WHAT IS ACTIVE D-LIGHTING?
Active-D Lighting expands the dynamic range of your camera’s sensor Active D-Lighting is often best left off when shooting in RAW. There is a glossary. When strong lighting increases the contrast between bright and dark areas of an image. It causes the shadow and highlight details to be lost as shown in the image below.
The image on the left shows the balanced lighting achieved when Advanced D-Lighting is turned off. The image on the right was taken with D-Lighting turned on. Notice the dark areas in the foreground and background of the image.
WHEN TO USE ACTIVE D-LIGHTING?
Basically, it is used in low light conditions or extreme sunlight conditions to expose the image well without changing the other parameter to get the perfect details in the image.