Resolution is the ability to resolve or see distinctly small details in an image. Resolution for CCTV cameras (as well as for TV monitors and recorders) is usually specified in terms of lines of resolution. The number of TV lines in the video produced by the CCTV-surveillance camera is a measure of picture resolution. The more the lines, the higher the resolution and the better the picture quality. CCTV cameras range from 200 to more than 1,000 lines of resolution. The larger the number of TV lines, the better the resolution and the overall picture quality.
Backlight is the light behind the object of interest in a scene. This can be a major problem, especially in cameras with automatic iris control, because the camera will often adjust to keep the bright background within acceptable levels. Think about a camera aimed at a door at the end of a dark hallway. When someone opens the door and steps into the hallway, the camera will try to compensate for the sudden bright exterior background. The result will be that the person in the doorway appears silhouetted and detail is lost in “shadow.” In extreme cases, there may be no discernible detail at all. Cameras must have backlight Compensation to overcome this situation.
Backlight compensation is composed of camera circuitry that samples a scene and makes an assumption that objects in focus are the objects of interest, and that light levels should be optimized for these objects. Extremely high background light levels are selectively shut down while maintaining optimum levels on the objects of interest.
As shown in example below.
The WDR function of a camera is a technology that compensates for high contrast of light and shadow situations. This makes it possible to monitor surveillance in interior or exterior settings with dim lighting and high shadows.
Common applications where a Wide Dynamic Range Camera is best utilized include:
- Entrances where sunlight is a factor.
- Parking garages.
- License plate capture scenarios (balances out light from headlights).
Low florescent lighting (cameras are positioned near lights due to low clearance or mounting restraints).
While the WDR feature does cost a little more, it is well worth the extra money in terms of picture quality. Details in the image are maintained as light extremes are balanced, providing a far more accurate and life-like picture.
The 3D-DNR technology virtually eliminates image blur during low-light video capture which enables users to clearly capture images. Compared to the conventional 2D-DNR function, this 3D-DNR technology dramatically cleans up the noises in video frames especially when capturing moving images in low-light conditions.Additionally, the 3D-DNR technology can substantially reduce the amount of HDD storage required for DVR recording.
Used more often than lumens when discussing security cameras, a lux is a unit of illumination. It measures the amount of uniform light that falls on one square meter (expressed in one lumen per square meter). Security camera specs use the lux to indicate how much light they require to operate, with lower lux levels indicating a camera as more effective in lower ambient light also.
Direct sunlight 100,000 - 130,000 lux
Full daylight, indirect sunlight 10,000 - 20,000 lux
Overcast day 1,000 lux
Indoor office 200 - 400 lux
Very dark day 100 lux
Twilight 10 lux
Deep twilight 1 lux
Full moon 0.1 lux
Quarter moon 0.01 lux
Moonless clear night sky 0.001 lux
Moonless overcast night sky 0.0001 lux
Camera Formats (Image Sensor Size):
Common formats are 1/4”, 1/2”, 1/3”, 2/3”, and 1”. The size of the sensor directly affects the field of view obtained. When using the same size lens on different format sensors, different viewing areas are obtained. For example, using a 6mm lens on a 1/3” sensor will give you a 37º field of view. Using the same lens on a 1/2” sensor will increase the field of view to 56º and 74º on a 2/3” sensor. Always remember the larger the image sensor, the wider the view when using the same lens. We have created this chart below to help you better understand what kind of angles and distances you will capture:
Below pictures will explain the area viewed by using different size of lens at the same distance.
*Most 1/4" CCD cameras produce a significantly narrower field of view with the same focal length lens. This chart displays angles based on 1/3" image sensors.
**Due to the physical nature of lens optics, these numbers listed should be considered accurate within ±3° and therefore a few feet/meters as well. These are approximate guidelines to help select the appropriate lens for your application. Each camera will have its own unique field of view depending on the lens. Also, the C- & CS-mount lense will typically have a slightly narrow field of view compared to our board lenses.
CCTV Lens Calculator
Choosing the correct lens for your surveillance application can be one of the hardest and sometimes most confusing decisions to make when selecting the correct camera for your purpose. When you're looking to capture a wide area, such as a full parking lot, you will not be able to capture extreme details at far away distances. Even though some cameras have higher resolution than others, sometimes it's still hard to see exactly what you need to. However, please note that the better the resolution, the more likely you are to capture the extra detail that will help you identify more detailed characteristics in a scene. The better the camera, DVR resolution, frames per second, and monitor, the better the footage will be.
For a quick 1/3" Camera, you can work out the lens required using this simple method:
Distance from object multiplied by 4.8,divided by horizontal or vertical area tobe viewed equals the lens reqd.d x 4.8 / A = L.
e.g. To focus on an area 5m wide from a camera installed 20m away would be: 20 x 4.8 / 5 = 19.2.
So you would need a lens with a focal length of 19.2mm.
Below pictures will explain the area viewed by using same size of lens at the different distance.
A Pan Tilt Zoom Camera (PTZ Camera) is another great solution. As the name suggests, these cameras will allow you to not only zoom into an area but remotely control it to pan and tilt as well. This will give you the advantage of controlling the camera in order to point it exactly where you need it. Some PTZ Cameras even come with an auto tracking feature which will automatically follow an object or person dependant on how sensitive you set the cameras sensors.
One other factor that will affect the type of view you get will be the size of the image sensor on the camera itself.
CCTV resolution is measured in vertical and horizontal pixel dimensions and typically limited by the capabilities of both the camera and the recorder that you are using for your CCTV surveillance installation. CCTV systems use an analog video signal. For television specifications (which CCTV uses) the higest resolution that can be captured and stored is 704 x 480 (NTSC system) and 720 x 576 (PALsystem). This resolution is knows as D1 resolution. A high end CCTV recorder is capable of recording at up to D1 resolution.
QCIF QCIF (Quarter Common Intermediate Format) - 1/4 of CIF video resolution.
CIF CIF (Common Intermediate Format) - CIF is also known as Full CIF (FCIF) to distinguish it from Quarter CIF (QCIF).
HD1 Half of a D1 resolution is 704 ÷ 2= 352 still retains the vertical line format.
DCIF: DCIF(Double Common Intermediate Format). Specifically,DCIF is the same number of pixels (168,960) as 2CIF, but DCIF is stretched horizontally.
2CIF: 2CIF (2 Common Intermediate Format).
D1 :D1 can also represent the following video resolutions:
720x480 (TV/DVD-Video NTSC)
720x576 (TV/DVD-Video PAL)
960H :A unique, uncommon format only obtainable from a capable DVR and compatible camera.
What is 960H?
960H is a new standard for security cameras and security DVR's that provides high resolution images using advanced image sensors. Security cameras capable of 960H produce an image that is 960 horizontal and 480 vertical pixels large (960x480).
What are the benefits of 960H?
- Higher Resolution Recording: Security cameras and DVR's capable of recording at this resolution provide superior images that are 34% larger than D1 and more than 500% larger than CIF.
- Better Image Quality: Recording larger images provides a greater amount of image detail. Images are sharper and it is easier to distinguish objects that are close together.
- True to Life: 960H creates a wide-screen picture that does not need to be stretched to fit wide-screen TV's and monitors.
- Easy to Upgrade: 960H systems use the same BNC video cabling as lower resolution systems. If you already have a security camera system, upgrading to 960H will save you time and money compared with IP camera systems that require rewiring.
What do I need to do to take advantage of 960H?
To take advantage of 960H recording, you will need security cameras that are capable of producing 960H images and a security DVR capable of recording at 960H resolution.
I already have a security camera system. Will my old equipment be compatible ?
960H security cameras and DVR's are backwards compatible with standard resolution cameras and DVR's. However, both your security cameras and DVR must be 960H capable to get the improved picture quality and performance. 960H cameras will provide a good picture on a standard resolution DVR, but they will perform even better with a system that can support the full image size.
All your existing BNC video cables are compatible with 960H DVR's and security cameras. To upgrade to 960H, simply replace your existing DVR and cameras.
Important Key points for Installation of CCTV system.
Before delegating what camera to buy or how many, stop to think about what is most crucial to your needs. Are you installing a Security Camera System as a preventive measure? Is it as an answer to watch and catalogue a record of events, either home or business? Is it a retaliation move to show you will no longer be a victim unwittingly in your absence? Or are you seeking that peace of mind remote viewing and recorded documentation brings? Asking yourself can help you better strategize your angle of interests and focus on the importance of the task at hand. Here are some key points that might help you achieve this mindset:
I. What are the possible points of entry of the business, development, or home.
(Don’t forget about the best escape route for a perpetrator to escape the scene from).
II. Would license plate captures benefit you in the occurrence of an event .
III. How many entrances and exits are there near high priced inventory.
IV. Are there any high traffic areas (such as check-in desk, drive thru, register, driveways etc.?)
V. Where have past break ins or criminal activity occurred.
VI. Where do children mostly congregate.
VII. Where has the vandalism mostly taken place.
VIII. What areas could prove to be potentially hazardous (such as pools, playgrounds, stairs, gym equipment etc.?).
IX. What are areas that are annoying/illegally violated (such as dumpsters, parking spaces/lots, private property, etc.?).
X. Where are people more susceptible to be preyed upon like schools, parking lots, playgrounds, after hour bars, strip clubs, concert stadiums, public transportation waiting terminals, etc.?