High Quality Content by WIKIPEDIA articles! The Nikon D300 is a 12.3-megapixel professionalDX format digital single-lens reflex camera that Nikon Corporation announced on 23 August 2007 along with the Nikon D3 FX format camera. It replaced the D200 as Nikon`s DX format flagship DSLR. The D300 was officially discontinued by Nikon on September 11, 2009, being succeeded by the Nikon D300S, which was released July 30, 2009.