Hello I have an HP Z27n 27" display and it connects to my Mac with a displayPort to mini-displayPort cable. Before this Mac I had a MBP 13" from 2011. I had several resolution choices in El Capitan. For health reasons I was working on a resolution of 1600x900 and I had these other options: 1920x1080, 1360x768 and 1280x720 in addition to the default resolution for the display. Now that I have a MBP 15" from 2015 and El Capitan too I only get 3 video resolution choices for this monitor: 2560x1440, 1080p and 720p on both 60 and 50Hz. How can I get other resolutions like the ones my previous Mac was giving me? I am specially missing the 1600x900 resolution that worked perfectly for my eyes on this screen. Thanks a lot for your help.