Sunday, April 21, 2002

Infrared Photography

Did you know you can shoot infrared photos with a digital camera? I dimly remebered having read about this somewhere (maybe over at 2020 Hindsight?), so I did a search at Google. Here are a few interesting sites:

2 thoughts on “Sunday, April 21, 2002

  1. Roberto

    Do you know if you will see the heat get out of the windows of a house if you take a photo at night?

  2. Andrea Frick

    First of all, it doesn’t have to be dark for infrared photography. You have to use a filter that blocks the visible light in order to capture the infrared light because it is so much weaker intensity-wise than the visible light. So it would make no difference if it’s dark or not.

    Infrared electromagnetic waves have wavelengths between approximately 100 000 nm and 770 nm. Visible light has a wavelength between 770 and 390 nm. Everything with a temperature above 0 K (-273.15°C or -459.67°F) emits electromagnetic waves in a range of wavelengths according to its temperature, where the temperature determins the wavelength at which the emission has the highest intensity.

    A house has a temperature of about 300 K (20°C or 68°F) and therefore emits electromagnetic waves around a wavelength of 15 000 nm, which isn’t anywhere near the range for visible light. Since digital cameras use microchips that are sensitive mainly to visible light and near infrared (the range of infrared nearest to visible light), I don’t think they could capture the heat from a house or a human. The house would need a temperature of 3 000 to 4 000 K (3 273 to 4 273°C or 5 923 to 7 723°F) in order to be visible for a normal digital camera.

    Some of the sites I linked say that you can test your camera using a remote control. Most remote controls use infrared light with a wavelenght of 950 nm, which is pretty close to the range of visible light; thus, a digital camera can capture it.

    If you look at the examples for infrared photography on the sites I linked, you can see that humans appear almost “normal” and don’t glow because of the heat they’re emitting. A house would appear “normal” in the same way (for example, see this photo, which has been taken using infrared sensitive film). You are probably thinking of images like this one though; they can’t be captured with normal digital cameras but require special equipment.

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