eNews Exclusive: Infrared Videography (page 2)

Natural lighting from the sun is an excellent source of IR light. Even small amounts of sunlight entering a room can provide acceptable images. Shooting outdoors is usually not feasible, as the intense sunlight will completely blind and perhaps damage the CCD, unless you are shooting at twilight or under a heavy cloud cast. In any instance, it is advisable to employ an IR filter when using sunlight. A suitable filter, like the Hoya RM72 or Wratten 87 will block wavelengths shorter than 720 to 770 nanometers. There are longer wavelength filters like the Wratten 87A, but these are usually too restrictive, especially if employing infrared LEDs as backup illumination. In any case, if no infrared filter is readily available, a deep red filter like the Wratten 29 may be sufficient in most cases.

Fluorescent lights as IR sources are unpredictable, depending on the phosphor type, so it is best to avoid them. Incandescent lightning is also a very effective source of IR light, and it is amazing how small-wattage bulbs will provide perfectly adequate illumination. Some of the higher-powered infrared illuminators for surveillance use are actually highly-filtered incandescent lights, and no additional camera filter may be necessary.

Whether it is candlelight, a campfire or even a barbecue grill, fire (considered an almost useless light source for conventional photography for its orange-reddish cast) is nevertheless an excellent infrared source. Images appear harsh but omnidirectional, and the lighting effect is exactly what most people associate with night scenes. Figure 3 shows a typical night scene shot both in normal and infrared camera mode, with a few small candles as the only light sources. The detail in the color photograph is negligible, except in the very close vicinity of the candles. On the other hand, infrared light reveals most, if not all, of the foreground detail and some additional background detail.

One last word, which to some may be obvious: Do not focus on ambient light and then lock the focus and shoot with IR light. Depending on the wavelength and type of lens, the focus point may shift. Always focus with the light you are planning to shoot with. Some lenses have engravings showing the IR focus point if manual focus is desired.

The bottom line is that infrared videography will expand your shooting choices and moods, if employed wisely. It requires some experimentation, but this is part of the challenge. Happy movie making!

Fernando Garcia is an electronics engineer and photography enthusiast.

*WARNING: We are emphatically not recommending you do this.*

The CCD in your camcorder is already very sensitive to IR radiation, but an internal glass IR filter blocks most of this spectrum. Camcorders that have an IR night mode remove this filter when that shooting mode is engaged. Theoretically (did we already mention that we are not recommending you do this?), one could hack a camcorder and permanently remove this filter from in front of the CCD. A Google search will turn up plenty of amateur camcorder surgeons who have (more or less) successfully hacked their old and expendable camcorders.

Almost all camcorders have a low-light or night mode, but decoding what that means can be tricky. If a camera has a full-color night mode, it means that the shutter slows (usually to 1/4 second) to produce Max Headroom-type stuttery video. Look for camcorders with an explicit IR night mode if you want to shoot in complete darkness. Often, these cameras have an IR LED or two for illumination right on the camera body.

If your camcorder does not have an IR night mode and you really can't afford the risk of an IR filter hack, you could get an IR surveillance camera. These tiny devices shoot a relatively low-resolution image and the quality is not that great, but they come ready-made to illuminate in IR and output a video image via an RCA jack or S-video to your camcorder's video input jacks. This depends, of course, on whether your camcorder can record from analog sources.

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