Processing a single image
At the top of the "Stack" module are all the buttons that control the execution of stacking in Nebulb and, specifically, the button below is used to process a single image (the one displayed on the screen):
By clicking this button the image loaded in Nebulb is processed, thanks to which it is possible to apply light pollution reduction on that image (without stacking).
While the image is being processed (to estimate the light pollution it has) this button appears disabled (cannot be pressed) and in orange color:
And when the individual image processing is completed, this button is displayed in orange with a check mark. At this point the post-processing modules (right tool panel) are enabled so that the user can make any desired adjustments to the image, such as reducing light pollution.
IMPORTANT: In case multiple images have been imported, only the image selected as base by Nebulb (the one displayed on the screen) is processed by means of this button. The processing (stacking) of all images is done by the button to the right of this one.
In this other article you can see in more detail how to process a single image to reduce light pollution: https://help.nebulb.com/portal/en/kb/articles/how-to-reduce-light-pollution-in-a-single-image