Big DSLR sensors are stitched together

[The Thing]

Deep Sky Stacker has always had an option to include Dark Flats in the calibration but I had never read a convincing argument for bothering. Now I have one

[RobertM]

I do have similar bands in the upper left quadrant, but they seem to be much much fainter (with 20 frames and flattened with Pixinsight DBE).  There is also very faint evidence of a vertical line

It looks to me like these are at the limits of the lithographic sensor production process of this technology, could also be that the limited production runs also introduce tolerance variations.

Its a real pain but I'm glad you now seem to have a solution.

Robert

[MarkS]

I have now concluded that I can never calibrate these bands away.

You can find the full gory details in the Cloudy Nights thread I started:
http://www.cloudynights.com/topic/519941-sony-a7s-split-sensor-and-banding/

You will also see that I'm not the only A7S imager to hit this issue.

I now have lots of data that I'm never going to be able to properly process.  I am NOT amused.

Mark

[Fay]

Mark your Cloudy Nights thread was quite scary to read. thing is would Sony take any notice as you have voided the guarantee. do you think there is a big change you get this banding on all full frame sensors, with longer exposures?

[MarkS]

Mark your Cloudy Nights thread was quite scary to read. thing is would Sony take any notice as you have voided the guarantee. do you think there is a big change you get this banding on all full frame sensors, with longer exposures?

I wish I knew the answer to that question.  I am ready to junk the Sony A7S and to never buy another Sony again.  Trouble is, how can I be sure that I wouldn't get the same problems with a full frame Nikon (which will also use a "stitched" Sony sensor)

Mark

[Carole]

What a nightmare Mark, just read the CN thread.

It isn't even as if the banding is consistently the same in each exposure otherwise you could perhaps write some sort of banding removal calibration.  I presume the banding is on the lights as well as the flats?

Carole

[MarkS]

It isn't even as if the banding is consistently the same in each exposure otherwise you could perhaps write some sort of banding removal calibration.  I presume the banding is on the lights as well as the flats?

Yes, the banding appears in the lights as well as the flats.  The worst thing is that I've now proved that the width of the bands will vary from light frame to light frame as the light pollution levels change during the night.  So there is no hope of ever calibrating it out.

Mark

[The Thing]

Looks like it's APS-C from now on then.

[MarkS]

Looks like it's APS-C from now on then.

Canon 7D MkII is a very tempting proposition.

[RobertM]

OMG what an issue !!!  It will affect all Nikon FF sensors as well as Sony (and whoever else uses the same technology).  I wonder whether any Nikon users have noticed.  Does it change over time as some seem to infer on CN or do you think that's a Red-Herring ?

Did you use bias, darks as well as the flat frames ?

I'll do some similar tests with mine when I get time in the next day or two.

I feel really bad about this since it was me who introduced you to the camera in the first place !

Well the Nikon 810Da is supposed to be for astrophotography so it would be interesting to see if they have the same problem.

Robert

[Carole]

I am presuming this only affects the large format sensors as both my CCD cameras have Sony chips.

Carole

[MarkS]

OMG what an issue !!!  It will affect all Nikon FF sensors as well as Sony (and whoever else uses the same technology).  I wonder whether any Nikon users have noticed.  Does it change over time as some seem to infer on CN or do you think that's a Red-Herring ?

It's a red herring

Did you use bias, darks as well as the flat frames ?

There's no hint of banding in the bias or darks unless you do a 20min dark, for instance.

I feel really bad about this since it was me who introduced you to the camera in the first place !

No hard feelings!

I am presuming this only affects the large format sensors as both my CCD cameras have Sony chips.

Yes, only large sensors have "stitching".

Mark

[RobertM]

All your images with that camera have looked superb to me and I've never noticed any artifacts.  Is the issue showing up now or have you just managed to process it out before ?

Robert

[MarkS]

All your images with that camera have looked superb to me and I've never noticed any artifacts.  Is the issue showing up now or have you just managed to process it out before ?

The only images I've posted are the images where the banding is not too much of a problem.  The Cepheus Shark image (earlier in this thread) is one of 3 or 4 images waiting for a solution to the banding issue.  It's been a long road to understanding the problem but now I've finally demonstrated there is no easy solution, I really don't know what to do.

I was hoping that experimentation would lead to a potential solution. Unfortunately, experimentation has shown the problem to be intractable

Mark

[RobertM]

That's a real friggin "^"%$^%$ !!!

It's difficult to understand that it can't be calibrated out but if you can't find a solution then it's a bit of a dead end.  I know you're very determined to solve this but could you sell the camera as modded for infrared ?

Robert