I find it really hard to focus manually with the D750 Even with the focus aid arrows and dot It's just not accurate enough I think for the lens/aperture I was using ( Zeiss ZF.2 Planar 50/1.4) Has anyone tried replacing the screen with the K-3 style screen from Focusing screens.com? Any thought on whether it works, how hard is the install and is there a better way to manually focus On the D750 - I've tried using the built in screen but it's not really made for this purpose