Nikon's rumored D400 DSLR is real, the author of an upcoming book on the camera has confirmed. A NikonRumors community member said he has contacted the author of the text and learned that the writer is under a non-disclosure agreement that will prevent him from discussing the camera until it's announced. The book itself is due in summer.

Little is known about the camera itself, though an update to the D300 will likely give it features both closer to and above the D3. Rumors hint that the camera will have the same light sensitivity, reaching up to ISO 25,600, and should have a sharper sensor near 15 megapixels. HD video has also been rumored, though whether it would scale to 1080p or else be limited to the 720p of the D90 is still uncertain.