New 27 inch iMac used as monitor for PS3

Greetings!

I am trying to use my 27 inch iMac as a display for the Play Station 3. I have a Mini DisplayPort to HDMI cord connected to both and the iMac does't do anything. I looked at the display in system preferances and there is no AirPlay Mirroring device connected. I also tried to press Command+f2 and there was no change. Is there anything else to try? Thanks.