Unity Gain vs. Max Dynamic Range.

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tektonik
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Unity Gain vs. Max Dynamic Range.

Post by tektonik » Sat May 23, 2020 6:02 pm

Hi,

I watched Dr. Glover's YouTube presentation (several times actually, my learning process is primarily an osmotic one).

This inspired me to run the SC sensor analysis followed by the Smart Histogram. I noticed the SH gave me two options for analysis, Unity Gain (UG) and Max Dynamic Range (MDR).

I understand UG is one electron = one ADU, but don't understand why/how this is important to me, and especially since an MDR profile is available. It would seem (in light of my very nascent skills) that MDR would be the setting.

In other words, when would you not want MDR?

Also, UG. When would that be preferrable over MDR?

Thank you for your time.

Tektonik sends... P.S. Camera is ASI294C

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admin
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Re: Unity Gain vs. Max Dynamic Range.

Post by admin » Sat May 23, 2020 8:15 pm

Hi,

To be honest, after creating the smart histogram with the option of aiming for unity gain and after writing and presenting my talk, I've often asked myself the same question – is unity gain of any value at all?

My conclusion now is that there is no special value to using unity gain – the only time this might become interesting was if you had a camera where the read noise was less than one electron at this gain level. I'm not aware of any such camera existing (at least not in amateur astrophotography) and in any case even if the read noise was that small, the shot noise will almost always be much larger than one electron, meaning that recording the image at unity gain just so that one ADU is equal to one electron is largely a pointless exercise in recording noise at high fidelity.

By the way, if you haven't already found it, the missing part of my talk on choosing the right gain value is here - https://www.youtube.com/watch?v=ub1HjvlCJ5Y

Cheers, Robin

tektonik
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Re: Unity Gain vs. Max Dynamic Range.

Post by tektonik » Sat May 23, 2020 8:50 pm

Thanks Doc!

I did see the second presentation, but need and will watch again.

May I quote your response on our Astronomy Club forum?

https://www.rosecityastronomers.net/

Thanks Again
tektonik

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Re: Unity Gain vs. Max Dynamic Range.

Post by admin » Sun May 24, 2020 8:25 pm

Feel free, although remember is just my opinion :-)

Cheers, Robin

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