SPARSH: dependable security solutions for developing tomorrows!

1 Black and White cameras work well in low light conditions.
Color cameras are good for identification (i.e. color of car, clothes, hair, etc) these cameras need adequate lighting.
Day Night cameras have the best of both worlds. They are color when there is adequate light and switch to black and white when the lighting gets too low for color. They have infrared illumination which allows them to see in total darkness.
Varifocal cameras have manually adjustable lenses and are used for monitoring specific points up close (i.e. cash register, door, gate, etc)
Pan Tilt Zoom cameras allow you to move the cameras remotely as you wish. They are controlled through Digital Video Recorders.
Dome cameras are used when you do not want the cameras to be so conspicuous.
Spy cameras are used where you do not want anyone to know cameras are present.
Vandal Proof cameras are used in areas where tampering is a probability (i.e. schools, laundry-mats, prisons, etc).

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. Colour 540 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. Colour 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 seen clearly with Number Plate Reader (NPR) Camera.

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. For e.g. by using IR corrected lens in place of conventional CCTV lens.

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.

How do I back focus a camera fitted with a fixed focal length lens?

This is achieved by following five simple steps.

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.

What is an Auto Iris Lens?

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.

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’.

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.

LEVEL

The only correct way to set the VIDEO LEVEL is by the use of an oscilloscope, for most Engineers this is not an option.
A more practical method is to use a service test monitor and a camera that you know has been set up correctly to 1 volt peak to peak.
Put the video output from this tested camera into the test monitor and adjust the contrast and brightness until you are satisfied with the picture. Mark the contrast and brightness controls so that you can set them to this position again.
Set up each camera adjusting the ALC (as above) then adjusting the LEVEL to obtain a picture similar to that achieved with the test camera. (Making sure that your test monitor is set to your marked positions)

NB: On most zoom lenses the ALC adjustment is a speed control for the Iris motor and is best left in the mid position. The Amplifiers on Auto Iris lenses are sensitive; so adjust the LEVEL and ALC with a proper trimming tool instead of an ordinary screwdriver, which can induce small voltages.

What size monitor should I be using?

The correct size monitor is dependent on its use e.g. the number of images to be displayed at any given time, the viewing distance and the available space.

What is Video Termination?

This is the end of line resistance of any CCTV system and this should be set to 75 ohm. Should you encounter any double image or ghosting this is more often than not caused by two pieces of equipment in series both having the 75-ohm switch set on. Only the last piece of equipment should be set at 75-ohm.

What camera housing should I use and at what IP Rating?

Camera housings come in various shapes and sizes. With regard to the correct IP rating protection, this will range from dust and water ingress. This system is governed by a number of European and British standards.
IP55

What is the difference between Standard VHS and SVHS recordings?

In general the main difference apart from cost is the increase in overall resolution. A standard VHS machine may achieve in the region of 300 TVL (mono) whereas S-VHS machines may achieve in the region of 400 TVL. However this being achieved will depend on the correct ancillary equipment being used.

What type of illumination can I use with colour cameras?

Only lighting within the visible wavelength should be used with colour cameras. Tungsten Halogen is often the recommended source of lighting.

Can I use I/R Lamps with colour cameras?

The answer to this is a definitive NO. Colour cameras are typically fitted with an IR cut filter and will not allow IR light in excess of 700Nm to pass resulting in the camera performing poorly in these circumstances.

What is an ISDN Telephone Line?

An ISDN (Integrated Services Digital Network) Line is a digital system allowing a camera to be updated at a rate of 15 frames a second.

What is a PSTN Telephone Line?

A PSTN (Public Switched Telephone Network) Line is an analogue network allowing a camera image to be updated every few seconds and is therefore slower than that of an ISDN network.

What is an ADSL Line?

Also known as Broadband, an ADSL (Asymmetric Digital Subscriber Loop) line is a form of Digital Subscriber Line in which the bandwidth available for downstream connection is significantly larger than for upstream. Although designed to minimise the effect of crosstalk between the upstream and downstream channels this setup is well suited for web browsing and client-server applications as well as for some emerging applications such as video on demand.

What is a Leased Line?

Leased Line, sometimes known as Kilostream, Megastream or Private wire. This is NOT a dial up line but is connected 24hrs a day and is usually subject to an installation charge and a quarterly bill.

Do I have to use a Regulated Power Supply?

What is the maximum distance I can run 12vdc when powering a camera?

This is a commonly asked question and there is no simple answer. Some manufacturers may recommend that their cameras can be run over (X) distance with (Y) cable. This however should still be considered as a general guide. Cable conductor size and installation route must also be taken into consideration. If you are unsure, we would recommend that you contact Technical Support for guidance.

What is a ground loop?

An AC current that can be produced in a cable. This is usually caused by parts of the system being fed from different electrical sources resulting in different earth potentials at each end. The result is interference on the signal, usually in the form of dark bands across the monitor and on occasion tearing in the top third of the image.

How can I eliminate ground loop faults?

This can be achieved in a number of ways, the easiest of which is the installation of a Ground Loop Isolation Transformer. This is best installed at the monitor or recording end of the system.

What is the correct level for a video picture?

The correct level is 1 volt peak to peak. This can only be accurately set either with an oscilloscope or with a video level meter.

How often should I replace my video tapes?

In general it is recommended that all video tapes should be replaced after a period, no greater than 20 passes of each tape. That being 10 record and 10 play back. This will also be dependent on the quality of tape being used and that the recording equipment is in good operational condition.

Manual or Auto Iris Lens?

The iris is the part of the lens that determines how much light falls upon the camera CCD sensor.

The Manual Iris 'MI' lens has this fixed at the time of installation. As the light levels change in the scene, the lens can do nothing to prevent either too little or too much light entering the camera. Virtually all cameras employ an Automatic Electronic Shutter 'AES' to compensate for these variations when fitted with an MI lens. However they are only able to cope with a relatively small change in light levels.

An MI lens should never be used in an external situation, as the camera will be unable to cope with large changes in light levels. Use an Auto Iris ‘AI’ lens in this case, or indeed anywhere where large scene illumination changes take place.

If the standalone DVR hangs at DVR loading screen, it could be because of one of the following:

If the problem persists, it needs to be sent back to an authorized service centre for doing default factory settings.

The overall bad experience in the video output is due to the Backlight effect and varying light condition due to glass. The light conditions in front of glass and outside on the other side of glass are different. This effect in picture is due to two different light conditions in same scene.

Our Bravura-540 TVL OSD camera series with enhanced feature of "Selective BLC" can address such an issue specially faced in Jewellery shops, entry/exit gates of a building/office or a glass window is there separating outside sunlight and inside fluorescent/tungsten light.

The other option to better the video output as well if you change the position of the camera and install it in another position where the backlight effect do not hinder with the video output of the camera.

IR Camera not covering proper distance or the IR Camera picture is not good in dark?

When camera is used with 3.6 mm lens, the IR LEDs of different angles have to be used. For e.g. In 10 mtr. IR camera, default lens used is 6mm and the LEDs used are with angle of 60 degrees. If same 10 mtr. IR camera is used with 3.6mm lens, LEDs used are with angle of 80 degrees. In both cases the numbers of LEDs remain same but due to change of Lens which results in change of LEDs with wider angle, the IR distance decreases.

FAQs