Which term best describes a blotchy appearance caused by an insufficient number of photons reaching the image receptor?

• A. Quantum mottle
• B. Ambient noise
• C. Quantum noise
• D. Photon starvation

Answer: (A)

When there aren’t enough photons reaching the image receptor, the photons that do arrive arrive by chance in uneven amounts across different image areas. Those random fluctuations become visible as a blotchy, mottled texture on the image. This visible mottling is described as quantum mottle. It reflects the shot-noise inherent in low photon counts, which is why the image looks grainy or blotchy.

Ambient noise is unrelated to photon flux and comes from environment or electronics. Quantum noise is the underlying statistical fluctuation in photon arrival, but the term that specifically describes the blotchy appearance is quantum mottle. Photon starvation can describe severe underexposure, but the characteristic blotchy pattern tied to low photon counts is best captured by quantum mottle.