Green background after deBayering NEF files

[jbeyer]

I recently installed a purchased copy of PI on my iMac running OS X10.11.3 and after debayering Nikon NEF images they have an intense green background.  Previously I had been using a trial version on a Macbook Pro with the same operating system and without even realizing I needed to deBayer colors seemed to be fine and the processed/stacked images always had orange-tinged background.  Currently if I don't add the debayering step on my new computer I get no color - which I suppose is expected.  I did set the NEF / RAW profile to what was shown in the Pixinsight video tutorial (the one with no sound) right after I installed the program.  After I perform a background extraction with either the automatic or dynamic tools it strips the green out and the image seems to process OK from there. 

A thread was posted a year or so earlier from someone with the same observation and the resolution for them was to uncheck "create raw Bayer RGB image" in the Format Explorer.  This box is not checked on mine yet the green background is there.  I can reproduce the background by opening any NEF file in PI and just deBayering.

If the processing outcomes hadn't been so different using the same files between my laptop and iMac I'd almost think it was normal but clearly something is different in terms of file handing. 

Joe

[Alejandro Tombolini]

Hi Joe, welcome to the forum.
Let me see if I understand. When you apply STF with unlinked channels on your image, does it look fine? If that is the case, then you have to apply BackgroundNeutralization tool to correct it. (you also have corrected it by applying DBE with Normalization box unchecked)
I imagine that the difference between both machines could be related to different DSLR Settings, but not sure.
Hope this helps
Saludos, Alejandro

[jbeyer]

Thank you for replying so quickly.  Yes, unlinking the channels in STF produces a relatively normal appearing image. You are also correct that when applying DBE the Normalization box has been left unchecked.  I can easily move the BackgroundNeutralization step forward in my processing to improve image visualization.  I'll also compare the DSLR settings between the machines and look for any differences.  If I find anything of note I'll reply for other's future reference.  Thanks again.

Regards, Joe

[pfile]

i think this is pretty normal for any OSC and has something to do with the fact that there are 2 green pixels per bayer quad. i get this with my canon DSLR as well.

rob

[jbeyer]

I have seen this question come up in a number of forums and solutions seem to be inconsistent. Is there any reason Background Neutralization should not be used as the first step following preprocessing and image stacking?  Seems many people stress using DBE (or ABE) prior to neutralizing the green background. In my case it's often difficult to visualize what I need to do in DBE if the background isn't neutralized right away.

[pfile]

i think the emphasis on ABE/DBE is only because most people have LP gradients and trying to neutralize the background while the background is polluted with LP would result in an incorrect neutralization result. same with the next step, colorcalibration.

while it's a pain in the butt, what you could do is break out the 3 color channels, then linear fit the red and blue to the green channel, and then put the channels back together and do DBE. or just do DBE to the split channels and then recombine them after DBE. that way you shouldn't have any problem seeing what you are doing. you will probably have to do another DBE after recombination as when looking at the mono files it's hard to detect the more subtle gradients.

rob

[jbeyer]

Thank you.

[Alejandro Tombolini]

Hi Joe, as rob said if there is light pollution gradients on the image first correct it and then perform the Background Normalization.
To have a confortable visualization of the image when working with DBE unlink the STF channels.
This video of linear post processing may help.
Saludos, Alejandro.