Did some tests because some of the other nos. being touted on CN and PI appear incorrect esp. the belief that gain at ISO 800 ~= 1.
ex1
https://pixinsight.com/forum/index.php?topic=11983.msg73621#msg73621ex2
https://www.cloudynights.com/topic/526808-canon-600d-testing-results/Sharing here so a few T3i users who might benefit.
ISO Gain e/ADU Read Noise DN Read Noise e- Saturation e- DR stops Max ADU
--- ---------- ----------------- ------------- -------------- ---------- ----------
100 2.07 6.8 14.1 24828 10.8 14043
200 1.07 7.1 7.6 14747 10.9 15831
400 0.54 8.6 4.6 7483 10.7 15831
800 0.28 11.7 3.2 3812 10.2 15831
1600 0.14 18.7 2.6 1941 9.5 15831
3200 0.07 33.1 2.4 1003 8.7 15832
Could have used PI's BasicCCDParameters script (and I did to confirm some values), but went through the testing process described by Craig Stark to develop a better understanding of the terminology and assumptions.
https://www.cloudynights.com/articles/cat/column/fishing-for-photons/signal-to-noise-part-3-measuring-your-camera-r1929Some notable observations:
- The Mean Bias signal at all ISOs is ~2048 DN
- Max ADU at saturation at all ISOs except ISO 100 is ~15831. At ISO 100 it is 14043. This means that of the 16383 DN (14 bit), only 15831 - 2048 = 13783 are actually used. Less at ISO 100
- Full Well capacity based on ISO 100 data is 24828 electrons
- Unity Gain is roughly at ISO 200.
- The results reinforce my decision to image at ISO 800. It roughly marks the start of the ISO less state of the camera (read noise DN roughly varies linearly with ISO above this). Any lower and the read noise is much higher. Any higher and I'm losing dynamic range and amplifying other noise without any benefit.
