How to Choose CCTV Cameras

How to Choose CCTV Cameras

Cameras for CCTV systems are available in several different styles - commonly referred to as Bullet, Dome, Eyeball (aka Gimbal), Box or Body cameras, PTZ (Pan, Tilt and Zoom), and Covert.

The cameras can have various attributes such as Resolution, Lens options (fixed or vari-focal), Infra-red lighting, Weatherproofing, and Vandal resistance.

All the various options can make the task of choosing the right camera for the job a tad confusing. But if you go about it logically you should end up with the correct camera.

Just bear in mind that the more features the camera has the more expensive it is likely to be. Also remember that there are a lot of cameras coming from the Far East, a lot of which seem to be over-hyped on their specifications and of dubious quality. The latter is the main reason we choose to use Hikvision as our supplier of cameras as well as DVRs and NVRs.

Internal or External

All external cameras can also be used internally, but internal cameras are generally less expensive.

Camera Types

A lot of the time the choice of camera will be based on aesthetics or ease of installation.  See the article on [link]Cabling and Connections

Dome Cameras

Dome cameras have the lens (and IR LEDs if fitted) on a gimbal enclosed within a clear or smoked plastic dome (see picture). When a smoked cover is used it is difficult to see where the camera is pointing. They are usually fitted internally and can be ceiling or wall mounted. They are available with fixed focal length lenses - typically 3.6mm and vari-focal lenses - typically 2.8 - 12mm. See below for an explanation of lenses.  They can be mounted directly onto the ceiling or wall.  They can also be fitted using brackets.  The bracket improves the cable management.  If brackets are not used then a junction box may have to be used.

Eyeball Cameras

LED Eyeball Camera EXIR Eyeball Camera

Also known as Turret cameras, these are similar to Dome cameras but the lens and IR LEDs are fitted within a ball which sits into an orbital socket (see picture).  The camera shown has a long range EXIR IR unit fitted instead of the LED array shown in the Dome camera above.  Again they can be mounted directly onto the ceiling or wall.  They can also be fitted using brackets.  The bracket improves the cable management.  If brackets are not used then a junction box may have to be used.

Bullet Cameras

Bullet cameras are usually fitted externally.  They are usually somewhat easier to install and are easier to position to cover the require area.  They can be fitted with power input boxes or junction boxes for cable management.

PTZ Cameras

PTZ (Pan, Tilt & Zoom) cameras are sophisticated units having motors to control the Pan (horizontal), Tilt (vertical) and Zoom functions.  Typically the cameras can pan 360 degrees and tilt 100 degrees.  They can optically zoom to around 25x and can usually digitally zoom about 15x.  The PTZ functions can be controlled from the DVR/NVR, from a PC or Mobile viewer or from a dedicated PTZ controller.

Other Cameras

There are other cameras such as box or body cameras, pinhole, and covert cameras.  At the present time (summer 2015) these camera types are not commonly available in HD-TVI or HD-IP versions.

Resolutions

Standard analogue (D1/960H) resolutions are normally quoted in TVL (TV Lines).  D1/960h systems cannot resolve video better than 700TVL.  Analogue cameras will be seen quoted at up to 1200TVL, which is obviously a bit of marketing hype - a 1200TVL camera is no better than a 700TVL camera.  Note, if you are happy with the poor resolution of D1/960H then shop around and you will pick up some great deals as sellers try to unload their stocks.

With analogue HD systems and HD-IP systems it is better to quote the resolution in pixels.  In analogue HD systems two available resolutions are quoted -720P and 1080P. 

Analogue HD (HD-TVI, HD-CVI, HD-SDI, HD-AHD)

The table below shows the number of pixels captured by both D1/960H and analogue HD.

Pixels CapturedNotes
D1345,600
960H460,800960H is simply the wide-screen version of D1.
720P921,600
1080P2073,6001080P is known as full HD and has more than 4x the resolution of D1/960H.

IP-HD

IP-HD systems use digital image capture and can capture images up to 5Mp.  The limit that can be displayed on a monitor or TV screen is 1080P ~ 2Mp.  However, the pixels are still present and the higher resolution comes into play when the image is digitally zoomed.

The table below shows the number of pixels captured by IP cameras.

TermPixels (W x H)Total PixelsNotes
1.3Mp1280 x 10241,310,720
2Mp1600 x 12001,920,000
3Mp2048 x 15363,145,728
5Mp2592 x 19445,038,848

Lenses

Typically, non-PTZ cameras are fitted with fixed focal length lenses or vari-focal lenses.  The common fixed focal length lens for Hikvision TVI cameras is 3.6mm, and for vari-focal 2.8-12mm.  The common fixed focal length lens for Hikvision IP cameras is 2.8mm or 4mm, and for vari-focal 2.8-12mm.

The table below gives the image area captured for various focal lengths at sample distances up to 30.5 metres from camera to subject.  The figures may alter slightly for lens sizes other than 1/3". 

1/3" CCTV Lens Chart – Field of View










Wide Angle















-Down To-


















Telephoto

Lens Focal Length

Camera's Viewing Angle

Distance Between Video Camera and Video Subject Area

1.5m

3.0m

4.6m

7.6m

15.2m

30.5m

mm

Horiz

Vert

Diag

H area (m)

V area (m)

H area (m)

V area (m)

H area (m)

V area (m)

H area (m)

V area (m)

H area (m)

V area (m)

H area (m)

V area (m)

2.80

109°

82°

136°

4.3

3.2

8.5

6.4

12.8

9.6

21.3

16.0

42.7

32.0

85.4

64.0

2.97

104°

78°

130°

3.8

2.9

7.5

5.9

11.3

8.8

18.8

14.6

37.5

29.3

75.0

58.5

3.60

74°

56°

92°

2.3

1.7

4.6

3.5

6.9

5.2

11.4

8.7

22.9

17.4

45.7

34.8

3.70

72°

54°

90°

2.2

1.7

4.5

3.4

6.7

5.0

11.1

8.4

22.3

16.8

44.5

33.5

4.0

67°

50°

83°

2.0

1.5

4.0

3.0

6.0

4.6

10.1

7.6

20.1

15.2

40.2

30.5

4.30

63°

47°

78°

1.9

1.4

3.7

2.8

5.6

4.2

9.3

7.0

18.6

14.0

37.2

28.0

5.0

50°

38°

64°

1.4

1.1

2.9

2.1

4.3

3.2

7.2

5.3

14.3

10.7

28.7

21.3

6.0

42°

32°

53°

1.2

0.9

2.3

1.8

3.5

2.7

5.8

4.4

11.6

8.8

23.2

17.7

8.0

32°

24°

40°

0.9

0.7

1.8

1.3

2.7

2.0

4.4

3.4

8.8

6.7

17.7

13.4

12.0

22°

16°

28°

0.6

0.5

1.2

0.9

1.7

1.4

2.9

2.3

5.8

4.6

11.6

8.5

16.0

16°

12°

21°

0.4

0.3

0.9

0.7

1.3

1.0

2.1

1.7

4.3

3.4

8.5

6.7

25.0

11°

8.4°

14°

0.3

0.2

0.6

0.4

0.9

0.6

1.5

1.1

3.0

2.1

6.1

4.3

50.0

5.5°

4.2°

0.1

0.1

0.2

0.2

0.4

0.3

0.6

0.5

1.2

0.9

2.4

1.8

Site Survey

The first step in choosing a CCTV camera is to carry out a site survey to identify the area that you want to view/record.  See the article CCTV Site Survey for more information.  Ideally you should take accurate measurements and draw a plan of the areas you want to cover.  Note that you are allowed to view public areas such as the street outside your property but you are NOT allowed to view neighbouring private properties without express permission to do so.  Many modern CCTV cameras have 'Privacy Masking' which allow you to mask areas viewed by the camera such that the camera does not see them.  Once you have decided on the area you want to cover you need to consult the table above and choose a suitable focal length to give you the correct coverage.

Choose the Focal Length

For a given camera resolution, the higher the focal length then the narrower the field of view is. Standard cameras for general viewing are usually supplied with either fixed focal length lenses varying between 2.8 to 4.0mm, or vari-focal lenses which are manually adjustable between 2.8 and 12.0mm. Cameras with vari-focal lenses are more expensive than cameras with fixed focal length lenses.

PTZ cameras usually have a massive optical zoom range with focal length lenses variable typically from 4mm to 100mm – a 25X magnification. Remember that with optical zoom, the camera captures the same no of pixels. If you look on YouTube you will see the capabilities of PTZ cameras. Some PTZ cameras have an auto-tracking feature which will automatically track a moving object. Most PTZ cameras can also be pre-programmed via the DVR to pan, tilt and zoom to a time schedule.

The other variable that affects the choice of focal length is the degree of recognition required. For a given camera resolution, as the degree of recognition required increases so does the focal length of the lens: effectively narrowing the area of coverage. This may result in either more cameras being necessary to cover an area and provide the required degree of recognition or to increase the resolution of the camera.

ID Recognition

Note that when choosing cameras based on their resolution, you will have to make sure that the DVR is actually capable of processing the video.

When designing your CCTV system you need to decide what degree of recognition you need to record. In some cases you may have to use two cameras to capture the information you want.

It’s all about Pixels. The more pixels available at the point of focus then the higher the degree of recognition. As a general guide, the number of pixels per metre (px/m) for various levels of recognition is as follows.

  • Monitor (23 px/m): General human or vehicular traffic flows - no serious detail when digitally zoomed.
  • Detect (36 px/m): Man sized targets large enough to be detected but not identified, no significant detail when digitally zoomed.
  • Observe (59 px/m): Clothing & colours become distinctive, no good detail of man-sized target when digitally zoomed.
  • Recognize (115 px/m): High degree of accuracy identifying and separating known individuals – good detail when digitally zoomed.
  • Identify (150 px/m): Establish identity of individuals beyond shadow of doubt - excellent image when digitally zoomed.

For example using the Field Of View table above, a camera with a 3.6mm lens has a horizontal view of 11.4 metres at a distance of 7.6 metres (25 feet). If we use an IP camera with a resolution of 1.3Mp, the horizontal resolution is 1280 pixels. Dividing 1280 by 11.4 metres gives a result of 112 px/m. The table below shows a comparison of various resolutions based on a camera with a 3.6mm lens at 7.6 metres.

Resolution

Horizontal pixels

Pixels per metre

720P

1280

112

1.3 Megapixel

1280

112

2.0 Megapixel

1600

140

1080P

1920

168

3.0 Megapixel

2048

180

5.0 Megapixel

2592

227

 

Indoor & Outdoor

For indoor use the common choice is a dome type camera, with or without IR lighting, although you may find it difficult to source cameras without IR lighting.  The main drawback with dome cameras is that to adjust the cameras viewing area, the camera has to be disassembled to adjust the lens gimbal.  Eyeball cameras can be adjusted more easily, and bullet cameras can be adjusted fully.  Indoor cameras are usually fitted to ceilings or high up on walls and as such the cabling is relatively simple to install neatly without the need for waterproof junction boxes.

For outdoor use, the common choice is the bullet type camera, although external eyeball and dome cameras are available.  External bullet cameras are relatively easy to fit and they are available with compatible junction boxes and can also be pole mounted.  Bullet cameras are also usually fitted with sunshades which help to reduce the back-lighting effect when the sun is behind the viewed scene.

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