Infrared

The earth is illuminated with a broad spectrum of electromagnetic radiation (light) - ranging from gamma rays to radio waves - almost all of which is invisible to us. The tiny fraction of the light spectrum that our eyes can detect triggers electrical signals in the light-sensitive neurons in our eyes. Depending on the types and location of neurons stimulated, our brain creates images and what we perceive as “colors”. A digital camera works in a similar fashion, only software in the camera assigns colors to pixels in the image based on an algorithms that interprets electrical signals from the camera’s sensor.

Just beyond the red end of the human visible spectrum lies infrared light. Although some animals can see in the infrared, our eyes cannot. As a result, our brains lack the ability to create “colors” for infrared wavelengths. But by using a camera suitably modified to detect infrared light, and filters to block visible light from the sensor, it is possible to create photographs showing how the world looks in the infrared. Because our brains do not understand “colors” in the infrared, the images are in black and white. Many photographers use filters that allow some wavelengths of visible light to reach the sensor, or subsequently modify their infrared images by adding false colors to various image elements. These false color images can be artistically interesting, even beautiful, although they do not accurately reflect a true infrared image.