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Is Sony Really Alpha?

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#2051 mmalik

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Posted 30 December 2020 - 04:02 AM

IMX Sharing may end here...

 

 

...as far 9um is concerned?

 

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#2052 sharkmelley

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Posted 30 December 2020 - 04:04 AM

a7SIII Darks (Post-mod)...
 

DSC00009_2000-Post.ARW

DSC00010_3200-Post.ARW

I've done an analysis of DSC00009_2000-Post.ARW

 

Firstly here's the RawDigger histogram:

 

SonyA7S3_Histogram.png

 

There are no histogram gaps, so it appears there is no digital scaling of the raw data.  This is good news because it probably means no coloured concentric banding in severely underexposed images.

 

Here is my usual plot to detect raw data filtering (a.k.a. "star eater"):

 

SonyA7S3.png

 

The very strong diagonal line is a result of pixel values being capped to the maximum value of their same colour neighbours, 8 neighbours in the case of red and blue or 12 neighbours in the case of green.  This is the same algorithm that Sony started to use on version 2 of their full frame mirrorless cameras.  The main effect is to bias the colour of small sharply focused stars toward green.  It's less destructive than the algorithm used on version 1 of the cameras.

 

As usual there is a small percentage of pixels that "escape" being capped - these are the ones appearing above the diagonal line.  What is unusual here is that they are mainly blue.  So I plotted the positions of these blue exceptions to the "rule":

 

SonyA7S3_BlueExceptions.png

 

It's odd that the blue exceptions to the rule tend to line up in distinct rows.  I've no idea why that should be.

 

Mark


Edited by sharkmelley, 30 December 2020 - 04:11 AM.

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#2053 MDieterich

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Posted 30 December 2020 - 02:57 PM

As a Nikon and previous Canon shooter I can say that from what I have seen Sony is king when it comes to low light sensors, case and point with their new A7siii. I was able to shoot with it a few weeks ago under dark skies near McDonald Observatory and with a mosaic of 35 panels using 30 second photos here is the result. Pretty insane how much HA this camera recorded and it is unmodified! Definitely excited to pickup one of these cameras and set of Sony lens to work with in 2021.

 

50780442001_613d1f7284_b.jpg


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#2054 akulapanam

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Posted 30 December 2020 - 09:49 PM

Very impressive. I assume unmodified ?

#2055 AnakChan

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Posted 31 December 2020 - 03:33 AM

Yes he did mention unmodified. I'm rather surprised by how much Hα was captured by an unmodified camera. i've not been able to pull out that much Hα with my D810A and that's meant to be a Astro biased DSLR.



#2056 mmalik

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Posted 31 December 2020 - 04:04 AM

Reflectivity Test of sort (a7SIII)...

 

 

 

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  • PrePostCompare.jpg


#2057 mmalik

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Posted 05 January 2021 - 05:41 AM

New Toy arrived today; while MILC adaptation seems straightforward, some 'dedicated' & EFW adaptation questions/dilemmas remain. Regards

 

 

Note: Japanese packaging; box in a box in a box in a box... not to mention ton of packing peanuts (...not shown)

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Edited by mmalik, 05 January 2021 - 06:44 AM.


#2058 mmalik

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Posted 05 January 2021 - 05:43 AM

MILC Adaptation (FSQ-85EDX)...

 

 

Note: Solution remains untested as of this writing...

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  • IMX455_EFW6.jpg

Edited by mmalik, 05 January 2021 - 05:44 AM.


#2059 SandyHouTex

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Posted 05 January 2021 - 09:59 AM

New Toy arrived today; while MILC adaptation seems straightforward, some 'dedicated' & EFW adaptation questions/dilemmas remain. Regards

 

 

Note: Japanese packaging; box in a box in a box in a box... not to mention ton of packing peanuts (...not shown)

Congratulations on the new scope.


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#2060 Spina@astro

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Posted 07 January 2021 - 10:50 AM

Taking the read noise values from photonstophotos.net I did a simple comparison between 7S and 7SM3.

I am posting here the exercise hoping that can be useful for further speculations.

My take is that the real-life performance gain of the new model can be 0.7-1 stop considering:

- the user sets both cameras to exploit the HCG circuit

- lower read noise/full well ratio

- better Ha response (to be calculated)

- maybe sligthly lower sensor temperature (difficult to quantify)

At the same time though, the exposure time of the subs will increases by 1/3 stop to match the new ISO smart values.

Honestly I was expecting more from a 6.5 years jump to a BSI sensor.

 

Sony 7Ss DR comparison

 

Also I want to thank mmalik for the teardown. Btw did you take some picture before the mod or have we missed a chance to measure the Ha response gain of the stock 7SM3 with respect to the older model?


Edited by Spina@astro, 07 January 2021 - 06:46 PM.

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#2061 mmalik

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Posted 08 January 2021 - 02:56 AM

Honestly I was expecting more from a 6.5 years jump to a BSI sensor.

I think you are to use ISO 2000 (instead of 1600) for a7SIII as 2nd gain (HCG) step. Please see if you can re-do your analysis? Regards

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  • Capture.JPG

Edited by mmalik, 08 January 2021 - 04:10 AM.


#2062 mmalik

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Posted 08 January 2021 - 03:11 AM

...did you take some picture before the mod or have we missed a chance to measure the Ha response gain of the stock 7SM3 with respect to the older model?

I didn't, weather didn't permit this baseline; I'll submit my post-mod Ha response samples as weather permits. Regards


Edited by mmalik, 08 January 2021 - 04:09 AM.


#2063 Spina@astro

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Posted 08 January 2021 - 04:18 AM

I think you are to use ISO 2000 (instead of 1600) for a7SIII as 2nd gain (HCG) step. Please see if you can re-do the analysis? Regards

According to J.Claff the jump is at ISO1600. However, I am not completely sure of his data. The way he calculates the pDR is even more questionable. That's why I prefer doing such exercises by myself.
If you can point me to other sources or take your own data I will redo the analisys.
 
photonstophotos Read Noise [ADU] for 7SM3
 
I didn't, weather didn't permit this baseline; I'll submit my post-mod Ha response samples as weather permits. Regards

Well, I think such comparisons still require a controlled environment. Such as a reliable light source that shines through a Ha filter. You could have taken a photo before and after the mod and notice the difference in exposure in the R channel.

The same can be done with the old 7S possibly using the same equipment. It's not as accurate as a certified calibration but it should be sufficient for our purposes.


Edited by Spina@astro, 08 January 2021 - 05:50 AM.


#2064 sharkmelley

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Posted 08 January 2021 - 05:30 AM

 

According to J.Claff the jump is at ISO1600. However, I am not completely sure of his data. The way he calculates the pDR is even more questionable. That's why I prefer doing such exercises by myself.
If you can point me to other sources I will redo the exercise.

 

Bill Claff's PDR is very different to the usual DR calculation:

https://www.photonst...namic_Range.htm

 

Mark


Edited by sharkmelley, 08 January 2021 - 05:31 AM.


#2065 Spina@astro

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Posted 08 January 2021 - 06:14 AM

Yeah Mark...about that: it's not very an astrophotography thing to

- normalize the DR with respect to the pixel size since we try to match the sensor with the optics and the seeing anyway

- normalize the DR with respect to the sensor dimensions for the same reasons (I find his APS-C pDR normalization to be misleading)

- subtract the white level since that non-linearity helps protecting the stars from saturation (at least for who doesn't do photometry)

 

I am aware that Claff has developed a procedure to standardize the measurements he does (or others do for him) but that's not public I am afraid. While very useful for the community I always take his results with a grain of salt. And that's good because I had to learn how to do all of that myself (and still prone to learn from you all!).

 

Regards


Edited by Spina@astro, 08 January 2021 - 06:41 AM.


#2066 mmalik

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Posted 08 January 2021 - 08:58 AM

If you can point me to other sources or take your own data I will redo the analysis.

Here... is one.

 

 

My pre and post mod data here... and here..., respectively. Regards



#2067 Spina@astro

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Posted 08 January 2021 - 09:59 AM

mmalik, I will need a couple of bias frames for each ISO value you want to evaluate.

Not much can be done with only a handful of darks especially without any description of (thermal) boundary conditions.

 

Maybe you're familiar with the Pixinsight script called CCDParameters, here is what I would do if I had that camera:

https://www.lightvor...pixinsight.html

As a reference on the topic:

https://www.cloudyni...ur-camera-r1929



#2068 mmalik

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Posted 12 January 2021 - 07:58 PM

Base Prep (a7SIII)...

 

 

Trying thermal conduction pads instead of paste

 

 

EDIT: Reverting to thermal paste; pads bit thick for the space...

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  • DSC06889.JPG

Edited by mmalik, 13 January 2021 - 07:08 AM.


#2069 mmalik

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Posted 12 January 2021 - 08:09 PM

Base Prep (a7SIII)...

 

 

Note: Orientation of cooler matters when trying to negotiate the bottom protrusions (...or the battery door); also copper lining has to be thick enough to firmly mate the base with the cold-plate

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  • DSC06899+.JPG

Edited by mmalik, 13 January 2021 - 07:08 AM.


#2070 mmalik

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Posted 12 January 2021 - 08:18 PM

Cooler attached (a7SIII)...

 

 

Bottom protrusions don't come into play in the following orientation of the cooler; this orientation 'does' block the battery door. Battery can be charged inside the camera via USB (red arrow) while timer is simultaneously using Multi (yellow arrow) port.

 

 

Note: Flipped orientation of the cooler will 'not' block the battery door

Attached Thumbnails

  • DSC06904.JPG
  • DSC06653++.JPG

Edited by mmalik, 13 January 2021 - 07:07 AM.


#2071 mmalik

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Posted 12 January 2021 - 08:21 PM

Cooler profile (a7SIII)...

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Edited by mmalik, 13 January 2021 - 07:07 AM.


#2072 mmalik

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Posted 12 January 2021 - 08:47 PM

Initial (cooling) observations (a7SIII)...

 

 

Given built in (Sigma) heat dissipation path to the CMOS, cooler performance seems to be quite optimal. I am seeing less condensation and less cooling of the body around the base since heat is more directly being dissipated from the the core (CMOS).

 

 

Note: Profile shown is using both USB interfaces, one for timer and one for charging battery inside the camera; entire setup as shown is being powered by Explorer 1000.

Attached Thumbnails

  • DSC06941+.JPG
  • Exp1000.jpg

Edited by mmalik, 13 January 2021 - 07:06 AM.


#2073 mmalik

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Posted 12 January 2021 - 09:36 PM

Cooling Test Results (a7SIII)...

 

 

Note: 3min, ISO2000. 20 darks taken in sequence without cooling; then cooler turned ON and another 20 darks taken in sequence with cooling, without any gap in the entire sequence. #20 (DSC00030.ARW) and #40 (DSC00050.ARW) here... for your evaluation. EXIF battery temp is charted; test conducted at 29C room temp.

 

 

Click for visibility...

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  • Capture+.jpg

Edited by mmalik, 13 January 2021 - 07:06 AM.


#2074 mmalik

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Posted 12 January 2021 - 09:44 PM

#20 and #40 JPGs (a7SIII)... from the graph above...

 

 

Note: Zoomed at 200%

 

 

Click for visibility...

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  • Comparison.JPG

Edited by mmalik, 13 January 2021 - 06:27 PM.


#2075 mmalik

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Posted 13 January 2021 - 05:46 PM

If cooler were not running (a7SIII)...

 

 

Following is the typical crescendo if cooler were not running. Regards

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  • Capture2.JPG

Edited by mmalik, 14 January 2021 - 01:44 AM.



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