What is the difference between mechanical and electronic shutters, and which is the best to use?
Lewis Foster, Papcastle
BRIAN SAYS… A mirrorless camera image sensor provides a live feed to allow composition, exposure and focus to happen before the shot is captured, so the sensor must be uncovered most of the time, meaning the first physical shutter curtain is already open.
EOS R-series cameras have three modes of shutter operation: electronic 1st curtain, mechanical and electronic. Each has benefits and limitations. The default is electronic 1st curtain, where the first curtain is already open, so the start of the exposure is controlled by switching the sensor to image capture, and the end of the exposure is controlled by the second shutter curtain, after which the second curtain must be returned to the home position. This minimizes lag and reduces the viewfinder blackout time. The shape and smoothness of bokeh is less pleasing than if controlled by two physical shutter curtains.
The mechanical shutter option maximizes the quality of bokeh, and with two moving curtains it makes the most noise. As both methods use the shutter curtains, flash may be used, though sync speed is 1/3-stop less for mechanical shutter than for electronic 1st curtain mode.
Electronic shutter mode uses the sensor to time the exposure, and as the curtains don’t move, lag is minimal, viewfinder blackout is reduced, shots are silent and the continuous shooting frame rate is increased. Flash photography is not possible, except on the EOS R3, and the bokeh is less attractive than for electronic 1st curtain and mechanical shutter modes. Electronic shutter mode also enables faster shutter speeds up to 1/64,000 sec for the R3 and 1/16,000 sec for R7/R10.
Each mode has value for different things – bokeh is best with mechanical,while silent shooting and frame rate are best with electronic.