Technical Support

Day-Night Security Cameras

Day-night cameras, also called low-level cameras, employ a very sensitive digital chip that can capture scenes in very low-level lighting conditions. During the day, the camera takes images in color while at night it automatically switches to black-and-white mode when the light level drops a certain amount. These cameras do need some light in order to take images, even if it is the light of the moon or stars.

Some people confuse day-night cameras with infrared cameras but they are not the same. The latter use infrared illumination for their operation to see without any light at all.

Outdoor Security Cameras

Outdoor security cameras are housed in special weatherproof enclosures or housings that protect them from tough weather and temperature conditions such as rain, snow, wind and the sun. Some enclosures utilize electric strip heaters and fans. The strip heaters help keep the humidity down for the electronics, prevent condensation from forming on the housing cover and camera lens, and provide heat in cold environments.

Other security cameras meant to be placed in high-crime or high-vandalism areas feature tough "armored" enclosures that can withstand heavy blows.

Dome Camera

Dome cameras gets their name from the plastic dome housing that the camera is enclosed in. They are most often seen in retail businesses and office buildings. Often the dome is dark tinted making it hard to see where the camera is pointing.

Dome security cameras are very tough and some models come with high-impact polycarbonate housings that will withstand heavy blows, making them ideal for locations with high-potential vandalism.

Bullet Camera

Bullet cameras are shaped like cylinders, and get their name from the fact that they resemble bullet cartridges. Bullet cameras come with weatherproof housings and are often used as part of outdoor CCTV surveillance systems.

Most bullet cameras have a fixed 4mm lens. A 4mm camera lens lets you to see facial features out to approximately 35 feet. A 4mm lens allows provides about a 70° viewing angle, which is the widest angle you can have without suffering picture distortion.

Hidden Spy Cameras

Hidden cameras, also called spy cameras or covert cameras, are designed to be very small and either hidden from view, concealed in everyday objects, or disguised.

Most hidden camera are pinhole cameras, which feature a small lens that can see through a tiny pinhole opening, such as behind a wall.

 

 

Choosing the Right Security Camera

Application. Ask yourself for what purpose you intend to use a security camera or camera system for: real-time viewing, store surveillance (which means recording and storing video footage), one room of a house, access doors for an office building, etc.

Color vs. B&W. How important is it to have camera images in color? Black-and-white security cameras generally have greater sensitivity at low light levels and thus are cheaper than an equivalent color cameras.

Indoor vs. Outdoor. If the camera is mounted outdoors, be sure and get an appropriate enclosure for the environmental conditions likely to be encountered. This can include rain, snow, heat, cold, sun glare, humidity and corrosive atmosphere.

Fixed lens vs. zoom lens. Fixed-lens cameras are much cheaper than zoom lenses. Ask yourself how important it is to be able to remotely zoom in or out a scene.

Fixed mount vs. pan-tilt camera mount. Similar to the lens issue, ask yourself how important it is to be able to move the camera up, down, or side to side.

Note: One pan-tilt-zoom (PTZ) camera can replace the job of several fixed mount, fixed lens security cameras.

Open vs. hidden camera. Do you care if the security camera is visible or is covert operation of the camera important?

Real-time vs. later viewing. Do you need to be able to view camera images in real-time or is storing images on a video recorder for later viewing acceptable?

Local viewing vs. remote viewing. Do you want to be able to view images from anywhere? This would mean getting a network IP camera that can be accessed over the Internet.

Some factors about CCTV Cameras

Part 1: CCTV Camera Recording speed


Video recording capacity and its after the fact usability is governed by one main factor among all others: recording speed. Recording speed in short determines how much data is gathered and how quickly it is gathered. The slower a recorder records, the longer a time period can be stored in the same amount of storage space (such as an 80G drive). When you capture less data, there is less data to store. So by slowing down your record rate, you increase a given unit's ability to archive more data, and thus get a longer length of total time from the same amount of hard drive space. However, taken to extremes, slow record rates can be so slow that the desired information is missed in between recording intervals (such as very fast and slight hand movements or cars that speed through entrances). Spy Centre Security recommends security level video recording to be 5 frames per second or better for most situations.

Part 2: CCTV Camera Image size


The next main factor that affects the total storage ability of a DVR is the size or resolution at which the video is recorded. The larger the image that is recorded, the more each individual clip takes up on the hard drive. However, small pictures may not contain enough image resolution to clearly display fine details. For example, facial recognition or license plate recognition might be difficult on a video clip recorded at 320 x 240 resolution. Although many DVRs have the ability to digitally zoom an image after the fact from the video playback archive, this effect tends to distort the picture as it gets bigger and bigger, rendering most fine detail blurry and undecipherable. It is always better to record your information at a higher resolution initially, as opposed to trying to digitally zoom in to it after it is already recorded. The last thing to note is that a 640 x 480 resolution picture is actually 4 times the size of a 320 x 240 picture because both the length and the width of the picture are doubled. All things being equal, this means that a 320 x 240 resolution archive will be about 4 times the the archive length (in days) of the same footage that was recorded at 640 x 480 resolution. Generally speaking, Spy

 

Part 3: CCTV Surveillance Camera Lens size and camera field of view


The lens size quite simply determines your field of view. Field of view directly affects the usability of playback video. Most of the time, security camera coverage shots consist of three "typical types" of shots: facial recognition, license plate recognition, and wide general coverage shots. Facial recognition and license plate shots need to have the desired object fill at least 50% of the shot or more to capture the detail necessary to identify the object properly. That generally means that the field of view needs to be about 4 to 8 feet wide to yield useable detail. Wide shots are not really concerned about fine detail so much as viewing width. Typically the widest shot possible is the goal. Taken to extremes, wide-angle shots have next to no recognizable detail and are mostly just monitoring general movement. Trying to pull a face or a license plate out of a wide angle shot at a long distance is all but impossible. After-the-fact digital zooms will distort the picture and destroy any detail their may be. The first step in determining the appropriate lens size is to determining the viewing distance (or focal length) to the desired object. Most standard fixed lens bullets and domes have an approximately 4.0 mm lens by default.
 
CCTV Surveillance camera field of view width

 

Distance to target object in feet

Lens

10 15 20 30 40 50 60 70 80 90 100 110 150 200 300
3.6 mm 10 ft 14 ft 19 ft 29 ft 38 ft 47 ft * * * * * * * * *
6.0 mm ** ** 9 ft 12 ft 18 ft 24 ft 30 ft * * * * * * * *
12.0 mm ** ** ** 9 ft 12 ft 15 ft 18 ft 21 ft 24 ft 27 ft 30 ft 33 ft * * *
25.0 mm ** ** ** ** ** ** ** ** ** 9 ft 15 ft 18 ft 21 ft 29 ft 43 ft
* Field of view at this distance and lens size is too wide for most applications
** Field of view at this distance and lens size is too narrow for most applications

 

Part 4: CCTV System lighting and the camera scene


Scene lighting is the last major component in video usability. In short, if the lighting is too low for a given camera, it cannot "see" the scene properly. This effect results in an all black image that is wasted and unusable. Many different types of cameras exist and each is geared towards one main type of ambient lighting situation. Extreme cases require the ability to see an absolute darkness and require special types of cameras. For example, a small storage closet with a safe inside, or a server room with no overhead lights would require an infrared camera to record much of anything. In general, using a camera with the lowest possible light rating is the most desirable.
There is one main exception to this rule of thumb though: license plate recognition in low light or darkness. License plates are designed to be reflective so they can be seen at night when car headlights make them "light up". Infrared cameras work because they illuminate the scene with a type of light the human eye generally cannot see, however the image sensor of the camera can. Unless the camera in question is a very special type of infrared, this results in the camera projecting light out on to the plate, the light reflecting back at the camera, and thus causing the license plate to appear as a big white blob.
 
LUX and low lighting chart

Ambient Condition

Illumination

Range Details

Foot candles LUX
Sunlight
Full Daylight
Overcast Day
Very Dark Day
Twilight
Deep Twilight
10,000
1,000
100
10
1
.1
107,527
10,752.7
1,075.3
107.53
10.75
1.08
Daylight
Range
Full Moon
Quarter Moon
Starlight
Overcast Night
.01
.001
.0001
.00001
.108
.0108
.0011
.0001
Low Light
Level Range