Using a Standard Single-Sensor Camera for Pseudo False Color Infrared Digital Imagery
Because all three color dyes in a matrix-filtered sensor pass the near infrared wavelengths equally, most natural color cameras use an IR cut-off filter to restrict image data to the RGB color range. Some digital aerial photography companies have removed the IR cut-off filter from their sensor and replaced it with a yellow filter to block blue light. They then juggle the colors applied to each band so that the original blue band prints red, the original red band prints green, and the original green band prints blue.
This effect mimics the appearance of the False Color Infrared Aerial Film still produced by Kodak, since the original blue layer is now being exposed mostly in the near infrared range.
However, these images do not have the same spectral distinction as the film because the other two bands in the digital image are also absorbing equal amounts of infrared radiation. (In the film base, the color absorbing bands are layered with Blue on top, so IR radiation is still blocked from the Red and Green sensitive sections. On the digital sensor, they sit beside each other.) The results can be corrected somewhat by partly subtracting the blue band from the red and green bands, but the quality of the red and green bands is degraded and the results still have little radiometric significance.
This process has limited value for aerial interpretation or classification. It should not be confused with true digital multispectral imagery that has distinct spectral bands from separate sensors and can be calibrated for radiometric analysis.
Pseudo false color infrared image from a Redlake ES11000 single-sensor digital camera. We experimented with this imagery, but do not recommend its use.