I'm at my wits end on this. I've gone through two different macs and two different displays trying to fix this issue. The goal:
I want to connect my 2015 Macbook pro to a 4k Samsung display at 60hz.
I'm currently using a Mini-Displayport to Displayport adapter. If I use an HDMI cable at 30hz the picture is perfect but the picture is choppy. If I use the Mini-DP to DP adapter I get 60hz, but also really bad washed out colors and banding / dithering issues. I've tried every color profile available and none work to address this issue. The display is almost completely unusable this way and it looks like a 1990s progressive-scan LCD. At 30hz on HDMI it looks perfect.
I've googled and searched everything I know how to search.
What am I doing wrong and what do I need to do to get this display to work?