N900 camera sensor
Hardware
The main camera is a ET8EK8 by Toshiba. The datasheet for this part is not publicly available.
The camera is a 5MP imager, with a Dual LED flash.
It is compatible with the N96, N85,N79 and N900. [1]
The service manual for the n900 indicates that the camera can be replaced. In principle this would allow upgrading the camera, however it is perhaps unlikely that a compatible camera of better quality will be easily available. There is also the obvious warranty issues - the camera is not a user serviceable part.
It is connected via a multiplexer to the single camera bus on the CPU, along with the front camera. The two cannot be used at once.
This lens is considerably smaller than the minimum physical requirement for a true 5MP camera.
Software
The lens cover on the phone can be sensed by the phone, to open the Camera camera application automatically.
This can be overridden - see this post
In PR1.2, the camera performance improved substantially in dark conditions.
The driver presents the camera as a video4linux device - /dev/video0.
The camera is used by several applications, including the built in camera application, a photo translation app and mbarcode.
Several applications augment the functionality of the camera - lfocus allows finer control of the camera focus and a flashlight application.
Gdigicam is used along with gstreamers Camerabin element to take pictures normally.
See the documentation for more information.