The Inverted Triangle Atmospheric Background is a type of background used in photography and video production. It is created by placing a light source behind the subject, and then using a reflector to bounce the light back onto the subject. This creates a triangle shape with the light source at the top, the subject in the middle, and the reflector at the bottom. This type of background is often used to create a dramatic, moody atmosphere, as the light source creates a strong contrast between the subject and the background. It can also be used to create a sense of depth and dimension in a scene.