Nikon D7100 is a 24MP mid-range, enthusiast-focused APS-C DSLR. The D7100 promises high resolution by making do without an optical low-pass filter in front of its 24MP CMOS sensor. It gains a more sophisticated 51-point autofocus system and a 7fps 1.3x cropped shooting mode that provides a 2x crop
Exposure Lock (AE-L Button) is the abbreviation stands for Automatic Exposure Lock. It is useful using automatic and semi-automatic shooting modes.