Emd (electromagnetic diaphragm
EN: Emd (electromagnetic diaphragm
Designed for use with the digital data transfer of the EOS system made possible by the fully electronic mount, every EF lens incorporates an EMD that electronically controls aperture diameter. The EMD is a diaphragm drive control actuator comprised of a deformation stepping motor and diaphragm blade unit. Features include the following. Because the system is digitally controlled, its level of precision is far higher than that of mechanical linkage systems. The small rotor blades help deliver excellent start/stop response and control. Elimination of linkage shock from mechanical levers makes the system extremely quiet. The fully electronic mount system makes it possible to close down the aperture and confirm the setting and depth of field at the touch of a button. The EMD mechanism delivers superior durability and reliability. Its diaphragm control components are integrated into a single compact unit. And, the electronic control system allows a high degree of freedom in designing unit layout.
Canon glossary EU