A thermal camera (microbolometer) detects infrared energy and converts it into an electronic signal, which is then processed to produce a thermal image, allowing us to perform temperature calculations.
Thermal cameras do not detect colour because the wavelength that they operate is beyond that of visible light. Instead, they create ‘false colour’ representations, in the form of images that can be interpreted. These Images are presented visually using colour palettes, to represent variations in temperature.
When conducting a thermal inspection or generating a report, there are many colour palettes that can be used to present your images.
The palette you choose is largely a matter of personal preference. Clearly, some palettes are better suited to particular applications. More often than not, a thermographer will have one or two good palettes of choice that they tend to stick to.
Linear Ironbow colour palette
High contrast colour palette
During an inspection my preference is to use a high contrast palette, to quickly observe small temperature variations. I then analyse my images in software and for reporting output i choose a palette that best presents my findings in a way i believe my client will understand.
A report can lose impact when the end user has to try and decipher which colour or shade corresponds to which temperature.
A very effective palette for presenting anomalies is the isotherm (or “Alarm”) palette, found on most modern cameras and software. The Isotherm can be used to highlight temperatures above, below or at an interval for any specific temperature value you input.
This is great for immediately drawing attention to a specific region in an image, and when presenting to the untrained eye, sometimes simplicity is key.
Isotherm “Above” and “interval” example
Isotherm “above” example image
There is no right and wrong to which palette we use, providing we highlight our faults in the most effective way possible.