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IMX342 CMOS v 16200 CCD

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#26 Stevan Klaas

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Posted 08 December 2018 - 06:07 PM

Got it. So practically at the macro scale of a bright star, the binning of the imx342 brings absolutely no advantage in terms of non saturation, since it would anyway saturate much more than 4 contiguous pixels. The possible advantage being then only in the lower relative read noise in fainter areas, and resulting higher SNR.

 

This would be why only a KAF16200 with almost 100K e- FWC per pixel would allow longer exposures without bloating bright stars while getting faint nebula signal.

 

I’ll keep my asi183 smile.gif.

 

Very clear. Thank you,

Stevan

 

CCD, when doing charge-domain binning, is using a non-sensel, separate charge storage area (typically bucket transfer shift register) to get charges from different pixels accumulated.

In IMX342 case, these four (2x2) pixels' FD (charge storage capacitors) are then linked thus "equalized" (becomes the average of these 4.)

 

In the case of CCD charge-domain binning, if the accumulating charge storage well is large enough,  then indeed FWC_under_the_binning_condition will be 4 times of each pixel's FWC (** note not always implemented that way, but let's stay in that ideal case for now.)

Also note, each pixel's FWC will still have play here.  That is, if a pixel reached its FWC during the exposure time, it will not go higher independent of final accumulated, binnned FWC is going to be.

 

In the case of IMX342, as JamesCA had stated, if any of the pixel is already saturated during the exposure time, that pixel's charge will stay at 100% no matter what.

 

Hope I don't confuse you than what it meant to be.

(May be a long sentence would help: pixel FWC is still a limiting factor on FWC; in binning operation, CCD type may overflow because it's addition, while CMOS type is not because it's averaging.)

 


Edited by Stevan Klaas, 08 December 2018 - 06:18 PM.


#27 james7ca

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Posted 08 December 2018 - 08:25 PM

Well, I think the binning performance on the IMX342 is a win, but what really makes or breaks CMOS sensors is probably their amp glow and pattern noise and specs are probably going to tell you nothing about those two issues. Of course, every now and then something else about a particular CMOS sensor will cause issues, like the micro-lens artifacts on the Panasonic MN34230 as used in the ZWO ASI1600 and the QHY163.

 

In terms of pattern noise, as I noted earlier there is at least some suggestion that global shutters (as in Sony's IMX174) MAY produce greater amounts of pattern noise, but that's not really confirmed and we certainly  don't know if that will be true on the IMX342 (which does, however, have a global shutter). That said, global shutters do offer some benefits for lunar and solar imaging, but probably not for DSOs.


Edited by james7ca, Yesterday, 01:07 AM.

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