Quantum evaluation is the measurement of the percentage of photons of light converted to electrons and picked up by a pixel in a wavelength. The wavelength is expressed in nanometers (nm). For example for a wavelength of 650 nanometers (red), if the quantum efficiency is 60%, there will be 60% of the light photons which will be picked up by the camera sensor in the red light spectrum. The percentage varies depending on the wavelength.
Quantum efficiency is therefore an important element to consider in the evaluation of a camera.
CCD Camera Sensor Quantum Efficiency Rating Table
For deep sky photography, here is an example of evaluation to be performed in the visible light spectrum (for the human eye) ie for red, green and blue:
| Light spectrum | Wave length | Performance |
| (Nm) | quantum | |
| Infrared | 800 | n / A |
| Red | 650 | 60,00% |
| Green | 550 | 50,00% |
| Blue | 450 | 40,00% |
| Ultraviolet | 400 | n / A |
| Average quantum yield | 50,00% | |
Most CCD camera manufacturers provide the quantum efficiency of their cameras. In the summary specifications of their products, they indicate, most of the time, the best performance obtained for a wavelength. They also often provide the graph of quantum efficiency at all wavelengths. This graph is used to evaluate the average quantum efficiency of the camera. Here's a sample chart:
Average quantum efficiency: 51% (R49%, V58%, B45%)
Richard Beauregard
Sky Astro - CCD
Revised 2021/03/13