Full Well Capacity and Dynamic Range in CCD Cameras
The dynamic range of a CCD is typically defined as the full-well capacity divided by the camera noise and relates to the ability of a camera to record simultaneously very low light signals alongside bright signals. The ratio is often expressed in decibels which is calculated as 20log (Full well capacity/read noise) or in the equivalent number of A/D units required to digitise the signal.
Pixel Size µm2
Full Well Capacity e-
Read Noise e-
iXon3 885 EMCCD EM Amplifier with No Gain (dynamic range higher with EM gain)
8 x 8
20 (x3 pre-amp)
Luca S EMCCD EM Amplifier with No Gain
10 x 10
iXon3 897 EMCCD Conventional Amplifier @ 1MHz (dynamic range higher with alternative pre-amp)
The table above shows the full-well capacity and dynamic range of a small selection of Andor cameras.
The full-well capacity is the largest charge a pixel can hold before saturation which results in degradation of the signal. When the charge in a pixel exceeds the saturation level, the charge starts to fill adjacent pixels, a process known as Blooming. The camera also starts to deviate from a linear response and hence compromises the quantitative performance of the camera. Larger pixels have lower spatial resolution but their greater well capacity offers higher dynamic range which can be important for some applications.