Infra Red or IR response is necessary to allow cameras to see well during low light conditions and to operate with IR Lights. If you have not already found out about IR response and wavelenght then have a look at our IR Cut Filter page. Removing the filter from the view of an IR sensitive camera at night allows the camera to give good quality pictures during darkness. Then you get good monochrome (black and white) pictures which can be improved by the use of IR lighting which is mostly invisible to the human eye.
However often people wonder what the picture from an IR sensitive camera would be like during the day time. Does the camera still see in colour and if so then why have a filter at all?
Well the reason is that if you dont filter out the IR spectrum during daylight then the whole colour spectrum is reproduced in the camera image. White light contains the whole light spectrum, but we humans dont normally see IR light. Thats why we use a camera which can see IR light to transpose it so we can see in darkness.
If we add the IR spectrum to our colour image the colour produced by the camera will be anything but true. Have a look at the examples below. This is the same camera with the IR cut filter switched in and then out during a day time image.
IR Cut Filter On - All the IR light is filtered from the image so you get a lovely true colour daytime picture.
IR Cut Filter Off - The camera now thinks its night and shows its full IR range during daytime.
As you can see, if the IR sensitive camera views an image during the day time its full spectral response means that the IR spectrum is added to the image and the colour is totally inaccurate.
So to get the best of both worlds when using a true IR sensitive camera we switch in a filter during the day and switch it out during very low light.
There are other systems for limiting IR response electronically and they are becoming more efficient all the time, but there is still no substitute for actually filtering out the light you dont want, at the source, and then allowing it back in to the camera when you do want it.
For more information see:- Mechanical IR Cut Filters - Infra Red Wavelengths - Infra Red Lamp Range Information - Our Infra Red Lights.
Many of the live cameras in our live camera section are IR responsive so check them out too.