Author Topic: Correct PixInsight DSLR CR2 RAW Setting Question  (Read 539 times)

Offline jimwaters

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Correct PixInsight DSLR CR2 RAW Setting Question
« on: 2018 December 05 15:36:43 »
I use a Ha modified Canon 6D with a clip-in IDAS LPS D1 filter.  Is this the correct setting if I want to use a Custom White Balance?


Offline pfile

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Re: Correct PixInsight DSLR CR2 RAW Setting Question
« Reply #1 on: 2018 December 05 17:22:55 »
im not sure if white balance is applied when the image is kept in an undebayered state. can you post the command line that PI puts on the console when you open a CR2 with these settings?

rob

Offline jimwaters

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Re: Correct PixInsight DSLR CR2 RAW Setting Question
« Reply #2 on: 2018 December 05 18:29:18 »
open "file:///C:/Users/JTWaters/Desktop/2018_12_05/_MG_6009.CR2"
Reading 1 file(s):
C:/Users/JTWaters/Desktop/2018_12_05/_MG_6009.CR2
Reading metadata: done

Camera ........... Canon EOS 6D
Timestamp ........ 2018-12-06T02:34:54Z
Exposure ......... 1/800s
ISO speed ........ 100
Focal length ..... 2e+02 mm
Aperture ......... f/2.8 = 71 mm
Author ........... Jim Waters
CFA pattern ...... RGGB
Raw dimensions ... w=5568 h=3708
Image geometry ... x=72 y=38 w=5496 h=3670

Raw decoding parameters:
Output mode ............... cfa
Auto crop ................. disabled
White balancing ........... camera
Auto rotate ............... disabled
Output image .............. w=5568 h=3708 n=1 Gray

Reading RAW data: done
Scaling colors: done
Pre-interpolating: done
Converting to RGB: done

Offline pfile

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Re: Correct PixInsight DSLR CR2 RAW Setting Question
« Reply #3 on: 2018 December 05 22:21:49 »
shoot, i forgot that PI does not use dcraw anymore to import CR2 files.

honestly juan might have to answer this question. i looked thru the source code for the RAW file handler and i'm not totally sure how it interfaces with libRaw - i don't know what libRaw is going to do if you ask for CFA but also ask for a white balance to be applied. the answer is not in PI's source code.

i suppose you can find out if this works by setting some really extreme custom WB (like on an orange card) and then opening an image with and without that custom WB and see if you get something different when you debayer the CFA image PI gives you...

at any rate, usually the answer to this question is that you don't want/need to bother with custom white balances when using a DSLR for astrophotography but of course you might have some reason for wanting to do this.

rob

Offline jimwaters

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Re: Correct PixInsight DSLR CR2 RAW Setting Question
« Reply #4 on: 2018 December 05 22:29:15 »
Thanks for the info.

I am thinking that I want to use a CWB to offset the color shift of the IDAS LPS D1 filter before integration, calibration, stacking ...etc.  Color correction can be difficult to correct post integration and stacking.

Or is it always best to shoot RAW and deal with color corrections later.

Offline jimwaters

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Re: Correct PixInsight DSLR CR2 RAW Setting Question
« Reply #5 on: 2018 December 05 22:30:37 »
How would I contact Juan?

Offline pfile

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Re: Correct PixInsight DSLR CR2 RAW Setting Question
« Reply #6 on: 2018 December 06 09:04:53 »
he'll either post in the thread or he won't - that's how it goes.

anyway color correction is not super difficult post integration; it's what everyone does. the problem is that even if you eliminate any color biases from the filter, you will probably have atmospheric/light pollution effects causing color shifts anyway. so those still have to be dealt with and doing color correction twice would be a waste of effort.

PI has excellent tools for color calibration including the newest one - PhotometricColorCalibration - which analyzes the stars in your image to white balance the image against known white references. but you can start with the more old-school flow of BackgroundNeutralization followed by ColorCalibration. more than likely you'll have to start with DBE or ABE on the integrated image to get rid of any light pollution gradients. there are many tutorials on the web describing these flows...

rob