IR photography works by capturing infrared (IR) light rather than the visible light spectrum that traditional photography uses.
Traditional cameras are primarily designed to capture the light we see with our eyes. However, digital sensors and film can also be sensitive to other forms of electromagnetic radiation, including infrared light, which is beyond the red end of the visible spectrum.
Here's a breakdown of the process:
- Light Source: Like visible light photography, the scene must be illuminated. This can be from the sun (a strong source of IR) or artificial IR sources.
- Sensor Sensitivity: The image sensor (in digital cameras) or the film (in analog cameras) is capable of detecting both visible light and infrared light.
- Blocking Visible Light: To isolate the infrared spectrum, a crucial component is used: an infrared-passing filter. This filter is placed in front of the lens.
- Function: This specialized filter is designed to let infrared (IR) light pass through to the camera, but blocks all or most of the visible light spectrum.
- Appearance: Because they block visible light, these filters often appear black (opaque) or deep red to the human eye.
- Capturing the Image: With the visible light filtered out, only the infrared light reflecting off or emitted by the scene reaches the sensor or film.
- Processing: The camera or film records this infrared data. The resulting images often have a distinct look, with vegetation appearing bright white (due to strong IR reflection) and water or skies appearing dark (due to low IR reflection/transmission).
In essence, IR photography sees the world using light invisible to our eyes, primarily achieved by using a filter that blocks normal light while allowing infrared light to reach the sensor.
