How To Select Perfect CCTV Security Camera Systems - Complete Guide

CCTV- Closed Circuit Television or video surveillance market has become the fastest growing segment of the security industry today. Whether it is used in a business or a residence. There are many types of cameras available in the market like Dome, IR, PTZ, Bullet etc. of different technical specifications. These cameras can be classified into two main categories, 1. Analog cameras and 2. IP Cameras also known as digital camera. Sometimes it's not an easy task to select right cctv camera. So for these reasons I am going to explain How To Select Perfect CCTV Security Camera Systems and its components so you can improve customer relations and increase job profitability.

Step 1. Sketch and Make a Note

First of all make a sketch of your site where you are planning to work. After that, make note of some important points like which areas are important to cover, any specific door to cover etc. Just make a simple note. This time, don't think about distance, height, darkness etc. Simply do your first step.

Step 2. IP or Analog Camera

The analog cameras transmit an analog signal which requires digitization by DVR and IP CCTV cameras transmits digital signal over an IP network and doesn’t require digitization process for recording. IP cameras transmit digital signal video and image quality is much better than analog CCTV cameras. But these are highly expensive.

So, if you are securing any home in an inexpensive way, then analog might be an option.. If you’re securing any business and have an expansive area to secure, you might find IP a better solution.

Step 3. Fixed or Variable Camera

Both types have its own value. This type of camera remains focused on one field of view. While variable cameras, PTZ (pan, tilt, zoom) Camera can pan (move left and right), tilt (move up and down), and zoom in or out. These cameras can rotate in 360 degree. PTZ cameras can also provide automatic touring from one end to the other.

Step 4. Indoor or Outdoor

Its very simple step to decide indoor or outdoor cameras as its name is suggesting itself. Outdoor cams are all whether proof cameras. Bullet cams are used for outdoor.

Step 5. Selection of Lighting Issues

a). IR (infrared)-   

Very popular in domestic and small commercial CCTV applications. When light levels drop below a certain level the camera's infra red LED's allow the camera to continue recording in black and white color footage even in complete darkness.

b). Digital Noise Reduction (DNR) - 

Image noise is interference in the video signal that shows up as grainy specks. It can be caused by low lighting situations, a nearby power interference, heat, or device algorithms. Digital Noise Reduction (DNR) removes noise artifacts from signal, improving the performance of motion detection.

c). Wide Dynamic Range (WDR) -

When there are both very bright and very dark areas simultaneously in the field of view of the camera, then object will not be clear as it needed. So, with WDR, you can get clear images.

  

d). Digital Slow Shutter (DSS) -  

Digital Slow Shutter (DSS) technology improves the light sensitivity of the camera and extends its usable range. 

e) Lux Value 

LUX is used to describe the capability of a camera in low light. The amount of light is defined by LUX (lumens per square meter). One LUX is the amount of light cast by one candle at one meters space. 

• Full sunshine 10,000 LUX
• Well- lit office 500 LUX
• Comfortable reading 300 LUX
• Cloudy 100 LUX
• Twilight 10 LUX
• Dusk 1 LUX
• Full moon .1 LUX
• Quarter moon .01 LUX
• Complete darkness 0 LUX

6. Resolution 

Resolution is the "Overall picture sharpness" and it's measured by counting horizontal lines (horizontal resolution) and vertical lines (horizontal resolution) of an image. TVL  is  measurement of analog cameras and pixels is measurement of digital or IP cameras.

TV Lines (Analog) vs Pixels (Digital Resolution)

Resolution (TVL or TV lines) is a monochrome specification that states how many black and white lines can be seen in a given area.

NTSC Analog Video

An NTSC analog video picture is composed of 480 active horizontal lines. When the picture is sent to a monitor or another receiving device, the first field of 240 even-numbered lines is sent, and then the second field of 240 odd-numbered lines is transmitted. This occurs at a rate of 60 fields per second.

The odd and even fields are offset one line apart, so when they are viewed in rapid succession (60 fields per second), they slot into one another to give the illusion of the complete picture-also called a frame, which is made up of 2x240 (or 480)lines. This is called interlaced video.

Pixels

A pixel is the smallest element of a digital image. A megapixel (MP) is one million pixels, and is a specific measurement of digital resolution.

Ex: If a camera outputs a signal that is 1280x1024 pixels, it's shooting at a megapixel resolution of 1280x1024=1,310,720 pixels=1.3megapixels(MP)

It's impossible to give an exact correlation between an analog and digital resolution,  640 pixels gives a conversion to 480TVL(to work out the conversion the equivalent TVL is 75% of the number of pixels in this area 75% of 640).

For example if you are recording at 640x480(VGA resolution) you have 640 horizontal lines of pixels by multiplying to 75 you get 480 meaning that to get the best detail possible at VGA resolution, you need a camera that captures 480TV Lines or better.

7. How to choose a CCTV Camera Lens?

Focal Length

The focal length (measured in “mm”) of a lens determines how far the camera can see.

a short focal length (e.g. 2.5mm) = a wide angle of view
a long focal length (e.g. 16mm) = a narrow angle of view

The smaller the focal length, the wider the field of view.

Fixed (mono), Varifocal Lens and Zoom Lenses

A Fixed lens means the camera lens has fixed focus length. Fixed lens is generally cheaper than Varifocal lenses.
Varifocal lenses, which will allow you to adjust the focal length manually. Varifocal lenses will usually have a range, like 2.5-6mm or 5-50mm. 

 Zoom lenses are similar to varifocal, except the focal length will adjust electronically, thus they are generally more expensive.

Auto or Manual Iris

For changing light conditions, like outdoors cameras an auto Iris lenses are needed.
For indoor use manual iris lenses are sufficient as light levels will not vary too much.

F Stop(Aperture rate)

Aperture is the camera’s ability to gather light which is measured in F numbers. Both are inversally proportional, means for larger value of F number, lens aperture will be lower.

C or CS Mount

The difference between the two is simply the distance between the lens and the ccd image sensor. 

C Mount – 17.5mm

CS Mount – 12.5mm

Camera/Image format

Have you notice that CCTV cameras list either 2/3”, 1/2”, 1/3”, or 1/4” for their CCD image sensor. This is related to field of view. The larger the image sensor value, the larger the field of view.

Depth of Field

The Depth of View is the distance within which objects in a picture are in focus.

A large Depth of Field means almost all objects in the Field of View are in focus.

A small Depth of Field means only a small section of the Field of View are in Focus.


The following factors can lead to a greater Depth of Field:

• Using a Wide Angle Lens 
• High F-Stop 
• Using an Auto Iris 
• Camera Format 

The size of the camera’s CCD image device will affect the angle of view. CCTV Cameras come in different chip sizes – 2/3″, 1/2″, 1/3″ and 1/4″.

Approximate Horizontal angles of view for CCD

Focal length             Chip Cameras

                              2/3"   1/2"   1/3"   1/4"

2.0 mm                  --      --        --       82

2.8 mm                  --      --       86       57

4.0 mm                  --     77       67       47  

4.8 mm                 83     67       57       40

6.0 mm                 70     56       48       32

Video or Direct Drive

The majority of CCTV Cameras will be able to use both types. Video Drive Lenses contain circuitry which converts video signal from the camera into iris control. Direct Drive Lenses require the cctv camera to contain the circuitry.

CCTV Lens Calculator

For a quick 1/3″ CCD 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 equals the lens required.


d x 4.8 / A = L

e.g.

To focus on an area 3m wide from a camera installed 15m away would be:

15 x 4.8 / 3 = 24

So you would need a lens with a focal length of 24mm

I'll add some more tips soon...