Select Nikon cameras have an in-camera HDR (High Dynamic Range) mode so make sure to review your reference manual for complete details on setting your camera for HDR.
When shooting HDR (High Dynamic Range) with the D5100 DSLR camera, the camera automatically combines two exposures to form a single image that captures a wide range of tones, from shadows to highlights. The first exposure is darker (underexposed) and the second exposure brighter (overexposed). They are combined into one image that has a wider range of tones than can be captured in one exposure. HDR mode is only available with JPEG recording, not RAW (NEF) recording.
Along with choosing the exposure difference, the user is given the choice of Smoothing (high, normal or low). Smoothing refers to the look of the composite HDR image. High and normal produce a more natural look, whereas low produces an image with a more surreal look.