Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Nebulosity colours all messed up

astrophotography beginner dslr imaging
  • Please log in to reply
23 replies to this topic

#1 ThatsMyCoffee

ThatsMyCoffee

    Vostok 1

  • -----
  • topic starter
  • Posts: 134
  • Joined: 15 Dec 2017
  • Loc: Czech Republic

Posted 17 January 2018 - 03:55 AM

Just starting out with imaging.  Took a series of shots of M42 (as every newbie does, right?)

 

I've followed the workflow outlined in the Nebulosity 4 tutorials and I got a few nicely stacked images.  BUT...  What's with the colours?  My raw files were preprocessed, later converted to colour.  But the colours are not even close.  The beautiful Blue glow around M42 comes out as yellow!

 

Can anybody point me in the right direction?  Perhaps a cut and paste of your workflow?

 

Here's what I've followed:  https://www.stark-la...ssing_HowTo.pdf

 

 



#2 einarin

einarin

    Viking 1

  • -----
  • Posts: 892
  • Joined: 23 Dec 2016

Posted 17 January 2018 - 04:08 AM

There's a white balance setting in Nebulosity. Have you tried that ?



#3 ThatsMyCoffee

ThatsMyCoffee

    Vostok 1

  • -----
  • topic starter
  • Posts: 134
  • Joined: 15 Dec 2017
  • Loc: Czech Republic

Posted 17 January 2018 - 04:56 AM

There's a white balance setting in Nebulosity. Have you tried that ?

 

I haven't.  When should that be done?  Before any pre-processing or at the end, on the final stacked image?

 

For those that use a DSLR:  What colour temperature do you shoot (on DSO's)?  I've been told to use Daylight, but it doesn't seem to work well.



#4 gilbertgrape87

gilbertgrape87

    Vostok 1

  • -----
  • Posts: 121
  • Joined: 30 Sep 2017
  • Loc: Mesa, AZ

Posted 17 January 2018 - 05:01 AM

Assuming you are capturing RAW, white balance doesn't matter as all that does is provide EXIF data at that point. Can you upload the master light image for people to take a look at?

#5 gbeaton

gbeaton

    Ranger 4

  • -----
  • Posts: 399
  • Joined: 06 Oct 2016
  • Loc: Montreal

Posted 17 January 2018 - 06:04 AM

In the preferences, there is a DSLR White Balance setting but its only compatible with some Canon models. I use "straight colour scaling" which doesn't do white balance (because I have Pentax DNGs that are not supported). My understanding is that most of these astro image processing software ignore the colour balance anyway. You have to do it after stacking. Also, if you have a light pollution filter, it will through off the balance.

 

With Nebulosity:

 

Batch lights (flats, darks)
Batch demosaic

Auto grade. Delete > 2.5 HFR

Batch align&stack
Image crop
[Synthetic flatten by division if necessary but means light pollution probably high]
Adjust Colour Background (Offset)

[Auto colour balance if necessary]

DDP or Curves for stretching - Set black/white in levels between each stretch.
Export to Lightroom/Photoshop or do further processing in Neb



#6 ThatsMyCoffee

ThatsMyCoffee

    Vostok 1

  • -----
  • topic starter
  • Posts: 134
  • Joined: 15 Dec 2017
  • Loc: Czech Republic

Posted 17 January 2018 - 07:19 AM

 

Batch lights (flats, darks)
Batch demosaic

Auto grade. Delete > 2.5 HFR

Batch align&stack
Image crop
[Synthetic flatten by division if necessary but means light pollution probably high]
Adjust Colour Background (Offset)

[Auto colour balance if necessary]

DDP or Curves for stretching - Set black/white in levels between each stretch.
Export to Lightroom/Photoshop or do further processing in Neb

Thanks for that.  No normalization of Intensities?

 

In preferences I have "Stock 350D, 20D" selected (default, I haven't touched it) for white balance.  No clue what that or the other choices mean.  Can anybody decipher these?



#7 ThatsMyCoffee

ThatsMyCoffee

    Vostok 1

  • -----
  • topic starter
  • Posts: 134
  • Joined: 15 Dec 2017
  • Loc: Czech Republic

Posted 17 January 2018 - 07:29 AM

Here's what I'm dealing with.  I've stacked 4 times now, with different options...still with horrible colours.  The RAW images look blueish, almost purple  (FYI, I'm slightly colourblind.  Doesn't help!)

 

Don't stress about the grain/noise.  My intervolometer died and I was camera limited to 30 second subs.  Had to bump up to 3200.

 

M42 V4 binned


#8 gilbertgrape87

gilbertgrape87

    Vostok 1

  • -----
  • Posts: 121
  • Joined: 30 Sep 2017
  • Loc: Mesa, AZ

Posted 17 January 2018 - 04:26 PM

If you upload a the stacked Tiff, I'll take a look at it later tonight and I'm sure other people will want to take a look too.

That's just to address whether or not it's correctable though. I've got no clue as why it's starting off like that.

#9 ThatsMyCoffee

ThatsMyCoffee

    Vostok 1

  • -----
  • topic starter
  • Posts: 134
  • Joined: 15 Dec 2017
  • Loc: Czech Republic

Posted 17 January 2018 - 05:44 PM

If you upload a the stacked Tiff, I'll take a look at it later tonight and I'm sure other people will want to take a look too.

That's just to address whether or not it's correctable though. I've got no clue as why it's starting off like that.

 

 

My workflow doesn't involve saving a stacked Tiff.  Is that a preference that I should have set?



#10 gilbertgrape87

gilbertgrape87

    Vostok 1

  • -----
  • Posts: 121
  • Joined: 30 Sep 2017
  • Loc: Mesa, AZ

Posted 17 January 2018 - 06:02 PM

The single file you have after step 6 in the workflow document you posted. Save that as an uncompressed file. This is your "master light". Your process may not explicitly tell you to save here, but do it and upload that file to Dropbox or something similar and share the link here.

#11 gbeaton

gbeaton

    Ranger 4

  • -----
  • Posts: 399
  • Joined: 06 Oct 2016
  • Loc: Montreal

Posted 17 January 2018 - 09:25 PM

 

 

Batch lights (flats, darks)
Batch demosaic

Auto grade. Delete > 2.5 HFR

Batch align&stack
Image crop
[Synthetic flatten by division if necessary but means light pollution probably high]
Adjust Colour Background (Offset)

[Auto colour balance if necessary]

DDP or Curves for stretching - Set black/white in levels between each stretch.
Export to Lightroom/Photoshop or do further processing in Neb

Thanks for that.  No normalization of Intensities?

 

In preferences I have "Stock 350D, 20D" selected (default, I haven't touched it) for white balance.  No clue what that or the other choices mean.  Can anybody decipher these?

 

No, you only need to normalize intensities if you shot at a different ISOs in your set of lights.

 

The colour looks like you have no colour balance so Neb is just doing straight colour conversion. Did you get a dialog asking for a matrix (default = 1:1:1)? If so then you need to get the colour conversion matrix for your camera from DXO. The 350D, etc. are Canon models. What is your camera?



#12 ThatsMyCoffee

ThatsMyCoffee

    Vostok 1

  • -----
  • topic starter
  • Posts: 134
  • Joined: 15 Dec 2017
  • Loc: Czech Republic

Posted 18 January 2018 - 02:52 AM

No, you only need to normalize intensities if you shot at a different ISOs in your set of lights.

 

 

 

The colour looks like you have no colour balance so Neb is just doing straight colour conversion. Did you get a dialog asking for a matrix (default = 1:1:1)? If so then you need to get the colour conversion matrix for your camera from DXO. The 350D, etc. are Canon models. What is your camera?

 

 

Yes, I do get that dialog.  My camera is a Nikon D5100, shooting AdobeRGB.

 

I've found the colour response data from DXO, but the chart is for sRBG.  My current thought is to change my in-camera setting.  Neb4 is probably expecting that.


Edited by ThatsMyCoffee, 18 January 2018 - 03:30 AM.


#13 gbeaton

gbeaton

    Ranger 4

  • -----
  • Posts: 399
  • Joined: 06 Oct 2016
  • Loc: Montreal

Posted 18 January 2018 - 06:46 AM

Sounds like you have the same problem as us Pentaxians. I assume you are using DNG files. Unfortunately DNG is not as standard as it should be and Neb is expecting a colour matrix that is not there. You have to use the DXO matrix. Actually, I use (colour matrix X white balance matrix) - both on DXO - to give a colour balanced output. After stacking I just do background offset. Read carefully, the DXO matrix converts to sRGB "primaries". This gives you the colour conversion you are looking for. You will not be limited to the sRGB colour space which has limits on the intensity and saturation of colours.

 

If you use a filter, you can create your own white balance matrix or just balance after stacking, which is what I am doing now.



#14 ThatsMyCoffee

ThatsMyCoffee

    Vostok 1

  • -----
  • topic starter
  • Posts: 134
  • Joined: 15 Dec 2017
  • Loc: Czech Republic

Posted 18 January 2018 - 06:57 AM

Sounds like you have the same problem as us Pentaxians. I assume you are using DNG files. Unfortunately DNG is not as standard as it should be and Neb is expecting a colour matrix that is not there. You have to use the DXO matrix. Actually, I use (colour matrix X white balance matrix) - both on DXO - to give a colour balanced output. After stacking I just do background offset. Read carefully, the DXO matrix converts to sRGB "primaries". This gives you the colour conversion you are looking for. You will not be limited to the sRGB colour space which has limits on the intensity and saturation of colours.

 

If you use a filter, you can create your own white balance matrix or just balance after stacking, which is what I am doing now.

 

My originals are .NEF

 

Tonight (clouds willing) I will try to shoot sRGB and see if that makes any difference.  Even if that works, I'm tempted to force the colour matrix manual entry.  That way I can use the DXO measured numbers, which I'm guessing will be more accurate than a default conversion.

 

My aim is to keep the output as close to visual as possible, then change the colour if desired.



#15 gbeaton

gbeaton

    Ranger 4

  • -----
  • Posts: 399
  • Joined: 06 Oct 2016
  • Loc: Montreal

Posted 18 January 2018 - 08:05 AM

You should use DNG if you can. If Neb handles it then that is the best. Trust the manufacturer, they know what they are doing.



#16 ThatsMyCoffee

ThatsMyCoffee

    Vostok 1

  • -----
  • topic starter
  • Posts: 134
  • Joined: 15 Dec 2017
  • Loc: Czech Republic

Posted 18 January 2018 - 08:35 AM

You should use DNG if you can. If Neb handles it then that is the best. Trust the manufacturer, they know what they are doing.

 

NEF is the default for Nikons.  There is no way for me to choose DNG, in-camera.



#17 gbeaton

gbeaton

    Ranger 4

  • -----
  • Posts: 399
  • Joined: 06 Oct 2016
  • Loc: Montreal

Posted 18 January 2018 - 12:19 PM

Really??!! Wow. I’m shocked

#18 ThatsMyCoffee

ThatsMyCoffee

    Vostok 1

  • -----
  • topic starter
  • Posts: 134
  • Joined: 15 Dec 2017
  • Loc: Czech Republic

Posted 20 January 2018 - 01:48 PM

Still no solution to this.  I did find an Adobe DNG converter.  It still didn't help.  Every time I demosaic in Neb, it goes haywire.  I did a test shot in daylight and played for hours.  I could get something 'close' to normal colours, but the workflow was just stupid.  Too many steps and it still wasn't good enough.

 

What I ended up doing is converting to TIF.  The colours and white balance were GOOD.  The bad news is that my already noisy 6400 iso images got even MORE noise.  Couldn't put my exposures past 25 seconds without blurring.  So I had to crank it up.  :(   I think a guide camera is in my future...

 

All things considered, I think it turned out rather well.

 

M45


#19 gbeaton

gbeaton

    Ranger 4

  • -----
  • Posts: 399
  • Joined: 06 Oct 2016
  • Loc: Montreal

Posted 21 January 2018 - 10:37 AM

Applying the colour conversion matrix does increase noise a little but it necessary to convert RAW. I've worked on this a lot - tried DNG converter too. The required matrix is missing in the RAW file. Trust me, use the DXO matrix for the batch colour conversion, and make custom colour adjustments after stacking. Good luck.



#20 ThatsMyCoffee

ThatsMyCoffee

    Vostok 1

  • -----
  • topic starter
  • Posts: 134
  • Joined: 15 Dec 2017
  • Loc: Czech Republic

Posted 21 January 2018 - 11:54 AM

Applying the colour conversion matrix does increase noise a little but it necessary to convert RAW. I've worked on this a lot - tried DNG converter too. The required matrix is missing in the RAW file. Trust me, use the DXO matrix for the batch colour conversion, and make custom colour adjustments after stacking. Good luck.

 

I'm sure you're able to manipulate the colours to make them seem 'ok', but this workflow makes no sense.  Screwing up the colours, then bringing them back?  There must be a better way.  I'm not giving up yet...

 

The raw data is good.  We just need a way to get it out.  Nikons are popular enough that *somebody* must have sorted this out.  Just have to find that somebody!



#21 Brass Hat

Brass Hat

    Sputnik

  • -----
  • Posts: 42
  • Joined: 17 Jul 2017
  • Loc: Southern California

Posted 21 January 2018 - 08:52 PM

Northlincsastro.org has a good work flow for nebulosity. I use a canon camera, but it might help.


  • ThatsMyCoffee likes this

#22 Brass Hat

Brass Hat

    Sputnik

  • -----
  • Posts: 42
  • Joined: 17 Jul 2017
  • Loc: Southern California

Posted 23 January 2018 - 07:57 AM

http://www.astropix....p/settings.html here are basic settings for canon dslr by jerry lodgriss. I started with these settings. I noticed you are using adobe rgb instead of rgbs. Read what it says about that. Hope it has some usefull info.



#23 Jon2070

Jon2070

    Lift Off

  • -----
  • Posts: 16
  • Joined: 30 Jan 2018

Posted 13 February 2018 - 05:09 AM

I've had similar problems with NEF files from my Nikon D750, I convert everything to TIFF files now prior to stacking and that seems to solve the problem.


  • gilbertgrape87 likes this

#24 gbeaton

gbeaton

    Ranger 4

  • -----
  • Posts: 399
  • Joined: 06 Oct 2016
  • Loc: Montreal

Posted 13 February 2018 - 10:50 PM

 

Applying the colour conversion matrix does increase noise a little but it necessary to convert RAW. I've worked on this a lot - tried DNG converter too. The required matrix is missing in the RAW file. Trust me, use the DXO matrix for the batch colour conversion, and make custom colour adjustments after stacking. Good luck.

 

I'm sure you're able to manipulate the colours to make them seem 'ok', but this workflow makes no sense.  Screwing up the colours, then bringing them back?  There must be a better way.  I'm not giving up yet...

 

The raw data is good.  We just need a way to get it out.  Nikons are popular enough that *somebody* must have sorted this out.  Just have to find that somebody!

 

Its not screwing up the colours. Its necessary to convert from the native colour space of the camera (and separate the overlapping colours in the sensor cells) to a standard colour space like sRGB. A colour conversion matrix (CCM) is necessary and the DXO matrix is THE matrix that is missing in the DNG file. The CCM could be determined from the matrix in the DNG file but some of the astro software out there just doesn't do it. So fortunately there is DXO. You can use their matrix - its based on actual testing. The (slight) addition of noise exists in all colour conversions. Its a fact of life.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: astrophotography, beginner, dslr, imaging



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics