I am trying to connect my 2012 iMac to an external display using a display port adaptor connected to a HDMI cable, the text on the external display looks grainy and off somehow. The external display itself is fine as I also have a PC connected to it and text reproduction is good. I have also connected a 2012 MacBook Pro to the display and it comes out the same.
So far I have tried changing the resolution of the external display and messed around with the settings of the display to no avail, nothing I can do seems to help.
I swapped out the HDMI cable for a different cable this one having a HDMI port on one side (connecting to my iMac) and a DVI on the other which would connect to the external display, this solved all my issues. Still not sure why I had problems with the HDMI cable but this problem has been solved.