By Quantum efficiency in CMOS sensors measures how effectively each pixel converts incoming photons into electrons that become your image signal. Expressed as a percentage, it tells you what fraction of the light hitting your sensor actually contributes to the photograph. A sensor with 60% quantum efficiency captures six out of every ten photons as usable data, while the remaining four are lost to heat, reflection, or simply pass through without detection.
This specification directly impacts three things every photographer cares about: how clean your images look in dim conditions, how long your battery lasts during intensive shoots, …
