Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Sony IMX183 mono test thread - ASI, QHY, etc.

  • Please log in to reply
997 replies to this topic

#51 akulapanam

akulapanam

    Mercury-Atlas

  • *****
  • Posts: 2515
  • Joined: 26 Aug 2012

Posted 28 November 2017 - 03:29 PM

Dark Signal

The Sony IMX183, like any other sensor, has dark signals that grow, in the absence of light, over time. There is an underlying dark current, like any sensor, and there are also glows. Whether they are true amplifier glow (unlikely, amplifiers are built into each pixel now, however there may be other heat-generating units on the sensor die), or due to heat or even other signal (IR?) generated by SoC (system on chip, the integration of all the necessary readout and image processing logic into a composite package paired directly with the sensor, something Sony does as a matter of course these days), I cannot say for sure. Regardless, the impact is the same, and the patterns and practices to manage it are the same as with any other camera that exhibits amp glow.

Dark Current

The true dark current for this sensor appears to be very low. The official rating is < 0.002e-/s @ -20C. With exposures up to 10 minutes long, I have had very few problems with dark current, the most notable exhibition of which is hot pixels. The hot pixel count of this sensor is very low, lower even than the Panasonic MN34230ALJ. In part, the MN34230ALJ also appears to have RTS (random telegraph signal) which leads to semi-hot pixels, pixels that appear hot but only for a short time before returning to normal, which limits the effectiveness of dark frames for correcting hot pixels. Only true hot pixels will be corrected by a dark, and in these terms the MN34230ALJ seems to dark current almost as low as the IMX183, at around -0.006e-/s @ -20C.

As temperatures rise, the IMX183 has better dark current characteristics than the MN34230ALJ. Where the MN34230ALJ seems to double fairly quickly, around every 4.5C or around there, the IMX183 seems to double closer to every 10C. Even as hot as 25C, dark current on the IMX183 is only 0.06e-/s, which is actually incredible. This is an area where Sony seems to do significantly better than anyone, managing dark current.

Amp Glow

Given that dark current is basically a non-issue with the IMX183, that means the main dark signal concern is amp glow. The glows on this sensor are definitely time-dependent, they grow brighter with longer exposures. The general characteristic of the glows seems to be about the same as with any other Sony CMOS sensor, which all (based on my testing of IMX178, IMX174, IMX294, and IMX183 sensors) seem to exhibit the same general pattern: A primary starburst from the right edge of the frame, two tighter radial glows to the lower left and right corners, and a very faint glow to the upper left corner. Under very deep integrations, some slight glow along the top and bottom edges, and a very faint bubble about half the height of the sensor at the middle left edge.

Below is a worst case example of the glows (1 hour of 900s dark frames), stretched to an extreme so that the full characteristic of the glow can be seen:

SG6n5SE.jpg

I say the above is a worst case scenario, because it really is. The strange thing about the amp glows here is they seem to grow faster with longer exposures. I tested this by integrating the same total integrated dark frame time, 1 hour, using a range of different exposures at unity (gain 111). Comparing 60x60s, 30x120s, 20x180s, 15x240s, 12x300s, 8x450s, 6x600s and 4x900s, a clear pattern emerges:

1tfiBLp.jpg

I am honestly not sure how to account for this, however it does indicate that stacking more shorter subs will result in less total amp glow than stacking fewer long subs. This lends itself better to LRGB imaging than NB imaging, as well as imaging at shorter focal lengths rather than long. LRGB galaxy imaging at 800mm should be quite ideal, with subs in the 2-3 minute range. That said, I have found that 10 minute narrow band subs at gain 53 seem to fair ok with amp glow, and the sky signal buries the glows enough that there is no readily observable increase in noise from them. This may warrant further testing of the glow growth rate at other gain settings to see if the behavior differs with gain.

In the area of amp glow aesthetics (:lol:), the Panasonic MN34230ALJ is the clear winner. ;) It's glows are far less intrusive, fainter, and don't seem to grow quite as much or the same way as the Sony glows do. If you are chasing faint details with narrow band, I think the MN34230ALJ based cameras like the QHY163 or ASI1600 are better options.


That looks a lot like the ASI 178. Before you reach that conclusion on the 1600 we need to see the QHY because my QHY178 cool amp glow is virtually nonexistent whereas the ASI has tons like the image above. The difference is the anti amp glow circuit which ZWO doesn’t have...

#52 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23061
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 28 November 2017 - 03:54 PM

I don't believe that QHY is doing anything particularly special. I think they have just characterized the glow and are subtracting it out (although I could be mistaken here). I don't think they have any way to actually prevent it in the first place, since the source is on the image sensor itself. Thing is, even though the glow signal may be removed, the noise from that signal couldn't be. I would need to see more data to be sure, but I honestly don't expect there to be any SNR difference in the glow areas with the QHY vs. ASI. I would bet the SNRs are the same, even if the QHY doesn't exhibit the glow signal itself. The  glow is intrinsic to the sensor, unlike CCDs there isn't any external way to manage it such as placing heat generating or IR emitting devices farther away from the sensor, shielding the sensor from IR, etc.

 

I actually found the right term to search...QHY calls it anti-amplight. It sounds like they are actually using a control pin on the sensors to disable part of the circuitry of the sensor. They don't go into much detail, other than mentioning they are controlling it via the FPGA. I would need to see data to see how it affects SNR... If they are indeed actually disabling the SOURCE of the glow, then that could be quite significant. However, if it is done via the sensor pin interface, then it sounds like it is a function actually supported by the sensors, in which case, disabling that circuitry should be a matter of normal course for all implementations. Any manufacturer should be able to do the same thing...


Edited by Jon Rista, 28 November 2017 - 04:34 PM.


#53 Pauls72

Pauls72

    Vanguard

  • *****
  • Posts: 2378
  • Joined: 28 Oct 2007
  • Loc: LaPorte, IN USA

Posted 28 November 2017 - 04:18 PM

Yes that was a single bias. Here is a master bias of 100 stacked that I stretched the bajeezus out of. Yup, there is some banding. I uploaded both the master bias stretched and unstretched to the same place.

 

 

Master_Bias_000c-15C_11g_35o_100-MaxStreached2s.jpg



#54 CrzHrs

CrzHrs

    Ranger 4

  • -----
  • Posts: 394
  • Joined: 24 Jan 2014
  • Loc: Venezia (VE)

Posted 28 November 2017 - 04:38 PM

Since all cmos are SoC type, datapath is the same for all brands.amp glow is generated anyhow, As far as i know there is no magic hardware that can do something.

 

it is like you're buying an android with some customizations. Or, if you like more, it is like to have an ed doublet with a carbon tube plus feather touch :)

 

thanks jon for the deep test on this chip, it is a pleasure to read :)


  • Pug likes this

#55 Pauls72

Pauls72

    Vanguard

  • *****
  • Posts: 2378
  • Joined: 28 Oct 2007
  • Loc: LaPorte, IN USA

Posted 28 November 2017 - 04:59 PM

This is a QHY183C 6x600sec darks stacked.

 

 

QHY183C_MasterDark6x600s.jpg

 

 

 

This is the same image with a whole lot of stretch applied.

 

 

QHY183C_MasterDark6x600_Stretcheds.jpg

 

 

 

I have some master darks taken with the earlier drivers and there is more amp glow present.


  • Pug likes this

#56 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23061
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 28 November 2017 - 05:09 PM

Stretch it more! tongue2.gif Lots more. That's a tiny amount of stretch, at least compared to the data I've shared. Stretch it as much as I've stretched mine, so that the mean background levels and peak amp glow levels are at least similar and the contrast is similar, and then I think you will see much more of the amp glow. I can do the same thing with a low contrast stretch:

 

Z1fWIGV.jpg

 

I think part of the discrepancies here is not everyone stretches the same. Most of the QHY official examples of anti-amplight are barely stretched (and a lot of their images seem to have heavy black clipping as well), so it's tough to see any real difference. I use PixInsight's STF usually, and even if I do not my stretches are enough that you can fully see the full characteristic of the frame. When you don't stretch enough for the image to appear as anything other than "nearly black", you haven't stretched enough. It is easy to stretch narrow band data significantly, so it isn't like stretching this much is just a thing we do with darks.


Edited by Jon Rista, 28 November 2017 - 05:14 PM.


#57 Pauls72

Pauls72

    Vanguard

  • *****
  • Posts: 2378
  • Joined: 28 Oct 2007
  • Loc: LaPorte, IN USA

Posted 28 November 2017 - 06:57 PM

Is this stretched enough for you? Sorry, I don't have PI yet, it's on my wish list. So I have to use Nebulosity, StarTools or PhotoShop.

 

 

QHY183C_MasterDark6x600_MaxStretcheds.jpg


Edited by Pauls72, 28 November 2017 - 07:01 PM.


#58 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23061
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 28 November 2017 - 07:44 PM

Thanks. Looks like they did eliminate the corner glows. The starburst looks less intense as well. Pretty interesting. I wonder what it is exactly that they are turning off with that FPGA interface.


Edited by Jon Rista, 28 November 2017 - 07:45 PM.


#59 andysea

andysea

    Gemini

  • *****
  • Posts: 3429
  • Joined: 03 Sep 2010
  • Loc: Seattle, WA

Posted 28 November 2017 - 07:58 PM

I'm curious to see what effect the glow has in real life. I understand that the noise will be higher in the glow areas but I wonder if it is noticeable..

It will be interesting to see a finished image from this camera.

I have just ordered the ASI294, it has a different sensor but similar amp glow.



#60 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23061
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 28 November 2017 - 08:07 PM

I'll share some data soon here. You guys can evaluate for yourselves how much the glows matter.

 

With 10 minute subs, I can see the glow before calibration, but I have not been able to observe any increase to visible noise. I am only swamping read noise by 3-5x, which is decent but not great.

 

In the first post, I shared an example calibrated dark crop of the starburst glow area. The glow itself was removed, but it did leave some additional noise behind. You can take a look at that as well, see what you think.



#61 andysea

andysea

    Gemini

  • *****
  • Posts: 3429
  • Joined: 03 Sep 2010
  • Loc: Seattle, WA

Posted 28 November 2017 - 08:38 PM

Ah that's right I forgot that you were doing NB. I was thinking about broadband imaging. Theoretically with LRGB we should be able to easily swamp the read noise by a lot more than 3-5x.

I can't really see any additional noise in the crop that you posted but I'm currently looking at it on my calibrated screen. I'll check it out on a different machine where I can crank up the brightness.



#62 akulapanam

akulapanam

    Mercury-Atlas

  • *****
  • Posts: 2515
  • Joined: 26 Aug 2012

Posted 28 November 2017 - 11:37 PM

Thanks. Looks like they did eliminate the corner glows. The starburst looks less intense as well. Pretty interesting. I wonder what it is exactly that they are turning off with that FPGA interface.


Starlight Xpress also demoed a 174 based camera (and has a couple other chips in the works) that was as good as, if not better than, QHY in this regard. They said they approached Sony about making a change to fix this issue on all chips but Sony wasn’t interested.

#63 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23061
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 28 November 2017 - 11:41 PM

 

Thanks. Looks like they did eliminate the corner glows. The starburst looks less intense as well. Pretty interesting. I wonder what it is exactly that they are turning off with that FPGA interface.


Starlight Xpress also demoed a 174 based camera (and has a couple other chips in the works) that was as good as, if not better than, QHY in this regard. They said they approached Sony about making a change to fix this issue on all chips but Sony wasn’t interested.

 

Bummer. If it is fixable, strange that Sony won't bother to do it for every sensor. A lot of these sensors are for low light video security, and you would think eliminating amp glow there would be just as useful.



#64 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23061
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 29 November 2017 - 04:52 AM

Quick example of amp glow in a practical scenario. A 10 minute Gain 53 sub on Tadpoles, -20C setpoint, before calibration:

 

yofcyYq.jpg

 

And after calibration:

 

Bxyjebo.jpg

 

A 100% scale crop of the right-side starburst region to demonstrate the impact of the amp glow to noise (none, that I can see):

 

7hKKZjK.jpg


  • Pug and Cancington42 like this

#65 CrzHrs

CrzHrs

    Ranger 4

  • -----
  • Posts: 394
  • Joined: 24 Jan 2014
  • Loc: Venezia (VE)

Posted 29 November 2017 - 05:41 AM

Sorry but security doesn't go under 15fps usually. We're not really even close to amp glow territory. And of course, redesign chipset means re-do the project from zero, and maybe modify some printing machines

 

 

 

 

Thanks. Looks like they did eliminate the corner glows. The starburst looks less intense as well. Pretty interesting. I wonder what it is exactly that they are turning off with that FPGA interface.


Starlight Xpress also demoed a 174 based camera (and has a couple other chips in the works) that was as good as, if not better than, QHY in this regard. They said they approached Sony about making a change to fix this issue on all chips but Sony wasn’t interested.

 

Bummer. If it is fixable, strange that Sony won't bother to do it for every sensor. A lot of these sensors are for low light video security, and you would think eliminating amp glow there would be just as useful.

 



#66 QHYCCD

QHYCCD

    Vostok 1

  • -----
  • Vendors
  • Posts: 162
  • Joined: 06 Aug 2014

Posted 29 November 2017 - 06:04 AM

Our QHY183M is on the way, Just waiting the batch of the sensor coming. The sensor has a little delay to Dec.  QHY183M should have some amplifier glow control. Which can be seen in QHY183C images.

 

 

Best regards,

Qiu Hongyun


  • Miguelo, CrzHrs and gundark like this

#67 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23061
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 29 November 2017 - 08:29 AM

Sorry but security doesn't go under 15fps usually. We're not really even close to amp glow territory. And of course, redesign chipset means re-do the project from zero, and maybe modify some printing machines


True, however these cameras usually have two primary readout modes as well, driver controlled vs. camera controlled. When in camera controlled mode, amp glow often shows up with only a fraction of a second exposure. Perhaps the Sony IMX183 with a DDR buffer is different, I haven't actually done all that much testing with sub-second exposures yet.

#68 CrzHrs

CrzHrs

    Ranger 4

  • -----
  • Posts: 394
  • Joined: 24 Jan 2014
  • Loc: Venezia (VE)

Posted 29 November 2017 - 08:54 AM

That is something that never happened on any camera i used, as soon as i meet some engeneer i ask how do they manage this. i am courious :)



#69 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23061
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 29 November 2017 - 03:54 PM

Our QHY183M is on the way, Just waiting the batch of the sensor coming. The sensor has a little delay to Dec.  QHY183M should have some amplifier glow control. Which can be seen in QHY183C images.

 

 

Best regards,

Qiu Hongyun

Good to hear! Any chance you guys have some sample dark frames for the QHY183M? I'm very interested now in seeing what you guys are able to do with the amp glow. 


  • bobzeq25 and Stamos like this

#70 Stamos

Stamos

    Vostok 1

  • -----
  • Posts: 145
  • Joined: 30 Oct 2015
  • Loc: Athens, Greece

Posted 30 November 2017 - 07:25 AM

 

Our QHY183M is on the way, Just waiting the batch of the sensor coming. The sensor has a little delay to Dec.  QHY183M should have some amplifier glow control. Which can be seen in QHY183C images.

 

 

Best regards,

Qiu Hongyun

Good to hear! Any chance you guys have some sample dark frames for the QHY183M? I'm very interested now in seeing what you guys are able to do with the amp glow. 

 

Well, that would be very, very interesting...



#71 QHYCCD

QHYCCD

    Vostok 1

  • -----
  • Vendors
  • Posts: 162
  • Joined: 06 Aug 2014

Posted 30 November 2017 - 12:05 PM

 

 

Our QHY183M is on the way, Just waiting the batch of the sensor coming. The sensor has a little delay to Dec.  QHY183M should have some amplifier glow control. Which can be seen in QHY183C images.

 

 

Best regards,

Qiu Hongyun

Good to hear! Any chance you guys have some sample dark frames for the QHY183M? I'm very interested now in seeing what you guys are able to do with the amp glow. 

 

Well, that would be very, very interesting...

 

Just look at the dark frame of QHY183C. Only glow of on middle of right side still exist. But all the corner/ top/ down glow is completely removed by our technology. 


  • akulapanam, Jon Rista and DSO_Viewer like this

#72 suvowner

suvowner

    Ranger 4

  • *****
  • Posts: 318
  • Joined: 22 May 2016
  • Loc: Arkansas

Posted 01 December 2017 - 09:52 PM

so for a celestron 8" edge with hyperstar F2.1/425mm the 183 seems like it would work well, but with this scope I can also use focal reducer and shoot at F7/1422mm or F10/2032mm , at these longer focal lengths the 1600 would prob be the better choice, so do you think the better resolution at 425mm would justify the 183 over the 1600 ??

 

and what about the reflections of the sensor cover glass on the 1600, do you see the same problem with the 183 ?

 

thanks



#73 akulapanam

akulapanam

    Mercury-Atlas

  • *****
  • Posts: 2515
  • Joined: 26 Aug 2012

Posted 01 December 2017 - 10:45 PM

so for a celestron 8" edge with hyperstar F2.1/425mm the 183 seems like it would work well, but with this scope I can also use focal reducer and shoot at F7/1422mm or F10/2032mm , at these longer focal lengths the 1600 would prob be the better choice, so do you think the better resolution at 425mm would justify the 183 over the 1600 ??

 

and what about the reflections of the sensor cover glass on the 1600, do you see the same problem with the 183 ?

 

thanks

The best use of this camera will be with scopes with lots of Dawes resolution but short focal lengths so hyperstar, RASA, RH200, and Tak 180 would all be great with this one.



#74 Jon Rista

Jon Rista

    ISS

  • *****
  • topic starter
  • Posts: 23061
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 02 December 2017 - 11:05 AM

so for a celestron 8" edge with hyperstar F2.1/425mm the 183 seems like it would work well, but with this scope I can also use focal reducer and shoot at F7/1422mm or F10/2032mm , at these longer focal lengths the 1600 would prob be the better choice, so do you think the better resolution at 425mm would justify the 183 over the 1600 ??

 

and what about the reflections of the sensor cover glass on the 1600, do you see the same problem with the 183 ?

 

thanks

I don't really think either camera would really be all that great at f/10...however, either should be ok at f/7, with the ASI1600 having the benefit of a larger FoV. 

 

As for microlens diffraction. With VERY bright stars, I have seen a rather interesting diffraction artifact (I need to get some test data to show it), but I haven't seen the same kind of microlens reflections as with the ASI1600. I don't know exactly what causes the issue in the ASI1600, so I don't know whats different about the ASI183, but if you encounter any sensor diffraction with the 183 it's a more pleasing effect.



#75 suvowner

suvowner

    Ranger 4

  • *****
  • Posts: 318
  • Joined: 22 May 2016
  • Loc: Arkansas

Posted 02 December 2017 - 12:10 PM

 

so for a celestron 8" edge with hyperstar F2.1/425mm the 183 seems like it would work well, but with this scope I can also use focal reducer and shoot at F7/1422mm or F10/2032mm , at these longer focal lengths the 1600 would prob be the better choice, so do you think the better resolution at 425mm would justify the 183 over the 1600 ??

 

and what about the reflections of the sensor cover glass on the 1600, do you see the same problem with the 183 ?

 

thanks

I don't really think either camera would really be all that great at f/10...however, either should be ok at f/7, with the ASI1600 having the benefit of a larger FoV. 

 

As for microlens diffraction. With VERY bright stars, I have seen a rather interesting diffraction artifact (I need to get some test data to show it), but I haven't seen the same kind of microlens reflections as with the ASI1600. I don't know exactly what causes the issue in the ASI1600, so I don't know whats different about the ASI183, but if you encounter any sensor diffraction with the 183 it's a more pleasing effect.

 

from what I have read the cover glass over the 1600 sensor is not ar coated, per Sam this is how the sensor is made so zwo can't do anything about it......was just curious if the sony sensor had ar coated cover glass or not and might have not have that same problem.....

 

https://zwoug.org/vi...bbb86912ad3fe25

 

I am far more likely to image at f7 or f2.1 , makes me lean towards the 183, with the smaller pixels it might allow me to image a few midsize targets at f2/1 rather than f/7 , since the higher resolution would allow me to crop a bit more of the image, and imaging at f/2.1 is soooo much easier....

 

thanks for your reply


Edited by suvowner, 02 December 2017 - 12:18 PM.

  • Pug likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics