The colors on a thermal image are not what the scene looks like. They are a code for temperature, and you can usually switch the code to suit the job. The underlying data does not change.
The common palettes
- White-hot: warm objects appear white, cool ones black. Looks like a familiar black-and-white image and is popular for scanning outdoors.
- Black-hot: the reverse. Some people find it easier to read detail this way.
- Ironbow (iron): a gradient from dark purple through red and orange to yellow and white. A favorite for general inspection because it shows smooth temperature steps.
- Rainbow: many distinct colors, which exaggerates small temperature differences. Good for spotting subtle changes, but can make normal variation look dramatic.
- Red-hot and other highlight modes: only the warmest areas are colored, which helps pick out hot spots against a plain background.
Choosing for the job
- Home energy checks and moisture: ironbow or rainbow to show gradients.
- Electrical and mechanical: ironbow or a highlight mode to isolate hot components.
- Outdoor observation: white-hot or black-hot for clear shapes.
Scale matters more than color
Many cameras auto-range, meaning the color scale stretches to fit the hottest and coldest things in view. That means the same color can represent different temperatures from one image to the next. For comparing images, lock the temperature span where your camera allows. Always read the temperature scale on screen rather than judging by color alone.
Reports
If you are documenting findings for a client, use one palette and one scale consistently so images are comparable. See what inspectors need in a thermal camera.
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