Author Topic: LRGB Combination - Request for Updated Procedure Suggestions  (Read 645 times)

Offline BenKolt

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Greetings!

Sorry if this topic has come up more recently than I've been able to identify, but through my searching I've only found some rather dated posts that don't seem to work well for me.  Therefore, I'm asking here for folks to post recommended procedures and best practices using PI for LRGB combination.

Specifically, I found old advice about the use of the RGBWorkingSpace process in its application to the RGB images as well as the L image prior to combination using the LRGBCombination process.  The old procedure, as I understand it, seems to result in an error using RGBWS.  Rather than to get into all that, let me instead ask for what's considered the best practice now.

1) Having built my RGB and L images separately, when should I combine them?  I've done this both early and late in the processing, even played around with combination of linear images, although my preference has been to combine later in the processing when both images are non-linear and have undergone many processing steps unique to each.

2) Is RGBWS still being used prior to combination?  If so, what is the best method to preserve the color balance of the RGB when combining with L?

3) I use LRGBC, unchecking the RGB boxes, only including the L image, usually including some noise reduction, and then applying the LRGBC process to the RGB image.  Is there another, perhaps, better method than this?

Thank you for updating me on this procedure, and I look forward to your responses.

Best Regards,
Ben




Offline BenKolt

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Re: LRGB Combination - Request for Updated Procedure Suggestions
« Reply #1 on: 2019 August 06 15:51:23 »
Greetings Again!

I guess my original post did not resonant well on the forum and stimulate an outpouring of response after all!

Let me ask my questions in a different way:

Please share your LRGB combination workflow!  When and how do you combine the L and RGB?  Do you use RGBWorkingSpace at all?  Please do not hesitate to provide much detail!

Thank you!

Best Regards,
Ben


Offline John_Gill

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Re: LRGB Combination - Request for Updated Procedure Suggestions
« Reply #2 on: 2019 August 07 00:05:04 »
Hi,

I process each filter stack separately and then end-up with integrated image for L, R, G, B or Ha, Oiii Sii.  I then do a StarAlignment on these images which will create the "Registered" images.  Then crop out the "black border"  (Select the image that requires the most crop, and mark the area with DynamicCrop.  Do not execute the process, but rather "push" the process icon to the workspace).  Now drop the process icon (DynamicCrop) onto each image.  This will crop all the images the same.  I then run ABE or DBE on each image followed by LinearFit.  Next I create a Lum mask and apply it to each image and then invert the mask.  I use MLT to reduce noise on each image and then remove the mask.  Now onto stretching the image.  You can use HistogramTransformation, MaskedStretch or ArcsinhStretch.  I use 2 applications of ArcsinhStretch (first a small stretch and then a further bigger stretch) and finish off with a little HistogramTransformation.  The images are now non-linear and can now be combined.

I normally do a quick ChannelCombination to get an idea of what the new image will looks like.  You can use PixelMath to combine the channels with different formulas to produce different results.  I mostly use LRGBcombination as I can use Ha as the L channel and then the RGB channels are mapped to HOO or SHO etc. You can  adjust the weights of each channel and adjust brightness and color saturation, plus get some Chrominance Noise Reduction.  I usually end-up fiddling for hours with LRGBCombination until I get the right channel mix, brightness and saturation.  Once I am happy with the combination image, I do the "normal" post-processing.

I hope this helps …

space is not black
John

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Offline wvanreeven

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Re: LRGB Combination - Request for Updated Procedure Suggestions
« Reply #3 on: 2019 August 07 02:29:43 »
You can eliminate the need to crop each image individually by doing the crop before the StarAlignment and then use that File or View as reference. This will crop the rest of the images while doing the star alignment.


HTH, Wouter

Offline dave_galera

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Re: LRGB Combination - Request for Updated Procedure Suggestions
« Reply #4 on: 2019 August 07 02:33:03 »
I recommend Warren Kellers book and the tutorials on this site http://www.pixinsight.com.ar/
Dave

Offline BenKolt

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Re: LRGB Combination - Request for Updated Procedure Suggestions
« Reply #5 on: 2019 August 07 08:58:55 »
Hi,

I process each filter stack separately and then end-up with integrated image for L, R, G, B or Ha, Oiii Sii.  I then do a StarAlignment on these images which will create the "Registered" images.  Then crop out the "black border"  (Select the image that requires the most crop, and mark the area with DynamicCrop.  Do not execute the process, but rather "push" the process icon to the workspace).  Now drop the process icon (DynamicCrop) onto each image.  This will crop all the images the same.  I then run ABE or DBE on each image followed by LinearFit.  Next I create a Lum mask and apply it to each image and then invert the mask.  I use MLT to reduce noise on each image and then remove the mask.  Now onto stretching the image.  You can use HistogramTransformation, MaskedStretch or ArcsinhStretch.  I use 2 applications of ArcsinhStretch (first a small stretch and then a further bigger stretch) and finish off with a little HistogramTransformation.  The images are now non-linear and can now be combined.

I normally do a quick ChannelCombination to get an idea of what the new image will looks like.  You can use PixelMath to combine the channels with different formulas to produce different results.  I mostly use LRGBcombination as I can use Ha as the L channel and then the RGB channels are mapped to HOO or SHO etc. You can  adjust the weights of each channel and adjust brightness and color saturation, plus get some Chrominance Noise Reduction.  I usually end-up fiddling for hours with LRGBCombination until I get the right channel mix, brightness and saturation.  Once I am happy with the combination image, I do the "normal" post-processing.

I hope this helps …

space is not black
John


Thank you, John!


Offline BenKolt

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Re: LRGB Combination - Request for Updated Procedure Suggestions
« Reply #6 on: 2019 August 07 09:00:40 »
You can eliminate the need to crop each image individually by doing the crop before the StarAlignment and then use that File or View as reference. This will crop the rest of the images while doing the star alignment.


HTH, Wouter

Thanks, Wouter.  This is exactly what I do.


I recommend Warren Kellers book and the tutorials on this site http://www.pixinsight.com.ar/

Thank you, Dave!