The fisheye images cover a field of view of 2pi steradians - ie the lens maps the entire hemishphere in front of the camera onto a circular image on the film. For images with the camera horizontal, the top of the image circle is directly above the camera. For images with the camera pointed straight up, the horizon right round the camera is just on the outer edge of the image circle. Striaght lines become curved in fisheye images, especially towards the edge of the field.