The negative that Natalie cuts in the darkroom and takes is from a black and white roll of film. When she discards that negative in the final scene, the negative is from colour film.
The photographs taken at the beginning of the movie are seen as telephoto images, yet the camera being used has a normal 50mm lens attached.
In many of the driving scenes where Natalie is wearing sunglasses, the camera rig on the front of the car can be seen reflected in them.