We"ve designed this housing to offer one of the best performance to dollar purchases in the world. The Ikelite DSLR housing is a seamless blend of functionality, lighting integration, durability and waterproof integrity. TTL Advantage Other housings simply waterproof your camera. An Ikelite TTL housing improves your photos. TTL or "Through-The-Lens" flash metering means the camera controls flash duration to properly expose an image. Our built-in proprietary circuitry tells your camera that a TTL external flash is attached, allowing the camera to adjust exposure more accurately than with slave TTL strobes. Fiber optic slave flash units require the camera"s flash to fire every time. This creates a shutter lag as you wait for the camera"s flash to recycle in between shots, drains your camera"s battery life, and builds up heat inside of the housing. Instead, Ikelite electronics translate direct electrical impulses from your camera, triggering your strobe and precisely adjusting its power without the need to fire the camera"s flash. This eliminates the slave TTL strobe issues of signal interference, inconsistent exposure due to weak fiber optic transmission and false triggering caused by light rays bouncing off the water"s surface or your buddy"s flash going off. Exposure Adjustment Exposure adjustments directly through the back of the housing put the perfect shot within reach every time. Tweak your TTL exposure or take total manual c