Sony A7S Concentric Banding

[MarkS]

So why haven't I produced any images recently?  It's because I currently have a processing backlog awaiting solutions to one or two Sony issues.

If you have a technical mindset then here is my latest discovery:
https://www.cloudynights.com/topic/557931-concentric-coloured-rings-caused-by-flats/?p=7853605

Unfortunately I have been using flats shot at ISO 100 to calibrate lights shot at ISO 10000.  This has created lots of artifacts related to concentric banding.  On any normal camera mixing ISOs would be no problem but this is Sony

I can't believe the amount of time I have wasted investigating and commenting on Sony issues.  I seriously wish I hadn't bought the Sony A7S.

Mark

[Carole]

Haven't read the link as yet, but despite the problems you have had with it, you have managed to produce vastly superior images and detail than you could get from any other OSC camera.

Will try to look at that link if my non technical mind can cope with it.

Carole

[JohnP]

Blimey Mark you are a real trooper with this camera - you figured out how many hours you worked trying to sort out the issues? What you need is someone that can download/ hack the camera software so you can see exactly what they are doing when processing the data in various Bulb/ non Bulb modes etc.

Like carole says you have still produced awesome images with this camera despite its issues.

John

[MarkS]

I honestly don't want to think about the time I've spent investigating issues.  It probably amounts to a whole month or two of solid evenings over the last 2 years.  At the moment I am really, really despondent - I'm on the verge of ditching the camera altogether and buying Nikon.  Nikon use the excellent Sony sensors but build a camera with fewer compromises.

On the other hand it is true that I've produced my best ever images with this camera.  But push the camera too far and it produces a mess.  I wanted to capture M81 M82 and the integrated flux nebula.  But when I stretch the image enough to reveal the IFN I get this:



Somehow the flats have led to purple and green swathes through the image.  But why?  I think it is related to the concentric banding issue.  I'm running loads to tests to get to the bottom of it and again it's consuming enormous amounts of time.

It's now just over 2 years since I introduced the world to the problem of Sony's "star eater".  It was a struggle back then with most people disbelieving me or not seeing it as an issue. However, in the last few weeks it has gone mainstream - some of the biggest bloggers have picked up the story:
http://www.sonyalpharumors.com/specific-a7sii-astrophotography-fix-request/
https://johnleathwick.wordpress.com/2017/04/29/sony-and-the-star-eater-algorithm-or-how-sony-crippled-the-worlds-possibly-best-cameras-for-astrophotography/
http://www.lonelyspeck.com/why-i-no-longer-recommend-sony-cameras-for-astrophotography-an-open-letter-to-sony/

The idea of mirrorless cameras is excellent in principle but Sony has given them multiple Achille's heels.

Mark

[Carole]

I can see your problem Mark, it looks like an uphill battle.  I think if I was in your shoes I'd have thrown in the towel on that camera by now.

Haven't you got a OSC CCD camera?  Why not get colour with that on one of your two rigs and get a Mono CCD camera on the other, with your skills you'd get some stonking results.

Carole

[MarkS]

I can see your problem Mark, it looks like an uphill battle.  I think if I was in your shoes I'd have thrown in the towel on that camera by now.

If I don't solve this problem then I'll be buying a full frame Nikon.

I do have a OSC CCD but I never use it because its sensitivity was no better than the Canon 350D I was already using.  The sensitivity of the Sony A7S was more than double and it's a full frame sensor so a typical exposure collected 4x as many photons as the Canon!  That's why the image quality was so much better. 

I've become far more demanding and want to extract really faint details and so I'm hitting a new set of issues.

However, if I ditch the Sony, I will really miss the incredible live view functionality.

Mark

[JohnP]

defo looks very messy - wouldn't know where to start on programming this. What's the specific Nikon model that you mention? Cheers,  John

[MarkS]

Nikon D810.  It's not cheap though
I'll need to modify it of course.

I also need to check that it doesn't have gappy histograms.  Unfortunately the D610 does has gappy histograms that could lead to concentric banding.  So it indicates that Nikon are heading the wrong way

Mark

[JohnP]

Ripping a £2,500 camera to bits would fill me with utter dread...! I reckon that you & Mike should team up with your analytical, mathematical & Software skills & his electronic abilities you could probably build/ design the ultimate astro camera. I've got access to workshops (metal) & CAD stuff...

[Carole]

Hi Mark, sorry to bang on about this (as I have also suggested it to you at other times), but you don't need the detail in the colour camera (OSC CCD), the colour is just a "wash", the detail comes from the Luminance or Ha filters. 

I was told this when I first switched over to CCD imaging, and I have seen the proof over and over again when processing.  I have even used my old DSLR images to provide colour and added Luminance to them.  You can just blur the DSLR images to smooth out the noise and then overlay the luminance on top.  So should work the same with a OSC. 

I agree the OSC CCD's do not give any more detail than a 350D, but used in combination with a Mono camera on a dual rig would give great images. 

The amount of detail you can get from a Mono camera is much much better than a OSC CCD. 

I will shut up now.

Carole

[MarkS]

Hi Mark, sorry to bang on about this (as I have also suggested it to you at other times), but you don't need the detail in the colour camera (OSC CCD), the colour is just a "wash", the detail comes from the Luminance or Ha filters. 

I agree the OSC CCD's do not give any more detail than a 350D. 

I was told this when I first switched over to CCD imaging, and I have seen the proof over and over again when processing.  I have even used my old DSLR images to provide colour and added Luminance to them.  You can just blur the DSLR images to smooth out the noise and then overlay the luminance on top.  So should work the same with a OSC. 

I've never believed that "washing" colour over deep luminance data produces the best results.  Sure, LRGB has traditionally been a quick way of obtaining a half decent image with high read noise mono cameras.  But the problem is that if the the colour data does not go as deep as the luminance data then the faintest structures can only be grey or blurred to death.  The result looks unbalanced to my eye and I've seen the proof over and over again in countless LRGB images.  That's one of the reasons I love OSC imaging - it always produces a balanced result with all visible structures having the correct colour and not fading to grey.

I'm not alone in thinking this way - Juan Conejero (the author of PixInsight) is a strong proponent of RGB imaging.  Sure, he provides support for LRGB in PI but he argues against using it.  There is a growing movement back to RGB imaging with mono cameras - especially with the current crop of low read noise CMOS cameras, since good noise-free R, G & B data is now more easy to obtain than previously.  If you're in doubt look at some of results I get with the uncooled low read noise Sony A7S, despite its many failings.  My style of imaging is a deliberate choice.  Maurice Toet even surprised Olly Penrice by going back to a DSLR from mono imaging but I'm certain this will be an increasing trend.

Coincidentally there was a very interesting thread on this very subject (LRGB vs RGB) on the Cloudy Nights forum recently:
https://www.cloudynights.com/topic/575319-lrgb-versus-rgb-a-fascinating-debate-at-the-highest-level/

However, in general I think it will prove difficult to win converts away from the LRGB "camp" because their mythology is so ingrained.

Mark

[Carole]

OK Mark, fair enough.  I suppose I was just keen to see what you would produce with a mono camera. 

Carole

[MarkS]

By the way,  if you want to follow progress (or non-progress) on what I'm calling the "Purple and Green swathes issue" then follow it on Cloudy Nights:  https://www.cloudynights.com/topic/576265-sony-a7s-purplegreen-swathes  I can't update it in more that one place.

Mark

[Carole]

Nightmare. 

I know it's a daft question but what does the image look like without flats applied, I know it will have dust bunnies and vignetting, but would be interesting to see the difference.

Also for arguments sake, have you tried applying the flats and no bias subs:
I know you technical people will shudder at this suggestion, but I have in the past stacked an image and it's come out really awful, perhaps something on the lines of what you are getting or worse.  Then some-one suggested to me to leave out the bias as it can sometimes muck it up.  I did exactly that and the image came out just fine.  This has happened to me on 2 or 3 occasions over the years though I must confess not on every image.  Just thinking "anything might be worth a try" if only for the sake of elimination. 

Carole

[Carole]

Any chance of letting us have some unstacked files and calibration files so we can "have a go" at them. 

Carole