How does night vision in camcorders work?

Factual Questions
1

Does it like, create light that is only visible to the camera lense but is invisible to us?

2

Near infra-red isn’t visible to the human eye. Many CCDs are sensitive to it and can therefore take pictures in what we piercieve as darkness. In fact many digicams have a filter so that IR will not get to the imaging device. The original Minolta Dimage 7 camera is sought because it doesn’t have such a filter and does pretty good IR work. One can illuminate with a light that has an IR pass filter so that no visible light - to humans - lights the subject.

3

How night vision works
Same idea, but integrated into a camcorder.

4

Why are such filters installed then? You imply that a camera without it is very popular, so why do the companies not make more like it?

5
      • Yea, basically. CCD chips (that digital and videocameras use) are normally sensitive to IR light somewhat beyond the human range of vision. “Photographic” cameras usually have an internal IR-suppressing filter to help balance out the visual effect of IR, because the intent of these cameras is to capture the image the same way you see it–and without the IR filter in place, the image the camera sees might be lighter/“whiter” than what you’d see. Any video or digital camera will do this, even cheap webcams will. It’s nothing special, and has been known since the earliest CCD’s were used. It is more difficult to get an unfiltered CCD to ignore IR light than it is to get them to pick it up. You can usually “see” the IR LED of a typical remote-control blink if you view it with a digital camera or videocamera while you press the remote-control’s buttons.
  • “Photographic” electronic cameras tend to have a fixed internal IR filter, but security cameras–especially those intended for low-light use–usually don’t. They just have a circuit that automatically adjusts the white balance to “about” where you set it. The notorious Sony Nightshot cameras had an internal IR filter (for normal/daytime use) that flipped out of the way of the image when you wanted.
  • You can now buy “night vision” cameras specifically for night-observation use. It is generally held that the CCD cameras are a bit less brighter than the generation-1 tube scopes, but the CCD cameras are clearer and have better image contrast. Another important aspect (very handy for police and security work) is that these cameras usually produce a video signal and have a video-out jack, so their image signal can be recorded.
  • The light amplification is really not that great. Most police and military do not bother with trying to use gen-1 NV equipment anymore at all. A generation-1 NV scope amplifies light 900-1000 times and costs $100+, a gen-2 goes 25,000 times and costs maybe $1200+ a gen-3 goes 35,000 times and costs $2000+. When you see cool war or police footage on TV done at night, --you know, the videos where it’s totally dark but everything is plainly visible, just shaded green-- they are using a gen-2 or -3 night-vision scope.
    …
  • Some examples I found shopping for digital night vision (often abbreviated now as “DNV”):
  1. the Nitemax was the first CCD direct-use camera I saw specifically intended for night use, it’s been around for a couple years now: http://www.opticsplanet.net/nitemax.html
  2. the Bushnell Nighthawk is a newer one, same principle: http://www.opticsplanet.net/bushnell-dnv-night-hawk-night-vision-viewer-260900.html
  3. Here is one example of a security camera that has low-light capability–notice how expensive it isn’t: http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=47546
    -it says the minimum light required is “0 lux” because it probably has an IR LED on it to provide light when there isn’t enough ambient light available.
    ~
6 
 Can you please explain this? Does it have something to do with "x-ray vision"?  :cool:
7
      • No “x-rays” involved, just 1920’s style death rays.
        ~
8

I wouldn’t say it’s extremely popular, kind of a specialized field. AFAIK the IR filter is so that images only get light visible to us so images are more predictable. Most times it doesn’t make a huge difference I can see.

9

Sort of. On most cameras, the IR blocking filter is fixed in front of the CCD. The SONY camcorder had a “nightshot” feature which was essentially a removable IR blocking filter. When you turn on this feature the IR blocking filter moves out of the light path, allowing high sensitivity even in the dark. If you add a IR-passing filter (passes IR and blocks visible light) to this camera, you have a very good IR-only camera.

The problem is that some fabrics are more transparent in the IR than in visible light. The SONY nightshot camera with an added IR-pass filter can see right through some types of clothing, e.g. swimsuits made of thin synthetic fabric. I’m sure you can find examples on the net if you are really curious.

10

And I just happen to have a SONY camera with nightshot… :wink:

11

Hey! Don’t accuse me of such nonsense!!! looks around nervously