View Single Post
Old 07-12-2019, 12:50 PM
The_bluester's Avatar
The_bluester (Paul)
Registered User

The_bluester is offline
Join Date: Feb 2011
Location: Kilmore, Australia
Posts: 2,376
And having spent some hours mowing for the fire season then some more researching, I am still at the same point.

In my view the 14 bit ADC imposes inherent limitations on the camera for this application, just as the 12 bit in the ASI1600 and similar cameras. Regardless of saying that dynamic range is expressed as a ratio, in this context of these you can relate it back to absolute numbers because they are what you use to determine the ratio. It eventually has to go back to real numbers or it is a measurement without a unit and a completely useless abstraction.

Back to my original question/discussion point. The 14 bit ADC is used to quantise the input signal. At just above unity gain the read noise is markedly reduced, that wins back dynamic range on paper as the ratio between the minimum signal that can be discriminated from the noise floor (the "grass" in RADAR terms, I was a RADAR tech) and the maximum that can be measured is back to approximately what it is at lowest gain, but the absolute maximum (Which matters) has been reduced by two stops, it is a quarter of what it was before, as is the maximum.

Assuming the same noise profile existed, would it or would it not be an advantage (And potentially a big step in dynamic range) if it had a 16 bit ADC and the measurement range did not go from approx 7 to 65K electrons at minimum gain to 1.7 to 16K at unity but 1.7 to 65K at unity instead? The dynamic range would potentially improve by another two stops around unity gain and THAT is what I am interested in the discussion of.

And again, I am not critiquing Sony, who designed the sensor for a very different application, nor ZWO (And others) for adapting it to use in an astro cam and have to take what Sony dish up and make the best of it, just what limitations apply to particular hardware and what improvement changes might make make.
Reply With Quote