So your questions/concerns interested me, so I decided to do a little test. I mounted my D600 and 50/1.4 G on my Gitzo 1258 tripod with RRS BH55 head. I set the camera to a 2 second timer (I do not have a remote release for this camera yet). I took one picture with the mirror down, and another with LV. The timer was active on both shots. I took shots at the following shutter speeds:
I took a picture of a water bottle that had sharp small text. The bottle was approximately 2.5-3' away from the sensor. I used an aperture of F5.6 which I believe is the sharpest for the lens I used. I manually focused the lens in LV mode zoomed in.
At 100% view there was a very slight difference between mirror down and LV. I do not believe that the difference was significant enough to notice on common sized prints. Here are the shots from 1/25. All of the pictures were pretty similar looking all the way down to 1/2.5, so I am not going to bother posting them all. The files were converted using NX2 and saved as 100% quality jpegs.
This interested me too. I intend to test with D800 at the weekend (i don't have a D600); I will test as follows:- camera resting on a table and all shutter release via remote release.a) 3 second shutter delayb) LVc) no shutter delay, single shot moded) no shutter delay, quiet shot mode
The idea of resting it on a table is to see how much camera movement the mirror slap imparts to the camera. Hand held would only be a test of my technique.Maybe also try on sturdy tripod and/or loose tridod head.