Hello guy.
I have a little issue with me Sony VAIO laptop after installing Windows 8. In fact I did not have this issue when i installed it 1st time, (meaning I was running Windows 8 previously on this machine without this issue).
The Issue:
I can not control the brightness level by it's default short keys (Fn+F5,F6), meaning when i press those keys screen adjustment animation is appearing on Max. level but the screen is going dark! I can control it from Power options though! but as soon as i touch those keys Fn+F5 or Fn+F6, the screen is going dark again.
All the other Fn + .... keys are working properly,, I have installed all the necessary drivers and utilities for them (as I always was doing previously). I am installing:

1st [Setting Utility Series]
2nd [Sony Shared Library]
3rd [VAIO Event Service]
4rth [VAIO Control Center]

I read in some forums that by Turned off Display Brightness from [Image Quality] menu in [VAIO Control Center] is solving this issue (which was reported only while using Windows 8), but the problem is taht I do not have that [Image Quality] menu in my [VAIO Control Center] and II don't remember if I had it on my previous installation of Windows 8.

Thanks for reading all this, hope someone will have a solution which will work for me.
Have a great day