see also:

• the Olympus OM-D system and how to make the most of it

• although modern digital cameras have electronic sensors, most have a mechanical shutter in front of the sensor which controls how long the light hits the sensor and thus the exposure
• many cameras now also have a “silent electronic shutter” mode in which the mechanical shutter is disabled fully and the sensor itself times the duration it collects light

• the advantages of this mode are:
  • higher shutter speeds usually to 1/16,000th sec - or 1/32,000 with E-M1 Mark II (but scene exposure takes the full readout time still)
  • silent shutter
  • no shutter vibrations to move the sensor and blur the exposure
  • does not cause shorten the life of the mechanical shutter
  • often have a faster burst rate (E-M5II and E-M1 go to 11fps, while the E-M1 Mark II takes it to 60fps!)
• the disadvantages of this mode in cameras without global readout sensors (the case with most current cameras) are:
  • potential rolling shutter artefact when there is a moving subject, the subject is imaged skew angled not vertical - this has been much improved in the E-M1 Mark II but it is still there
    • the degree this occurs depends upon the speed of the sensor readout, some cameras such as the Panasonic GH3 have a long readout time of 1/10th sec in this mode resulting in substantial rolling shutter effect, GH-4 takes 1/30th sec, while the OM-D E-M5II takes 1/20th sec ¹⁾, the E-M1 Mark II takes ~1/50th sec
  • ISO may be limited to 3200 (no such limit with E-M1 Mark II)
  • flash sync limited (E-M5II is limited to 1/20th sec due to the readout time, while E-M1 II limited to 1/50th sec)
  • longest shutter speed may be limited to only a few seconds (no such limit with E-M1 Mark II)
  • sensor output may be reduced (this does not appear to be an issue with OM-D cameras)
    • eg Panasonic GH-4 reduces output from 12 bits to 10 bits with some reduction of dynamic range

• to reduce mechanical shutter shock blurring images at around 1/100th sec, many cameras allow the user to select a electronic first curtain so that the mechanical shutter is still used, but only to terminate the exposure.
• on OM-D cameras, this is selected in the Drive Mode menu