For still photography, the Live View display on your Nikon D7100 appears by default as shown on the left. You can tweak the display in the following ways:
Change the data display: You can choose from the following display styles, each of which adds different types of information to the screen. Press the Info button to cycle through the styles.
Information on: This is the default mode, with data similar to what you see appearing for still photography. For movie recording, the display instead shows data related to movie settings.
Information off: Press the Info button to view only the major exposure settings, as shown on the right.
Framing guides: Press Info once more to display a grid over the scene, as shown on the left in the following figure. The grid is helpful when you need to precisely align objects in your photo.
Virtual horizon: This tool helps you make sure the camera is level to the horizon. A green line through the middle of the display, as shown on the right, indicates the level position.
Adjusting monitor brightness. Press the i button to display a settings control strip on the right side of the monitor.
Highlight the Monitor Brightness option, and press OK to display a screen that contains a brightness scale. Press the Multi Selector up or down to adjust the screen brightness and then press OK.
Monitor brightness has no effect on the actual picture brightness. So if you change the display brightness, don't use it as a gauge of exposure. In fact, you should leave this option set to the default, 0.