in the negative, with the white and black levels reversed. The result is a negative photo image.
On Screen Display (OSD)
The On-Screen Display, or OSD for short, is the built-in menuing system, which allows you to configure and control a given device. Cameras, monitors, and DVRs usually each have their own OSD.
See On Screen Display
Pan, Tilt, Zoom (PTZ)
PTZ refers to the ability of a camera to adjust its pan (horizontal), tilt (vertical), and zoom from a remote location (e.g., computer, DVR, mobile device, etc.).
Passive Infrared (PIR)
The term Passive Infrared refers to the sensor used in motion detectors. The sensor works by establishing a baseline or "normal" sensing field, then reacting to any changes in the IR signature of that field. Even when a moving object has the same heat signature as the background, the change will be detected as motion. The PIR is usually used as a trigger for an alarm signal, which in turn usually triggers recording of the image from the detected camera.
PIP is a process by which a second video stream is superimposed over a small portion of the primary video stream. This results in the primary image filling the screen with the secondary image presented in a small box in one corner of the screen.
See Passive Infrared
Privacy masking is the ability to specify a portion of the field of view to be blocked or masked from view and recording. When applied to a camera that is capable of PTZ operation, the privacy masking is accurately maintained even as the field of view and zoom levels are varied.
See Pan, Tilt, Zoom
Sens-Up (aka Sense-Up)
See Digital Slow Shutter
The shutter is the element within the camera that rapidly opens and closes to expose the CCD and create a frame of video. The speed of the shutter directly affects the amount of light that can reach the image sensor. Slow shutter speeds are appropriate for low light conditions, while fast shutter speeds are best for bright conditions.
Signal-to-Noise Ratio (S/N Ratio)
As the name implies, this is the ratio between the amount of signal that represents the video you want and the noise you don't want. S/N is expressed in decibels (dB) and the higher the number the better quality of the resulting video signal. A value below 40dB is usually considered to be too noisy, values above 60dB are usually considered to be extremely clear, and values in between represent acceptable, but not exceptional, video quality.
SLR (Strong Light Reduction)
Sometimes also called HLC (High Light Compensation), SLR is the masking of a very intense light source such as car headlights in order to bring up detail in the normally lit areas, such as a license plate or face.
See Signal-to-Noise Ratio
The video signal on a camera is always synchronized to some point. For single camera installations, an Internal Sync is sufficient. However, when viewing multiple cameras on the same display, it is necessary for the cameras to be synchronized together. To accomplish this, you can either use a sync signal that gets sent to each camera, known as External Sync, or synchronize the cameras to the AC power cycle, known as Line Lock.
Tracking has several meanings in relation to security systems:
- The ability of as zoom lens to maintain focus throughout the entire zoom range.
- The ability of a PTZ camera system to adjust the field of view to maintain coverage of a subject as it moves out of the frame.
TV Lines (TVL)
The TVL resolution is a measure of the number vertical lines that can be clearly distinguished across the width of the display. A large TVL number indicates a large number of pixels used to display the image, which translates directly into image clarity. Most dual-mode cameras have one TVL value for color and another, higher value, for B&W mode.
As the name implies, a varifocal lens is one in which the focal length can be infinitely varied between an upper and lower limit. On a security camera, a varifocal lens allows you to dial in the exact amount of zoom and field width needed for any given coverage area. See Focal Length for more information about the effects of focal length.
See Wide Dynamic Range
Wide Dynamic Range (WDR)
While BLC can produce clarity in objects in shadow, it often washes out the lighted background. Similarly, while HLC can reduce the intensity of bright spots in the foreground, it can dim the background too much. WDR improves on the ability of BLC and HLC light level compensation by independently adjusting the intensity of different portions of the image to produce proper lighting intensity across the entire image.