I have scoured the internet with the same problem and achieved mixed results based on different approaches.
I can confirm that it appears to be a problem between what image the PC is sending and what processing the TV then does - or doesn't do with this image
This is on the HTPC still having the problems.
O/S: WIn 7
Video Card: XFX HD 7750, obviously using HDMI out..
HDTV/Monitor: Sony Bravia KDL-46W4500 (46" LCD purchased 2009)
I also experienced the same darkness color issue on a 2012 Samsung 27" being fed all sorts of resolutions from a Samsung Series 3 laptop via HDMI. I spent 4 months deployed for work without being able to sort out the issue on that TV/monitor.
Recently I found someones post that suggested I find the option within the TV menus to essentially change the label or name of the input on that HDMI selection. Doing this on the Sony TV didn't change a thing. I renamed it 'PC' and saw no difference. However! Once I found the option on the Samsung 27" with Samsung Laptop and selected "HDMI-PC" it was perfect! The option could only be found by pressing the input button on the remote and then pressing the 'tools' button as it is a specific 'tools' menu for the input selection screen.
I suspect as my Sony TV is a little older this setup option didn't have the same effect and was just for the sake of naming conventions and user comfort. The Sony has got a VGA input available and when this is utilised the picture looks great, it really appears as it should with the HDMI cable. The Sony even gives you specific menu options available only when the VGA input is used. The website below explains what must be changed in order to view a PC image properly on the Sony however the "[Scene Select] to [Graphics]' instruction can't be followed as my tv doesn't have that menu option.
I did change the [Wide Mode] to [Full] and set the [Display Area] to [Full Pixel], both these changes helped the image but didn't solve the problem of the darkness/color issue. I Also needed to remove the underscaling and set it to 0% through the Catalyst Control Center (CCC). Again, this helped but didn't make the image colors look right and still not the same as when I connected the VGA cable.
In CCC I have adjusting the Pixel format to RGB 4:4:4 Pixel Format Standarrd (Full RGB).
I have run the color management walk through in Windows 7 but each time I can't get the Gamma close to the example of "just right".
There doesn't appear to be an option online to update my TV's Firmware, the current version is:
If i try adjusting the TV brightness, color settings it will look correct in one scene but not the next. Playing Skyrim is nearly impossibly because the dark areas are losing detail. To get Skyrim correct means that windows itself and most TV shows are Far too bright.
Has anyone got any other ideas?
Thanks for any help available!!