Which object is used to measure background or RTC in the example method?

• A. Crumbled aluminum foil
• B. A black cloth
• C. A glass beaker
• D. A sheet of white paper

Answer: (A)

The main idea here is using a simple, predictable reference target to gauge background radiation so you can calibrate the measurement. Crumbled aluminum foil provides a diffuse, near-Lambertian surface that reflects ambient infrared energy in a stable, reproducible way. Because the foil is crumpled, its reflections are scattered rather than mirror-like, which minimizes angle-dependent glare and yields a consistent background radiance for the camera to reference. This makes it a practical stand-in for measuring background or performing radiometric temperature correction (RTC) in the example method.

White paper or a black cloth would behave differently in reflectivity and emissivity, introducing more variation with viewing angle and lighting. A glass beaker can complicate readings due to transmission and its own spectral characteristics. The foil’s simplicity, availability, and reliable diffuse reflection make it the best choice for establishing a background reference in this context.