This distortion is present when picture or sync pulse luminance amplitude is affected by APL changes. This is different from APL induced Transient Gain Distortions which only occur at the APL change transition time. Rather, this distortion refers to gain changes that occur after the APL has changed. The amount of distortion is usually expressed as a percent of the amplitude at 50% APL, although sometimes the overall variation in IRE units is quoted. This is an out-of-service test.

This distortion causes picture brightness to seem incorrect or inconsistent as the scene changes.