When Sony introduced their new G-Master lenses, they designed them to produce the highest resolution and pleasing bokeh. For anyone unfamiliar with “bokeh”, that’s not a word from the latest Minion movie; its the Japanese word referring to the visual.
Sony A7 / A7R: From Snapshots to Great Shots - Brian Smith - Google Books click on main image to see the ebook and also have a look at these settings for the A7; http://www.dpreview.com/forums/thread/3579827
I've just installed The Brass Signature Edition Tough Replacement Lens Mount onto the #SonyA7R. It certainly gives less movement on my CZ 24-70mm on first looks, lets see if it fixes those apparent light leaks too. Highly recommended if you are experiencing lens movement. https://www.fotodioxpro.com/tough-emount-signature-edition-2015-from-fotodiox-pro-replacement-lens-mount-for-sony-nex-emount-camera.html