Mifune13

I have noticed with my GH4 (which I picked up about two days ago) that when in live view with the OLED and stopped down the screen appears to stutter. It seems like the more information I have on the screen the more jittery the image becomes. It seems like it is lagging. Is this created by a setting within the camera?

Which ones would you recommend, black or silver ring?

Hey - Recently just bought the GH4 and was looking at some Rokinon and SLR Magic lenses. I was wondering if I should get them MFT mount or purchase a speed booster and get the EF mount? I am assuming the crop factor will decrease if I get the EF and speed booster but the fact that I won't have to use a adapter with the MFT is great. Just want to get some thoughts on this? Also can anyone recommend other primes that are great with the GH4? Thanks