i run 1780 × 692 with a 2:50:1 aspect ratio.
when pressing "rec" the cropmarks (black bars) dissapere and i dont know my framing.
is there any way to have the black bars remain eaven after pressing rec?
Yes. Check in case you have set overlays to be off when recording such as in the raw settings.
thx. will it affect performance much? with overlays on?
It can do, depending on what overlays you have running. Best to do a few tests with the settings you like a few times and playback the footage to check it before using it "in the real world" so you know its limitations.