I have noticed that in the Camera Manual, Unity Gain is shown as 120 but in the Ascom driver settings dialog, under the Unity Gain pre-set, Gain is shown as 111.
Am I misunderstanding? Which is correct.?
Sorry for the problem.
To be honest, neither of these values is strictly accurate.
As we know, Unity gain means one value maps one eletronic. Consider noise and the limitations of test conditions. We can only approximate this value.
For 120, It is inferred from the curve which is fitted by a series of tested points.
For 111, it's a mathematical algorithm value from the tested point.
Usually, please use the 111, because the scale of the curve, when inferred, It's hard to get within 10. And, usually for easy of introduction, we will choose some of the easy-to-remember values on our manual.
Thanks for the reply.
Are you saying the 120 is the straight line interpolation but that the 111 comes from the actual formula? Does that mean the 270 gain setting for LRN in the Ascom driver is the correct value too?
For the gain, Only the unity gain is calculated.
For example, there is another camera.
when set gain=0, we can test the electronic gain is 1.5 e-/ADU, At this gain, we will get the largest full well capacity.
When we set the gain=60, we can test the electronic gain is 0.9 e-/ADU.
When we set the max analog gain=120, we will get the lowest read noise, at this point, the electronic gain is 0.2e-/ADU.
If we continue increase the gain, the camera will use the digital gain, the read noise and the electronic gain will not change, they just get amplified by the digital gain.
So LRN usually means the max analog gain is 120, it must be a correct value.
But for Unity gain. if we draw a curve with the data we tested, you will find the gain is around 50 when electronic gain is 1.0e-/ADU. But if you use the mathematical algorithm to calculate it, you may get 45 means electronic gain=1.0e-/ADU. But in the truth, maybe electronic gain equals 1.0e-/ADU when the gain is 46.5.
Please forget my poor drawing.