Frequently Asked Questions About CCTV
1-What’s the difference between Hardware Compression and Software Compression?
Hardware Compression: Both Capturing Video Signal and Compressing Video Signal are done by DSP chipset integrated on DVR Board. It doesn’t need the computer’s CPU to do this work. It’s low cost of CPU and RAM resources. In this system the computer CPU’s task focus on answering network request, streaming the video/audio to network and saving recorded data to local hard disk.
Software Compression: The DVR Board only capture video signal but doesn’t compress it, it is the computer CPU and RAM to do this compression work. It’s high cost of CPU and RAM resources. In this system the computer CPU and RAM are often overloaded. It is easier to crash than hardware compression system.
2- How do I choose the correct camera for my application?
This in general is a comparatively difficult decision. Many aspects of the installation must be taken into consideration in order to obtain the correct performance that meets your requirements.
A high-resolution camera should be considered where greater detail of scene is required. E.g. Color 460 TVL, Monochrome 570 TVL. Choosing a more sensitive camera will improve reproduction in poorly lit areas. The sensitivity of a camera is indicated by the minimum amount of light in order for the camera to produce a usable picture. e.g. Color 1.0 Lux at F1.2.
A conventional camera produces a pale backdrop when an object is shot against a bright background. BLC (Back Light Compensation) will counter strong light sources retaining picture quality.
Concentrated light sources directed towards the camera (e.g. car head lamps) can be inverted by an optional peak white inverter or an eclipser function. This has the effect of bringing detail to areas and making an object clear, that would otherwise be shadowed.
3- How do I set up a camera and lens for use in Low Light conditions and or with Infra Red Lighting?
When setting the back focus of a Color camera for low light conditions you should place an ND1 (Neutral Density) filter in front of the lens. When setting the back focus of a Mono camera for low light conditions you should place an ND3 (Neutral Density) filter in front of the lens. When setting the back focus of a Mono camera fitted with I/R lighting for low light conditions you should place an IRP (Infra- Red Pass) filter in front of the lens.
4-Should you not have any of the above filters you may have to attend site during the hours of darkness.
I have installed a new camera and lens why I am unable to obtain a sharp image?
The most common resolve to this is to ensure that both camera and lens are the same mount i.e. ‘CS’ mount lens on a ‘CS’ mount camera and a ‘C’ mount lens on a ‘C’ camera.
What are OSD cameras?
OSD (On Screen Display) cameras have a menu system within the camera assembly that can be accessed in order to set functions such as Iris levels, AGC on/off and most features of standard and advanced cameras.
5- Why do I have a clear sharp picture during the day and it is out of focus at night?
This is due to the depth of field changing as the light conditions change and can be easily overcome by following set procedures.
6-When can I use a manual iris lens?
A general rule of thumb is only to use a MI lens in an internal application. This is because you are reliant on the electronic circuitry of the camera compensating for light changes in the scene and this is not able to compensate to the same degree as that of an Auto Iris lens.
7- How do I back focus a camera fitted with a fixed focal length lens?
This is achieved by following five simple steps.
Set the physical focus of the lens to infinity (clockwise from the front).
Aim the camera at the subject to be viewed.
Release the camera back focus mechanism.
Adjust the back focus to obtain the best possible picture.
Secure the cameras back focus mechanism.
8- Can I fit a 1/3″e; Lens to a 1/2″e; camera?
The simple answer is NO.
9- How do I connect an Auto Iris lens to a camera?
This is usually performed by a simple plug-in connection to the rear or side of the camera. However you should always refer to the relevant camera handbook.
10- What is the difference between Auto Iris and Direct Drive Lenses?
An Auto Iris lens is one that automatically adjusts its iris for changes in the scene lighting levels. The motor that opens and closes the iris is driven by an Amplifier that processes a small electronic signal changing with the light level.
A Direct Drive ‘DD’ lens does not have this Amplifier and can only operate with a camera fitted with one.
A camera specification will indicate the available output options.
11- Does the ‘f’ stop matter when choosing a lens?
Yes, lenses are usually specified as having a minimum and maximum ‘f’ stop rating; the ‘f’ stop is a measure of how efficiently the lens allows light from the scene, to pass through the lens and onto the camera CCD sensor. The maximum aperture (when the lens is fully open), is the minimum ‘f’ stop number and the minimum aperture, (just before the lens completely closes) is the maximum ‘f’ stop number.
A low minimum ‘f’ stop number means that the lens can pass more light through during dark conditions, which will produce better pictures at night.
A high maximum ‘f’ stop number may be necessary where there is a high level of light or reflection. This will prevent the camera ‘whiting out’.
12- How do I Back Focus a camera fitted with a ZOOM Lens?
This can be achieved by following these steps.
Set the lens to full wide angle view.
Set the physical focus of the lens to infinity (clockwise viewed from the front).
Aim the camera at an object at least 30 Meters away.
Release the camera back focus mechanism.
Adjust the back focus to obtain optimum clarity.
Zoom the lens in to full telephoto and focus on a nearby object.
Keep this object in view as you slowly zoom out and if all is set correctly it should remain in focus (track).
Secure the back focus mechanism.
13- How do I set up an Auto Iris lens?
An Auto Iris lens has two ‘pots’ on the side commonly marked ALC (Automatic level control) and LEVEL.
The ALC control has settings of PEAK and AVERAGE (P+A).
The LEVEL control has HIGH and LOW settings ‘H+L’.
ALC
The adjustment allows control over any bright areas in the scene e.g. sun reflection through windows, street lighting etc. There are two settings PEAK and AVERAGE.
If set to PEAK, bright areas in the scene are taken into account more, reducing the contrast in the surrounding area. This allows more detail to be seen in the bright areas.
If set to AVERAGE the lens takes the bright areas less into account which usually causes over brightness or flare in these areas, but raising the contrast of the surrounding area.