It's not only on Sony computers. I'm using a Fujitsu Lifebook and have been having the same problem since I installed Windows 8 last night. I tried increasing the brightness several times, but it's stuck at practically minimum power.
Edit: I ended up disabling the adaptive brightness. Worked like a charm. I'll probably have to enable it again once the full version of Windows 8 comes out (assuming the adaptive brightness is fixed by then). Here's a tutorial on how to disable it.
Why the hell not if windows 8 cant their rubbish together and release updates and fixes to this buggy OS we need to do something.....I have an HP and have the same issue, I can even get used to 8 because I can't see anything...and I paid full price for the OS so for my money I want a product that works, am I wrong in assuming these issues should have been addressed prior to its unveiling on the public....
Hello. I also have a Sony Vaio, although it's an S series, and I had the same problem. Turns out that Sony Vaios have a feature to sense the brightness and automatically adjust display brightness. No matter what changes you make on the Windows 8 Power Plan, this feature will change them seconds later.
You can disable this accessing the Vaio Control Center, then go to Image Quality, and then set to OFF where it says "Display Brightness - Set whether to sense the brightnes and automatically adjust the display brightness accordingly". I got this from Vaio Support and worked nicely. Hope it helps.
Hello I have exactly the same problem but in my [FONT=Arial, sans-serif]VAIO Control Center I do not see any "[/FONT]Image Quality[FONT=Arial, sans-serif]" menu! Can you pleas tell me what should I install to get that option in my [/FONT]VAIO Control Center ?