My first time out throwing the Sony A7s into Picture Profile 7 (PP7) SLOG which shoots crazy flat and has a minimum ISO of 3200. Keep in mind most people hesitate to use ISO 1600 on the Panasonic GH4 and here on the A7s SLOG your minimum ISO is 3200.
Outdoors with bright light pretty much everything will be washed out unless you can add an ND filter (I did not bring one), stop down the aperture, or increase your shutter speed. Indoors under very dim lighting it's pretty amazing. The tricky part though will be your post workflow which I think I failed pretty miserably at.
In the video above i'm just using what FCPX offers, but coloring the SLOG footage is not as straightforward as I thought. I'll have to find some better tools, and I hear many rely on plugins like FilmConvert. I'll have to keep experimenting and practicing.
As far as the Metbones Canon EF Mark IV adapter that I used to pair my Sigma 18-35mm (in crop mode) I had all types of issues. Maybe I need a firmware upgrade on the Metabones but the entire day was pretty frustrating. The recordings would stop every few seconds especially once focus peaking or zebras would kick in. Without being able to use Zebras or Focus Peaking (because of the adapter) I think I failed at getting decent focus on many of my shots. Until this adapter is a little more stable, i'm hesitant to use it on a project. I think I may just have to stick to Sony Lenses.
I can tell battery life is going to be an issue so i'll have to look into external power. The only reason I was able to get through the day is because the Metabones adapter kept failing and I had to continuously shut down the camera. So far the images from the camera seem great if I can just figure out a better workflow or tool for grading. I can't wait to try the 4K via HDMI out with an Atomos Shogun recorder, but the next time out i'll have to bring an ND filter and perhaps only use Sony Lenses.