Full Well Capacity

Full well capacity defines the amount an individual pixel can hold before saturating. Saturation must be avoided in high performance CCD imaging because it diminishes the quantitative nature of the CCD and produces image smearing due to a phenomenon known as blooming.

Full well is dependent upon the pixel size of the CCD, whether or not MPP mode is used, and the operating voltages used on the CCD. Larger full wells are found on large pixel devices such as the KAF1000 from Kodak. MPP mode reduces full well since a large gate potential is not applied to the CCD electrodes during integration. This has the intended effect of reducing dark current, but it can suffer the penalty of reduced full well. This trade-off should be considered when selecting a particular CCD for high performance imaging applications.

Photometrics provides a test report with every camera system listing the full well for that particular CCD. This value has been measured at the factory and the camera gain has been adjusted so that the full range of the ADC matches the single-pixel linear full well capacity of the CCD at 1x gain. Only the linear range of the full well capacity is used since this is where the CCD functions as a radiometric detector and produces quantitative results. For this reason, full well capacities reported for our cameras may be lower than those found in CCD manufacturers data sheets.


 Pixel Size (µm)

Typical Full Well
Kodak KAF1400

6.8 x 6.8

45,000 e-
EEV CCD37-10

15 x 15

165,000 e-
Kodak KAF1000

24 x 24

630,000 e-