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Sony A7r5 no longer has Sony star eater

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#76 sharkmelley

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Posted 01 March 2024 - 06:42 PM

Continuing with the Sony A7CR, let's examine the potential issues of data scaling and the correction that causes the concentric colour polygons.

 

Firstly here is the RawDigger histogram of one of the flat files:

 

SonyA7CR_histogram.jpg

 

There are no spikes and no gaps!  This is excellent news because it means no data scaling is being applied that potentially causes concentric coloured rings.

 

Here are the plots of 3 flats with very different levels of exposure where the (bias-subtracted) red channel is divided by the (bias-subtracted) green channel and the (bias-subtracted) blue channel is divided by the (bias-subtracted) green channel:

 

SonyA7CR_NoPolygons.jpg

 

Lens corrections were switched off and lossless data compression was used. There are no hints of the usual coloured concentric polygons that plagued earlier Sony mirrorless cameras - even though the Sony FE 20mm F1.8G lens was recognised by the firmware and the lens correction parameters were written into the EXIF header.

 

So now we have 2 Sony mirrorless cameras that look excellent for deep-sky astrophotography - the Sony A7R5 and the A7CR. The ZV-E1 is also a possibility except that it does not have bulb mode so there's no possibility of doing exposures longer than 30sec.

 

Mark


Edited by sharkmelley, 02 March 2024 - 07:51 AM.


#77 whwang

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Posted 01 March 2024 - 07:59 PM

Hi Mark,

 

In the flat B/G images, there is a circle of dark area and bright corners.  In R/G this is opposite and much more subtle but nevertheless it's there.  It's circular rather than polygon.  Do you think this still indicates some raw cooking?  Or it is such a low level effect that it doesn't have any practical impact?


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#78 sharkmelley

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Posted 01 March 2024 - 08:15 PM

Hi Mark,

 

In the flat B/G images, there is a circle of dark area and bright corners.  In R/G this is opposite and much more subtle but nevertheless it's there.  It's circular rather than polygon.  Do you think this still indicates some raw cooking?  Or it is such a low level effect that it doesn't have any practical impact?

You raise an important point! 

 

What you are seeing there is colour shading i.e. a shift in colour towards the edge of the sensor.  This is almost certainly caused by pixel crosstalk, which is the effect where photons entering green pixels end up producing an electron in the adjacent red or blue and vice versa.  This effect is very dependent on the angle at which light strikes the sensor.  My conjecture is that the raw cooking on earlier cameras was intended to correct for this problem, for instance as described in this paper.  Sony used a polygon method, probably quite similar to what they patented here.


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#79 sharkmelley

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Posted 02 March 2024 - 04:49 AM

I need to make an apology and a correction regarding the Sony A7R4.  Back in post#24 I showed this image of coloured rings in flats provided by Cloudy Nights member @xonefs:

 

SonyA7R4_rings.jpg

 

I said back then that there is no sign of the dreaded Sony coloured polygons and this is still true.  But I've now determined the cause of the circular coloured rings and it's potentially a serious problem for deep-sky astrophotography.

 

The problem is immediately apparent in the RawDigger histogram of one of those flats:

 

SonyA7R4_histogram.jpg

 

Notice the regular histogram gaps.  This is caused by the camera digitally scaling the raw data and it's the direct cause of those rings.

 

 

The Sony A7R4 also damages stars, just like previous Sony mirrorless cameras.

 

I cannot recommend the Sony A7R4 for deep-sky astrophotography because of the damage to stars caused by the raw data filtering and because of the digital scaling that leads to coloured rings.

 

Mark


Edited by sharkmelley, 02 March 2024 - 05:11 AM.


#80 Digitaliz.se

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Posted 03 March 2024 - 12:04 PM

I thought astro flats were greyscale images.
I couldnt see gaps in Photoshop.
Are you doing anything extra i RAW digger?
Would like to test myself.

#81 sharkmelley

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Posted 03 March 2024 - 12:36 PM

I thought astro flats were greyscale images.
I couldnt see gaps in Photoshop.
Are you doing anything extra i RAW digger?
Would like to test myself.

The histogram you see in Photoshop is the histogram of data that has been digitally developed i.e. a significant amount of processing has been performed which will mix the colour channels and fill in the gaps.  RawDigger is the best app I know for displaying a histogram of the original raw data before any processing is applied.  Download the trial version (which is the full version but expires after the trial period) and display the histogram with Bin 1 resolution - you may need to restrict the data range displayed in order to display it with Bin 1


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#82 sharkmelley

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Posted 03 March 2024 - 01:57 PM

One other thing, in RawDigger, make sure you use "Linear X-Axis".


Edited by sharkmelley, 03 March 2024 - 05:53 PM.

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#83 astroboyabdi

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Posted 04 March 2024 - 07:30 AM

This is very good news.

Anyone test the a7cii which is the sony a7iv sensor but with the ai chip etc. If the a7cr is good then perhaps this maybe also good

#84 xonefs

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Posted 05 March 2024 - 03:59 PM

I suspect the c ii is good as well, but I don’t see the value for the lower res bodies when the R is not much more

#85 astroboyabdi

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Posted 05 March 2024 - 11:39 PM

it was more to double up as bird photography camera with the added bonus of being better in low light for nightscapes. What we need is is an a7v or a1 mark 2, the aiv is good but has star eater and no ai chip making it worse for both of the scenarios.

#86 Digitaliz.se

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Posted 06 March 2024 - 01:22 AM

Those that bought/are planning to buy A7R 5 or A7C R for DSO, are you also going to modd them? 

I'm thinking of the cost of buying state of the are daytime photography camera for the same price as a cooled FF astrocamera is crazy. Why not skip all the fuzz and just go all they way.
If I hade the money to buy a Sony A7R 5 for DSO photography, I would definitly buy a ASI6200MC instead. 
But since I am money aware, I went the route of getting A7III, A7R and A7R 4, all bought used and modded. Quite happy with them.

 

/Stefan



#87 xonefs

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Posted 06 March 2024 - 01:46 AM

Yes I will absolutely mod it. Mirrorless is for nightscapes and widefield (135mm and less) dso. Astro cams are a pain for this.

If you are looking for something mostly for a scope absolutely just get a zwo 6200.
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