Undesirable fluctuations in image brightness are called?

• A. MTF
• B. Image Noise
• C. Quantization
• D. Scintillation

Answer: (B)

Desirable to notice is that the random, grainy variations in brightness you see across an image are called image noise. Noise shows up as speckled or patchy areas where pixel values wander around the true scene brightness, which lowers the signal-to-noise ratio and can hide fine details. It comes from the inherent randomness of photon arrival (especially when exposure is low) and from electronic noise in the imaging system.

MTF is about how well the system preserves detail at different spatial frequencies, i.e., sharpness, not random brightness fluctuations. Quantization refers to converting continuous gray levels into discrete steps, which can cause banding but isn’t about random brightness variation. Scintillation describes fluctuations in light output from the detector material itself, which can contribute to variability but the standard term for the general random brightness fluctuations across an image is image noise.