Somewhere around "f1.2", I find it ,much easier to use a rangefinder to focus a fast 50 than either an SLR or mirrorless camera. Over 10 years ago, bought a Canon 50/0.95 off Ebay, mounted it to my body right out of the box, everything was spot-on. With the EP2, I just cannot focus the F1.2 Nikkor.
Here's a glimpse into the morning time in my home this morning. Both taken with 50/0.95 Noctilux wide open on the Sony A7R, which so far I seem to be able to focus fairly well without peaking or magnification.
Kids eating chocolate chip waffles and playing Minecraft before getting ready for school:
On the Df- I use the menu to select a non-CPU lens and to format a new card. Otherwise, I like the dials. I wish camera manufacturers would publish the API and template source code. I'd have it simplified.