I have an iMac 27' late 2015
AMD Radeon R9 M380 2 GB
My secondary screen is a Lenovo L28u-30
Native resolution 4K, 3840 X 2160
Max scaled display resolution I can get is 1080p
Looks terrible.
Help please.
iMac with Retina 5K display, macOS 10.14
What exact cable are you using?
I didn't know the Mini DisplayPort was the same as the Thunderbird 2 socket. I bought the cable you suggested, and it has fixed the problem. Many thanks.
Use a Mini DisplayPort to DisplayPort Cable, such as:
https://www.startech.com/cables/mdp2dpmm6
The Mini DisplayPort end plugs into a Thunderbolt port on the iMac.
Thanks, I was using a standard HDMI cable with Thunderbird 2 Adaptor. I have purchased a Mini DisplayPort to DisplayPort cable, and, hey, fixed. Thanks for the help.
Secondary screen resolution issues
