The D3100 is equipped with a new Nikon DX-format CMOS image sensor and a new image-processing engine, EXPEED 2, both developed by Nikon. The CMOS image sensor offers an effective pixel count of 14.2-million pixels (D3000: CCD image sensor with 10.2-million effective pixels) and enables capture of high-definition images exhibiting superior image quality with extremely detailed rendering and rich tones. The camera also makes the most of its standard sensitivity settings up to ISO 3200 (D3000: ISO 100-1600) and additional increases up to HI 2 (ISO 12800 equivalent), with shooting under dim lighting, such as in the evening or indoors, as well as with sports scenes of rapidly moving subjects.

EXPEED 2 is Nikon's new image-processing engine, developed by refining the concepts, know-how and technologies regarding digital images that Nikon has spent years cultivating. It maximizes the performance of the CMOS image sensor to suppress noise in still images and movies and produces images that faithfully reproduce vivid colors.