EMD
The Electromagnetic Diaphragm (EMD) is made to work with the fully electronic lens mount system to give you very accurate digital aperture control. The EMD is made up of an aperture-blade unit and a stepping motor that can be bent. In regular cameras, the aperture blades are opened and closed by mechanical levers inside the camera. The new system, on the other hand, can provide much more precise control. The aperture can be changed with an electronic dial on the EOS body or by sending a pulse of electricity to set the aperture value. The operation is smooth because there are no levers. With the invention of EMD, some very special lenses were made, such as the world's first* TS-E lens with automatic diaphragm, which was made in 1991 and received a lot of praise for being innovative.
Canon made the RF5.2mm f/2.8L Dual Fisheye lens in 2021. It was the company's first Stereoscopic 3D 180° VR lens and it had two 5.2mm fisheye lenses built in. The EMDs on the right and left lenses are separate and work together. So, electronic signals can control both EMDs at the same time, making it easy to change the exposure for both the left and right lenses.
