A set of RGB and Ha light frames of the Horsehead were calibrated, aligned, stacked, and stretched by Garrett Grainger. The initial stacked and stretched RGB and H-alpha images are shown below. Both the RGB and H-alpha images were captured using a DSLR.
The goal is to enhance the RGB image using the H-alpha image. This example replaces the luminance of the RGB image with the luminance H-alpha image. The background is then neutralized and color adjusted.
Initial stacked and stretched RGB and H-alpha DSLR images left and right, respectively.
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Step 1
- Color | Split Colors is used to access the red, green, blue, and luminance of the RGB image. The initial H-alpha luminance image is shown top right.
The L, R, G, and B components of the RGB image are exposed using Split Colors.
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Step 2
- The L, R, G, and B components of the RGB image are exposed and displayed using Split Colors to setup Color | Combine LRGB.
- The initial H-alpha luminance image is also shown.
H-alpha luminance ready to use with R, G, and B components.
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Step 3
- H-alpha luminance is selected as the Luminance component on Combine LRGB then a left-click on the H-alpha luminance image sets the L part of the RGB image.
- Press Apply on Combine LRGB to rebuild the RGB image using the H-alpah image as the luminance component. This creates the LRGB image.
- At this point it is generally best to adjust the brightness and contrast stretch of each of the L, R, G, and B components so that the color balance and background levels are near their final values. After each adjustment to the components press Apply to rebuild the LRGB image.
- Step 4 below compares the origianl RGB image with the LRGB image created by this step.
H-alpha image used as the luminance of the RGB image.
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Step 4
- Initial RGB image left and output from Combine LRGB right with H-alpha as the L component.
Compare RGB image left with Ha as luminance component of RGB image right.
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Step 5
- Color | Color Balance is used to neutralize the background. Select Neutralize Background then left-click on a background area away from the nebula to neutralize the background.
Neutralize red background of the LRGB image.
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Step 6
- Adjust the color sliders on Color Balance to set the color to match your preference.
- The background level of the H-alpha luminance image could be increased in step 3 above to show more detail in the final image.
Adjust color using the Red, Green, and Blue Sliders on Color Balance. Initial RGB image left and color adjusted LRGB image right.
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