Quantum Efficiency: The Sensor Spec Nobody Publishes
Almost every consumer camera you have ever bought came with a spec sheet, and that spec sheet left out the one number that most directly describes how good the sensor is at its actual job: catching light and turning it into signal. It told you the megapixel count, the ISO range, the frame rate, the buffer depth, the number of autofocus points. It did not tell you the sensor's quantum efficiency, and Canon, Nikon, Sony, Fujifilm, and the rest of the consumer camera business have quietly settled into never printing it.