Lesson Description
When using a color camera for astrophotography, a residual green cast is common after stacking, especially after stretching.
In this lesson, you will learn to neutralize that green cast without losing the object’s natural colors, using the adjustment Reduce green with behavior of the type SCNR.
In addition, you will see a “more pro” flow for protecting nebulae, apply the effect only to the background using a mask and leave a clean integration.
As a bonus, you will also use it to improve star colors when they turn magenta or appear greenish after processing.
What you will learn
- Apply Reduce Green (SCNR) in a new layer and adjust the intensity with opacity.
- Repeat the adjustment several times when the dominant is strong, building up the effect.
- Protect the nebula, reverse the selection and apply the adjustment only to the background with Apply Mask.
- Correct problem areas by painting on the mask e integrate blurring it.
- Use the same adjustment to restore more natural star colors (without treating the issue as an optical halo).
Pro Tip:
When you work “more pro”, blur the mascara or not before deciding: it is the difference between a neutral background and an obvious clipping around nebulae/structures.
Practical Checklist
- Create a new layer, apply Reduce Green (SCNR) and adjust the force with opacity.
- Protect nebula → feather several times → reverse selection → Apply Mask → apply Reduce green only at the back.
- Blend the mascara and, if necessary, repeat the process in a new layer and blend downwards when natural.
Technical Glossary
Feather (fade): Smooths the edge of a selection so that the transition of a mask is not “cut off”.
Green cast: A residual greenish tint that often remains in the background after stacking and stretching, especially when using a color camera.
SCNR: A selective reduction method designed to remove residual green and balance color in astrophotography.