Nikon D5100 Reference Manual - Page 176

a: Autofocus a1: AF-C Priority Selection G button ➜ A Custom Settings menu When AF-C is selected for viewfinder photography (0 39), this option controls whether photographs can be taken whenever the shutter-release button is pressed (release priority) or only when the camera is in focus (focus priority). Option G Release F Focus Description Photos can be taken whenever the shutter-release button is pressed. Photos can only be taken once the camera has focused. a2: Built-in AF-assist Illuminator G button ➜ A Custom Settings menu Choose whether the built-in AF-assist illuminator lights to assist the focus operation when lighting is poor. Option On Off Description The AF-assist illuminator lights when lighting is poor. AF-assist illumination is only available when both of the following conditions are met: 1. AF-S is selected for focus mode (0 39) or single-servo autofocus is selected when the viewfinder is used in AF-A mode. 2. e (Auto-area AF) is chosen for AF-area mode (0 42), or an option other than e is chosen and the center focus point is selected. The AF-assist illuminator does not light to assist the focus operation. The camera may not be able to focus using autofocus when lighting is poor. A See Also See page 41 for information on using the AF-assist illuminator. Information on the shooting modes in which AF-assist is available may be found on page 216. See page 201 for restrictions on the lenses that can be used with AF assist. L 158