Quote:
Originally Posted by Stonius
Ah, it's logarithmic! - That makes sense!
The gains I've seen ppl using are 75, 139, 200 and 300.
As near as I can tell, gain 75 would correspond to an e/ADU of about 4.8, which means the entire 20,000 range of the wells are distributed across the 4096 possible ADU values.
Markus
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I use gain 100 because dividing the DN by 10 gives ~the electron count - easy for pixel peeping
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Re the well depth at gain, not sure what the architecture is, but apparently there is (variable?) gain at the pixel level. The effective well depth varies with the gain, presumably because the post-pixel internal data transfer mechanism/(or maybe ADC?) remains at 12 bits equivalent capacity.
eg, at gain 75, the "gain" (12 bits) is about 2 e/ADU, so, if the maximum transfer capacity is 12 bits equivalent, the maximum possible signal before saturation is 8192 electrons. The ZWO site lists a well depth of ~8000e at gain 75, so that theory works. This would imply that the linearity should be excellent for reasonably high gains, since the data will be truncated before the wells get anywhere near their physical capacity - seems to be the case.
cheers Ray