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ISO, sub length and image processing time

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#1 radon199

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Posted 03 December 2021 - 02:28 PM

My previous camera had fairly terrible read noise ( 2.6e at ISO 1600 vs 4.9e at ISO 400 ) and I was just starting out so I bounced back and forth between ISO 800 and 1600.

My new camera has much better read noise ( 2.05e at ISO 1600 vs 2.4e at ISO 400 ) but so far I have been sticking to ISO 1600 where read noise plateaus.

 

At my usual bortle 5-6 imaging spot I get to 1/3 histogram at around 30 second exposures at 1600. This is fine but it means I have to take a lot of subs to get a couple hours of integration time, and it means my processing times are quite long and my data footprint is large as well.

I can image at 60 seconds at ISO 800, and this halves the number of subs, and therefore halves the processing time.

My question is, assuming equal quality subs at both 30 and 60 seconds, and a difference of only 0.170 electrons between ISO 800 and 1600. Is it worth it to stay at 1600 at the cost of doubling the processing time?



#2 rblackadar

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Posted 03 December 2021 - 03:10 PM

I'm fairly new at this, so there are big gaps in my understanding, but for what it's worth...

 

Taking half as many subs means half as many reads., so, wouldn't that be a win as long as the read noise increases by a factor less than sqrt(2)? There are other reasons you might want to keep exposures short, but if those don't apply to you, I'd say go for it.



#3 drd715

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Posted 04 December 2021 - 01:55 AM

You may get better dynamic range with the lower ISO, but other factors may come into play that complicate an exact answer. Try it and see.




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