Infra red frequency

[Matty F]

I bought a Sony 30GB HDD Handycam DCRSR42E which has something called Super NightShot. It has a built-in LED that works well in pitch darkness for up to about 3 metres. I want to take pictures of people doing graffiti and vandalising the neighbourhood, but they are always further away, like 10 to 30 metres. I'm quite happy to have some kind of infrared spotlight but I don't understand what frequencies these things work on.

My neighbour has a cctv with infra-red LEDs that reach 30 metres, but my handycam doesn't seem to see the light from his LEDs. Does anyone know how these things are supposed to work and why this one doesn't? I can't find sensible info on the Sony.

[Dave Plowman (News)]

You can buy high powered infra red lights designed for security cameras. But like any lighting, the larger area it covers the more energy it will take.

[Matty F]

The amount of energy doesn't matter. My neighbour's infra red lights reach the desired distance. Distant objects show perfectly on his TV screen. So why doesn't my Sony using Super NightShot work with his infra red lights? If I point the Sony right at his light I just see a small amount of light coming from it.

[Andrew Gabriel]

Just make sure you're sitting down when you get the price...

In many cases, these simply run a 50W halogen lamp with a visible light absorbing coating on them. The really expensive ones are a discharge lamp.

[Matty F]

I am intending to use a 500 watt halogen lamp, when I get a filter for it. And I was going to use a "million candlepower" spot, with a filter. But the question that I am asking is why the Sony doesn't seem to see infra red light except that put out by its own infra red LED.

[Dave Plowman (News)]

If money is no object buy an infra red camera designed for the purpose.

[Matty F]

The Sony is designed for the purpose. But it doesn't work. If nobody has any brilliant suggestions I suppose I could contact Sony. I am thinking there must be a fault with the camera.

[EricP]

Google on it. There seem loads of people asking the same type of questions. I even found a YouTube video on an accessory lamp. You might get some help there.

[Alan]

In message , Matty F wrote

Have you fitted any filters yourself to the front of the lens? If so it may be these filters cutting off the IR.

[Matty F]

No I have not fitted any filters. It doesn't make sense unless the Sony IR frequency is a lot different from the security camera IR.

[Grumps]

When you try and use your neighbour's illumination, do you have your Sony set in Super NightShot mode?

[Dave Plowman (News)]

You mean it can only be used for infra red stuff? I thought it was a general purpose camcorder with some night vision capability. A very different beast than an infra red only camera.

Could be that, of course. But you suggested it works ok with its built in lights?

[OG]

Look for the HVLIRM Infra-red NightShot light for Handycams with accessory shoe adaptor This claims to increase the NightShot range up to 30 metres (though not recommended above 20 metres) £50 from Sony

[Matty F]

Yes of course! I've found a bit of info here:

don't understand why I cannot buy a still camera to do what I want, which is to take photos in near darkness, using an IR spotlight if necessary. Camera manufacturers deliberately use a filter to exclude IR. All the sites that describe how to remove that filter suggest putting a visible light filter in its place. But why? If there is any visible light then why exclude it? I am only interested in using the camera at night.

[Simon]

The reason for wanting either visible light or infra-red but not both is because the refractive index of the glass in the lens varies with wavelength. This means that the various wavelengths of radiation from a point source will be brought to a focus at different places, not all of which will be in the plane of the sensor. In other words, the image will be blurred.

The fourth picture from the bottom at

shows what happens if you try to operate a webcam in daylight with the IR-cut filter removed. I'm not sure how much of a problem this would be at night.

[Van Helsing]

Infra red is not a single frequency, its a range of frequencies much wider that that of visible light (violet red).

Many digital devices are able to see in the near infra-red, i.e. just outside the visible spectrum and use filters to block it out. This allows conventional cameras + suitable infra red light source to take pictures of people without them realising 'cos they cant see the infra-red light.

Using infra-red to create heat pictures uses the mid infra-red range - way outside the range range of your typical consumer equipment.

Your problem may be simply that your camera and your neighbours light are not operating in the same part of the IR band. Do you have any documentation that indicates teh Nightshots sensitivity range andthe output range of the lights?

[Andrew Gabriel]

Bare in mind that a filament lamp is much more efficient in producing IR than visible. You probably won't need anything like that power.

[Andy Burns]

Well it does, inverse square law and all that, but ...

... the wavelength of the IR *also* matters. Sounds like your neighbours LEDs and camera are matched, but his LEDs and your camera (or the IR filters within it) are not, IR LEDs are available from 750nm to perhaps

1550nm (wavelength is more common term than frequency for opto-electronics)

I think the super night mode is also restricted to certain exposure values so as not to turn clothing see-through under bright lights.

[Steve Firth]