Gain is a way of expressing how many electrons of charge are represented by each count (ADU). As long as the total well depth of a sensor can be represented, a lower gain is better to minimize the noise contribution from the electronics and give better resolution.
Readout noise is the number of electrons introduced per pixel into the signal upon the readout electronics of the device. One would like to have very low readout noise, in the range of 10 electrons per pixel per read or less, which is considerable higher than the CCDs.
date | quadrant | gain electrons per ADU |
readout noise electrons |
---|---|---|---|
October 2000 | down-left | 3.4 | 8.0 |
down-right | 3.4 | 8.5 | |
up-left | 3.4 | 7.8 | |
up-right | 3.5 | 9.2 |
We have a gain of 3.4 electrons per ADU and a readout noise of 8.4 electrons.
Theoretical measurements and the information in the header of the images, show a gain of 4.15 electrons per ADU and a readnoise of 25 electrons, which correspond to the data from the old detector and readout electronics.