Through-The-Lens (TTL) metering is a light metering system used in cameras that measures the light passing through the lens. This system allows for more accurate exposure readings compared to external light meters, as it takes into account the lens's characteristics and any filters. In photography, through-the-lens metering (TTL metering) refers to a feature of cameras whereby the intensity of light reflected from the scene is measured through the lens; as opposed to using a separate metering window or external hand-held light meter. In this beginner's guide, we'll explore what TTL metering is, how it works, and its importance in photography.