Author Topic: LRGB Combination problem.  (Read 3868 times)

Offline cdesselles

  • PixInsight Addict
  • ***
  • Posts: 164
LRGB Combination problem.
« on: 2014 November 15 11:27:30 »
I recently tried to follow an example of color correction by using LRGB channel extraction, Linear Fit, and LRGB Combination.  Everything seemed to go well until the final reassembly of the image.  A complete workflow (as best my memory serves me) is below.

From a 32bit floating point TIFF OSC frame from a DSLR I did the following: 1) Extracted the Luminance channel, then minimized it for later work.  2) extracted the RGB channels into separate images.  3)Using Linear Fit, I selected the RED channel image as a reference, then accepted the defaults and applied Linear Fit to the Blue and Green channel images. 4) next using LRGB Combine I reassembled the R,G, and B, channel images into one RGB file. 5) on the resulting RGB file I applied Curves Transformation (Saturation) and a bit of Color Saturation to boost some reds and pinks, and then ACDNR to blur a bit of the background noise. Finally I applied Histogram Transformation using the STF settings to set the RGB image to non-linear. 

With the RGB done, I then moved on to the Luminance image I had extracted earlier to: 6) STF autostretch applied to Histogram Transformation. Then 7) Local Histogram Equalization to try for a bit more detail in the structure.

Lastly, (and this is where my problem arises) I opened LRGB Combination again, this time selecting only the Luminance channel image.  I then dragged the process icon triangle over to the RGB image to apply the combination.

This step failed --- I got an error stating the geometry of the 2 images did not match ---  What did I do incorrectly or what step did I leave out?

 :-\
Celestron CPC1100 - Canon 550D (T2i) and of course, Pixinsight!

Offline niteman1946

  • PixInsight Addict
  • ***
  • Posts: 234
Re: LRGB Combination problem.
« Reply #1 on: 2014 November 15 15:03:39 »
Try star aligning your L to the RGB just prior to doing the LRGB process.

Mark

Offline cdesselles

  • PixInsight Addict
  • ***
  • Posts: 164
Re: LRGB Combination problem.
« Reply #2 on: 2014 November 15 19:49:29 »
Possibly, but I tried a slight Dynamic Crop of the L image, then before processing it saved the icon to the workspace so I could apply the same crop to the RGB.  With matching crops the LRGB Combination worked.  But sine I started woth only one TIFF image, why should the geometry mismatch happen in the first place?
Celestron CPC1100 - Canon 550D (T2i) and of course, Pixinsight!

Offline niteman1946

  • PixInsight Addict
  • ***
  • Posts: 234
Re: LRGB Combination problem.
« Reply #3 on: 2014 November 16 04:29:21 »
I've had similar situations where the two images were originally aligned to the same single image.  And by the time i got to the LRGB Process, their geometries were incompatible.
Don't know why but a second star alignment did the trick for me.

Mark

Offline cdesselles

  • PixInsight Addict
  • ***
  • Posts: 164
Re: LRGB Combination problem.
« Reply #4 on: 2014 November 16 05:43:08 »
Well stranger things have happened to me in PI.  I'll keep the realignment in mind.  Thanks for the tip.
Celestron CPC1100 - Canon 550D (T2i) and of course, Pixinsight!