Is this problem happening on other games? or just dark souls, this game is a console port, and because of that there are some problems, for instance, to use 1080p it requires a fix... and that fix requires you to remove all the game effects on the game menu, and use only the config file from the fix.
Were you using that fix? if yes, you can tune the settings on config file for that specific game.
If this is happening in other games too i bet that you have not adjusted the gamma, or maybe your monitor/television isn't calibrated making those effect look worse than they really are.
excluding dark souls, try to run your games at your native resolution for better image quality, lowering resolution will fix some problems but you will be stretching the image.