Once our luminance image is enhanced with HDR Transformation, Sharpening and Dark Structure Enhancements, we need to integrate this back into the original color image. The overall goal with luminance integration should be to

  1. Brighten the image without brightening to background.
  2. Increase the clarity of high signal areas

LRGB Combination

The LRGB Combination process is used to integrate the luminance channel with an RGB image.

This process simply requires the selection of the luminance image and then to determine the weights for lightness and saturation

  • Lightness: Increasing the number reduces the luminance brightness
  • Saturation: Decreasing the number increases the color

It is best to run through this a with a few different settings to identify the best result

Default (50/50) LRGB Combination
Default LRGB Combination Settings
55/45 LRGB Combination
55/45 LRGB Combination Settings
60/40 LRGB Combination
60/40 LRGB Combination Settings

The right option is up to personal preference.

What’s Next

Overall, spending the time to create an enhanced luminance definitely improves the overall quality of the image.


The next step is optional, and that is to reduce the star brightness with PixInsight Morphological Transformation.