Gain max from sensor analysis

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exaxe
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Gain max from sensor analysis

#1

Post by exaxe »

hello,
I test several cameras with the senor analysis function and I am a little blocked by the maximum gain that the software offers me.
It can't exceed 500 in gain value and my camera reaches 800. What interests me is having the full gain.
Is it possible to change this?
Thank you
Stephane
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Re: Gain max from sensor analysis

#2

Post by admin »

Hi Stephane,

not really - I am going to guess that you have a ZWO camera (or at least one that measures gain in the same way as ZWO), which means that gain=500 is ~300x brighter than gain=0, gain=800 would be 10000x brighter. Since the entire analysis process is done at a single light level, going up to maximum gain would require a range of exposures from ~1ms to 10s. There are issues with using exposures less than 1ms or more than 1-2s that can make the analysis unreliable (for some cameras, longer exposure are not exact, but rounded to the nearest 0.2s, for others, very short exposures give incorrect results). In order to avoid these problems and make the process as robust as possible, SharpCap tries to run the analysis with exposures between 1ms and 1s, and therefore limits the maximum gain range to about a factor of 300.

Having seen cameras from ZWO (and other manufacturers that use the same gain value arrangement) that do go beyond 500 gain, my experience has been that the noise level beyond 500 gain is so large as to make the camera pretty useless for serious imaging in that range.

cheers,

Robin
exaxe
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Re: Gain max from sensor analysis

#3

Post by exaxe »

no I have a player one, the uranus (imx 585).
The gain on this machine reaches 800.
It's aware that 800 is a lot, but I don't know if it's a relative or absolute value.
I'm testing.
after I capture on high gains (I regularly exceed 500 with the 290MM, as long as my software (Siril) manages to get a star or 3 stars, the rest (as long as the reading noise is low) appears.
At times it is necessary to go beyond serious imagery to go into lucky imagery.
thank you for your attention! and your software which is interesting!
I found a way to exceed 500 with the ISIS software.
thank you
Stephane
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Re: Gain max from sensor analysis

#4

Post by admin »

Hi,

thanks, I will look into this to see if the extension works (the P1 cameras seem to be well behaved in terms of varying exposure lengths, so it might be possible for them even if not for some other brands).

cheers,

Robin
exaxe
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Re: Gain max from sensor analysis

#5

Post by exaxe »

thank you!
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Re: Gain max from sensor analysis

#6

Post by admin »

I did extend the range, then did a test with the Mars-M... At 600 gain the FWD is 18 electrons! I decided it really wasn't worth the risk of going any further :) (At 600 gain, the gain range is 1000:1 - this still allows the analysis to be carried out between the low limit of 0.15ms and the high limit of 1s with a factor of about 6 available to allow for illumination brightness not needing to be spot on. Note that the low limit is about 15 times minimum exposure - you can't go down to minimum during the analysis, since at minimum exposure your options to change are to double the exposure - you do not have fine control over it).

cheers,

Robin
exaxe
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Re: Gain max from sensor analysis

#7

Post by exaxe »

thank you for taking an interest in my questions!
after it's true that 18th is not much (an understatement) but as we know, the dynamic rises with the number of raw units. But don't push anyway.
And at 18th the read noise is still stable or it goes up?
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Re: Gain max from sensor analysis

#8

Post by admin »

Hi,

the read noise starts to go up again - the minimum is at about 400-450 gain (note : 290 sensor)

cheers,

Robin
exaxe
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Re: Gain max from sensor analysis

#9

Post by exaxe »

thank you!
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