Whilst browsing, if you hit the menu key (bottom left) it brings up a list of things such as 'New Window' and 'Add Bookmark' etc.
The option you're looking for is 'Brightness and colours'.
It isn't instantly visible, you have to scroll down the menu list.
Once in there, you can turn off the Automatic brightness and adjust it to your desired setting.
You can also change the colour level to 'Default' or 'Level 1' for added colour rather than the dull 'Level 3'.
If you didn't know it was there or that you could scroll down the list, I doubt you'd ever find it. Well hidden Samsung!