The A/D converter divides the electronic charges of the CCD pixels that are readout from the chip by a certain factor, the conversion factor, thus delivering a digital signal measured in counts (or grey levels). The maximum possible conversion factor would be the full-well capacity divided by the bit depth. However, often the conversion factor is somewhat lower than this. Some cameras provide the option to reduce the conversion factor for low light level experiments. (The manufacturers often refer to this as change of gain.) This way saturation is reached faster while the light-to-greyscale digitization is finer (fewer electrons per count) and the resulting intrascene dynamic range of the image improved.

An example: A 12 bit camera with a full-well capacity of 18,000 electrons might have a standard conversion factor of 4. That means, saturation (4095 counts) is reached with 16,380 electrons; this would be the effective full-well capacity. With a conversion factor of 2 the limit would be 8190 electrons, or half the signal. Consider an image with a background intensity of 1000 electrons and a maximum signal of 5000 electrons. With a conversion factor of 4 the resulting image would have an intensity spectrum of 1000 grey levels after background subtraction but 2000 if the factor is 2. The intrascene dynamic range would be twice as high.