Why does my computer screen get dim during the day and bright at night?

Everytime I open my Lenovo Yoga (windows 8.1) it adjusts the screen based on surrounding light. I would prefer it to be bright all the time, or at least let my pick my own brightness level. I can't find any settings for it. It's pissing me off. Help!

Added (1). I found it! I looked at the advanced power settings, expanded the display section and found the controls for adaptive brightness. I turned adaptive brightness off and it was fixed!

Check that you have enable any light saving software or not, may be it is f.lix or this type. May go to control panel and adjust the brightness in display setting