The Nikon D3100 is a 14.2-megapixel DX format DSLR Nikon F-mount camera announced by Nikon on August 19, 2010. It replaced the D3000 as Nikon's entry level DSLR. It introduced Nikon's new EXPEED 2 image processor and was the first Nikon DSLR featuring full high-definition video recording with full-time autofocus and H.264 compression, instead of Motion JPEG compression. It was also the first Nikon DSLR to provide high-definition video recording at more than one frame rate.
Nikon D3100 with the Nikon 18-55mm zoom lens.
The Nikon DX format is an alternative name used by Nikon corporation for APS-C image sensor format being approximately 24x16 mm. Its dimensions are about 2⁄3 those of the 35mm format. The format was created by Nikon for its digital SLR cameras, many of which are equipped with DX-sized sensors. DX format is very similar in size to sensors from Pentax, Sony and other camera manufacturers. All are referred to as APS-C, including the Canon cameras with a slightly smaller sensor.
CMOS image sensor of the Nikon D90
The Nikon D40 is a DX-format camera. Here, the DX-sized image sensor is exposed.
Vignetting produced by using a DX-format lens on a full-sized 35mm frame.
Nikkor DX lenses are marked with the DX logo.