The Canon EF Lens to Sony NEX Camera Lens Mount Adapter Mark IV from Metabones attaches a Canon EF lens to a Sony NEX camera. It is referred to as a "Smart Adapter" because it retains electronic communication between the camera and lens and therefore provides automatic aperture control, EXIF data, image stabilization and autofocus. The adapter is powered by the camera body, so no external power source is required. The Mark IV provides the same functions as the Mark III but provides optimized performance and an improved internal structure.

The Smart Adapter IV offers two distinct operation modes: Green and Advanced modes. Each mode supports a different set of features and is selected when you mount the lens. Green mode is the default mode and it is designed to conserve battery power by limiting aperture diaphragm movements and image stabilization. Certain other functions are not available in Green Mode including Auto-Magnify MF Assist and DOF preview.