The first commercially available IR cameras weighed anywhere from 10 to 30 pounds and had to be cooled with liquid nitrogen or compressed argon gas.
Their modern counterparts are dramatically less expensive and easier to use.
In a gray-scale image, cooler surfaces appear dark, with lighter areas indicating greater warmth.
In the "rainbow" palette, the temperature scale is displayed in a full color spectrum.
The red-blue palette is a variant of the rainbow palette.
The amber image is similar to grayscale but based on shades of yellow.