This blend mode simply adds the pixel values of the light over underlying lights (composited on the canvas).
See how the 3 colors mix to create white as the lights are added together.
See how 3 soft round lights are added to this HDRI map using add blend mode.
Add blend mode is ideal for adding lights and is the default blend mode for Round, Rect, Hex, Gradient Lights, Gradient Background and Picture Background.
Dark light has blend mode add with invert.
Use Add with the Invert option on to Subtract. This blend modes simply subtracts the pixel values of the light over underlying lights (composited on the canvas).
See how 3 soft round lights are subtracted to this HDRI map using add blend mode with invert option on. They darken the image.
