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Horizontal/oblique moire/coloured banding on Canon


rofus

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Hi all

I have a weird problem on my Canon 6D astro modded (filter removed and changed with clear glass by a professional not myself and done some time ago).

Basically as you can see from attachment (light stack and flat both stretched), I have some weird horizontal/oblique banding. I use darks and bias and flats, and as you can see is both on lights and flats (if I star align my lights without using any flat/dark/bias is there anyway).

The banding happens in any condition...freezing winter or hot summer, on scopes or lens, actually even without any lens in front. Seems to be always the same. I tried as well cleaning the sensor but is not the problem. I also tried using different batteries or the AC adaptor, same result. Also with SD or direct download via USB, and even in different cities/places!

Basically I have no idea what it is, what causes it, and how to get rid of it...flats don't work...is very subtle, and for faint objects/nebulosity if I need to really get all the data, it creeps out in final images and being 'coloured' (as you can see from the light) is almost impossible to eliminate.

Does anyone have any idea what causes that thing, what actually is, and possibly how I can solve it?

Screen Shot 2018-12-12 at 21.25.35.jpg

Screen Shot 2018-12-12 at 21.24.11.jpg

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1 minute ago, Davey-T said:

There are a couple of Canon banding removal actions available although not sure if this constitutes what's referred to as Canon banding as I think it's normally horizontal.

Dave

Thanks, yeah no those are different bandings, both PS actions and PI actions deal with the other and more well known vertical banding of Canon sensors.

This is something very different and quite peculiar...that's why I'm asking here hoping that someone has previously seen something like that...as I cannot find someone with a similar problem...!

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33 minutes ago, rofus said:

how I can solve it?

Hi.Hoping that someone can suggest a fix but you seem to have exhausted all optical culprits in the imaging train up to te sensor so maybe the next thing is to remove the glass replacement filter. If it's in contact with the sensor it's a similar effect as when you have two sheets of glass in contact; there are colour fringes due to te surfaces not being in total contact.

OTOH, it's not the 750d issue is it?

HTH and all the best of luck.

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19 minutes ago, alacant said:

Hi.Hoping that someone can suggest a fix but you seem to have exhausted all optical culprits in the imaging train up to te sensor so maybe the next thing is to remove the glass replacement filter. If it's in contact with the sensor it's a similar effect as when you have two sheets of glass in contact; there are colour fringes due to te surfaces not being in total contact.

OTOH, it's not the 750d issue is it?

HTH and all the best of luck.

Hi

thanks a lot for your reply. Actually I just checked the emails exchange with Andy Ellis (Astronomiser), who did the mod, and there was no replacement: he actually just removed the second filter, as he says the replacement (Baader mod) would cause reflections and is not recommended.

So there's just one glass, not two...I also tried asking him at the time, but he didn't reply to my last enquiry when I did all the tests and was still there (and it wasn't there before the mod). Apart from that the system works perfectly..but that is a big problem on faint objects.

Do you think is the first glass (the only one remained) touching the sensor? Andy had problems with my 6D, had to have it repaired after his mod because something went wrong, and he said he could not reproduce the problem (but he didn't try a full session or stretching the single shot to see the patterns emerge).

I'm actually a bit desperate with it as is obviously expensive and I cannot always go around the problem just pushing back the black in the background...

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5 minutes ago, alacant said:

Gotta be worth asking him to re-seat the remaining filter...

Yeah I wrote him again, as he never replied to my last email...eventually he did a job I feel he wasn't completely confident with, something broke (electronic part), took months to have it repaired from Canon and I think he lost some money on it, so I'm not holding my hopes...but I wrote again, because eventually I got the camera.

I highly doubt he wants to do the whole disassembling again considering he then stopped doing 6D mods..so this is why I'd rather first understand what it is before committing to anything like that...because then to test it you have no other option than reassembling and disassembling again..seems a never ending process to me.

And anyway weird that actually no one else has ever had that kind of problem...

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So similar interference on short exposures (flats) and on long exposures (lights) suggests a problem in the on-camera processing.

But it also looks like radio frequency intereference.

So take the camera off the scope, set it to AV,  point the camera without lens at a white surface, take a shot, and stretch like your example.

If it's clean then investigate your cable runs and other scope power supplies.

If dirty, last resort, clear all custom settings, try jpeg, try lowest ISO.

Michael 

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If you don't already have it, I'd suggest installing Magic Lantern (https://magiclantern.fm/) on the camera.

It opens a greater control of all aspects of the camera. I used the software to reduce\remove similar banding to yours on an old 300D

Sorry if I've missed this, but are your images raw or processed jpeg's ? (always use raw, imho jpg's are just for previews)

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59 minutes ago, Dr_Ju_ju said:

If you don't already have it, I'd suggest installing Magic Lantern (https://magiclantern.fm/) on the camera.

It opens a greater control of all aspects of the camera. I used the software to reduce\remove similar banding to yours on an old 300D

Sorry if I've missed this, but are your images raw or processed jpeg's ? (always use raw, imho jpg's are just for previews)

16 hours ago, michael8554 said:

So similar interference on short exposures (flats) and on long exposures (lights) suggests a problem in the on-camera processing.

But it also looks like radio frequency intereference.

So take the camera off the scope, set it to AV,  point the camera without lens at a white surface, take a shot, and stretch like your example.

If it's clean then investigate your cable runs and other scope power supplies.

If dirty, last resort, clear all custom settings, try jpeg, try lowest ISO.

Michael 

 

Julian: I always use only RAW, and I actually have Magic Lantern installed. How did you solve those problems? Any particular setting?

Michael: I tried that and the banding is still there, and at the time I also tried changing ISO without any luck...to me somehow it doesn't seem to be anything related to camera processing as that's always RAW...

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I've never seen anything like this.  It looks very odd and it certainly shouldn't be there.

That being said, are you absolutely certain that flats don't remove the problem?  In your example above, the flat is overcorrecting by a significant amount, evidenced by the bright dust spots and the dark vertical band through the centre.  Is there a possibility that the bands will disappear if you perform an accurate calibration with flats?

Mark

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On 16/12/2018 at 14:09, sharkmelley said:

I've never seen anything like this.  It looks very odd and it certainly shouldn't be there.

That being said, are you absolutely certain that flats don't remove the problem?  In your example above, the flat is overcorrecting by a significant amount, evidenced by the bright dust spots and the dark vertical band through the centre.  Is there a possibility that the bands will disappear if you perform an accurate calibration with flats?

Mark

Actually what you see on the flat is obviously a very stretched flat...I always take accurate flats following all common procedures...and actually they always worked wonderfully (also on my Nikon D750)....I just think is not something a flat can really correct because is way too "spread" and different?

Any suggestion about what I could try with flats taken in a different way?

As I said..it seems no one knows or ever saw something like that...I honestly struggle understanding this...

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Diagonal banding in CCD / CMOS  detectors is nearly always caused by interference from an electronic source whose frequency is close to the clock readout frequency of the detector.

Since you have eliminated the external power supply and see this with internal battery only then you have ruled out external sources and all that remains is something inside the camera.

If the issue appeared immediately after the camera was modified I would suspect a possible problem with the internal ribbon cables connecting the various boards inside the camera so that a ground connection is missing, maybe the ribbons are not fully homed in their respective sockets etc. Of course it might just be coincidence and nothing to do with the mod at all and a component has failed on one of the boards causing the problem.

If the camera modifier is no longer working on these cameras and you are not able or willing to pull the camera apart yourself perhaps a chat to a Canon service agent might be worth investigating ?

HTH

William.

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8 minutes ago, Oddsocks said:

Diagonal banding in CCD / CMOS  detectors is nearly always caused by interference from an electronic source whose frequency is close to the clock readout frequency of the detector.

Since you have eliminated the external power supply and see this with internal battery only then you have ruled out external sources and all that remains is something inside the camera.

If the issue appeared immediately after the camera was modified I would suspect a possible problem with the internal ribbon cables connecting the various boards inside the camera so that a ground connection is missing, maybe the ribbons are not fully homed in their respective sockets etc. Of course it might just be coincidence and nothing to do with the mod at all and a component has failed on one of the boards causing the problem.

If the camera modifier is no longer working on these cameras and you are not able or willing to pull the camera apart yourself perhaps a chat to a Canon service agent might be worth investigating ?

HTH

William.

Hi William

 

thanks your explanation makes a lot of sense. When the guy did the mod, he said that after reassembling everything the camera was not turning on anymore, so he had to send it to Canon and they had to fix/replace the main board.

The guy who did the mod still operates but doesn't reply as with me he had problems with months of delays, money problems, and eventually he said the 6D is too complicated so he doesn't work on them anymore.

I suppose I could contact the centre that actually fixed the camera after the mod and ask them..

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5 hours ago, rofus said:

Actually what you see on the flat is obviously a very stretched flat...I always take accurate flats following all common procedures...and actually they always worked wonderfully (also on my Nikon D750)....I just think is not something a flat can really correct because is way too "spread" and different?

Any suggestion about what I could try with flats taken in a different way?

As I said..it seems no one knows or ever saw something like that...I honestly struggle understanding this...

You may have misunderstood what I was trying to say.  I'm not saying there is anything wrong with the flat but that your image calibrated by the flat is looks overcorrected for one reason or another -  for instance the dust spots become bright instead of disappearing.  Are there dust spots in your lights?

There is a small possibility that a flat that corrects the dust spots properly will also correct the banding.  It depends on whether or not the banding occurs randomly or is fixed in place.  If it is some kind of electrical interference (which is likely) then it will be random and uncorrectable.

Mark

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4 hours ago, happy-kat said:

@Nigel G is this similar to what you experienced some time ago and wasn't it related to signal interference on the data cable?

This is different to my banding, mine are horizontal bands. nothing to do with cables, just Canon banding.

I removed the second filter to see if it helped, I got a much better full colour response but no change to the banding. There is a very tough bit of glass in front of the sensor after the 2 filters are removed. I doubt its damage to the front of the sensor.

Its a delicate job modifying cameras, I made a small mistake connecting one of the ribbon wires the first time I modified mine. Blew the main pcb. £100 mistake. Not a straight forward pcb swap either. 

This has vertical and almost diagonal bands, got a feeling it is a sensor problem though.

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You might want to contact Canon's Product Repair people in Stoke over your issue and asking for a quote to replace the sensor-https://www.canon.co.uk/support/consumer_products/repair/ They are very helpful and will also overhaul the camera as part of their service. From memory they even do a repair service while you wait but you pay more for such a rapid turnaround.

Some time ago I suggested to them they might want to consider doing filter removals to Canon DSLR's as an additional income stream for them.

Cheers,
Steve 

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  • 2 weeks later...

Hello and Happy New Year!

Thanks a lot for all your replies...it seems indeed everyone has a different idea about what's the problem..and I honestly am not sure if it's worth another repair...it could be easily in the region of several hundreds.

And last time it was at repair centre, they did not 'see' any problem because they don't test/do flats or that stretched images, so unless they know about astro they don't see the problem, as it's indeed only apparent on stretched images..

The original Canon repair service didn't reply to my enquiry, and the modder didn't as well...it seems one of those things no one want to deal with. I'm tempted to keep it and 'fix it' when to apparent in post processing as I did it till now (sometimes quite painful but in a way or another can be done..)

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