Create an Infrared Photography Effect in GIMP

Simulating an infrared photography effect in GIMP transforms standard landscapes into surreal scenes by turning green foliage bright white or crimson while dramatically darkening skies and bodies of water. This visual transformation is achieved primarily through the Channel Mixer tool, where you redistribute and balance the color data between the red and green channels to mimic the way infrared light reflects off organic matter. By carefully re-weighting these channel values and enhancing the overall contrast, you can quickly produce both monochrome and faux-color infrared styles without expensive infrared camera filters.

Step 1: Select and Prepare the Base Image

Choose a landscape photograph that contains healthy green foliage and clear blue skies, as the high chlorophyll content in plants creates the most striking infrared contrast. Open your image in GIMP and right-click the base layer in the Layers panel, then select Duplicate Layer. Working on this duplicate preserves your original photo and allows you to adjust the effect's intensity later by changing layer opacity.

Step 2: Open the Channel Mixer

With the duplicated layer selected, navigate to the top menu and select Colors > Components > Channel Mixer (or use the GEGL filter Channel Mixer in modern GIMP versions). The Channel Mixer window displays controls for Red, Green, and Blue output channels, each containing sliders for their component color contributions.

Step 3: Re-weight the Red and Green Channels

Depending on whether you want a classic black-and-white infrared look or a false-color "Aerochrome" infrared look, apply the following channel calculations:

For Black-and-White Infrared:

  1. Check the Monochrome option in the Channel Mixer.
  2. Set the Green slider to +100% (or up to +150%). Because vegetation primarily stores its brightness data in the green channel, drastically increasing its weight forces trees and grass to turn bright white.
  3. Set the Red slider to balance the tonal range, typically between +20% and +50%, ensuring mid-tones maintain detail without clipping highlights.
  4. Set the Blue slider between -20% and -50%. A negative blue value deepens the blue sky and water into deep grays or pitch black, completing the traditional Wood effect.
  5. Click OK to apply the channel distribution.

For False-Color (Aerochrome) Infrared:

  1. Ensure the Monochrome option is unchecked.
  2. Select the Red Output Channel:
    • Set the Red input slider to 0%.
    • Set the Green input slider to +100%. This moves the green foliage data directly into the red spectrum, turning leaves vivid red or pink.
  3. Select the Green Output Channel:
    • Set the Green input slider to 0%.
    • Set the Red input slider to +100%.
  4. Leave the Blue Output Channel at its default settings (0% Red, 0% Green, 100% Blue).
  5. Click OK.

Step 4: Refine Contrast with Curves

Infrared images naturally feature extreme contrast. Go to Colors > Curves to fine-tune the dynamic range. Create a slight "S-curve" by dragging down the lower-left section of the line to crush shadows in the sky, and pulling up the upper-right section to make the foliage highlights pop.

Step 5: Add an Infrared Glow (Optional)

Classic infrared film is known for an ethereal bloom around bright areas. To recreate this:

  1. Duplicate your processed infrared layer.
  2. Go to Filters > Blur > Gaussian Blur and set the radius between 10 and 20 pixels depending on your image resolution.
  3. Change the blurred layer's mode to Screen or Overlay in the Layers panel.
  4. Lower the layer opacity to around 20%–30% to produce a soft, dreamy infrared halo.