Circular saw, thermogram footage. Thermography records the temperature of surfaces by detecting long-wavelength infrared radiation. The colours show variations in temperature. The scale runs from white (warmest), through yellow, orange, red and purple to blue (coldest). A colour-coded temperature scale is at right, ranging from 15 degrees Celsius (dark blue) to 70 degrees Celsius (white). In this footage, the frictional heat generated by the circular saw shows up as bright yellow.