I have a brand new 2015 MacPro laptop that i need to add a 2008 Samsung 27" monitor to for photo editing. I have connected the two with HDMI cables and do see the screen saver on the large monitor, but nothing else. What am I missing ? What other connecting cables are necessary?
When you see the screen saver, is your laptop also in screen saver mode? In System Preferences->Displays, do you see the second monitor?
I do. I did not realize that you have to slide your working screen to the right in order to view it on the large monitor. Guess I will get the hang of it eventually. Thanks for your response.
Glad to hear you solved it. Good luck.
Don't know which OS you're running but mostly the situation is that you have the option to have two separate desktops or to mirror your monitor to your MBP display.
Here's a support article for Mountain Lion and earlier:
OS X: How to use multiple displays with your Mac in Mountain Lion and earlier - Apple Support
connecting large monitors to Mac Pro laptops
