The first thing I noticed about my NEX-6 was the fast speed of response of the shutter, the delay is very short indeed, After dong a bit of research I found that the shutter is 'opened' electronically and closed mechanically. The 'Front curtain shutter' entry in the settings menu controls this behaviour.
A focal plane shutter which is found in all DSLRs is just in front of the sensor and consists of two curtains. When the shutter button is pressed on a traditional DSLR the mirror is raised then the first curtain opens, starting at the top of the frame moving to the bottom. After a delay (the shutter speed) the other curtain sets off and finishes the exposure. For exposures above the maximum flash sync speed the closing curtain starts moving before the first curtain reaches the bottom.
For a mirror-less camera which has the shutter open all of the time for live view it would have to first close the shutter, clear the sensor, and then fire the first curtain to start the sequence. The Sony NEX-6 default setting is to have an electronic first curtain. Instead of closing the shutter, clearing the sensor and then starting the shutter sequence it simulates the first curtain by clearing the sensor from the top to the bottom at the same rate that the mechanical shutter would move. This has several advantages:
- The delay to the start of the exposure is very short and governed by how long it takes to focus, set the exposure and clear the sensor. When set to manual focus and exposure the delay is 23mS (see The Imaging Resource for timings).
- There is no mechanical movement in the camera at the start of the exposure which helps reduce camera shake. The NEX can be hand held at remarkably low shutter speeds.
- The wear on the shutter is halved.
The manual indicates that when using some A mount lenses with an adaptor the electronic shutter may cause problems, if that is the case change the 'Front curtain shutter' setting to off.
I belong to Storrington Camera Club and several of our members have gone for the Panasonic models. You are correct about the range of lenses for the Sony not being extensive, I decided that a larger sensor was more important for me.