Imac does not detect 2560 x 1440 resolution
I recently got a Benq PD2500Q monitor with a screen resolution of 2560x1440. But in system preferences it only shows 1080p I even pressed the option key on the scaled button.
I have an Imac 21" mid 2014 and a Macbook pro mid 2010 and both have the same issue.
How can I get the correct resolution on my display?
Specs: Benq PD2500Q Mac OS X 10.13.4 Connecting with MiniDisplay Port to HDMI
iMac, macOS High Sierra (10.13.3)