"Today, Sony confirmed a rumour – no doubt started as a result of pre-production tester leaks – that the A7S would have a completely silent all-electronic shutter mode. It’s completely free of all mechanical action and totally silent.
The silent shutter has been implemented as a firmware upgrade to the early production samples and future stocks, along with several other important firmware enhancements – all of which will have Sony owners wondering why improvements to their six-month old or one-year old purchases are not equally forthcoming. These are however improvements to a £2,100 camera body which will not hit the shops until the end of July 2014.
The firmware fixes and upgrades are:
α7S now offers a ‘Silent Shooting’ mode
ISO range for Movie Shooting extended to ISO100 – 102400, expandable to ISO100 – 409600
Dynamic Range extended to 15.3 stops as sensor RAW output
Sony A7S gets silent shutter upgrade | Photoclubalpha