Vertebral implants for spacing apart vertebral members. According to the method, upon receipt of a user request to compose a message, a screen is displayed with a recipient field for a recipient address, an associated label to indicate that the recipient field is for a recipient address, and a message body field for holding message content. The exposure control mechanism comprises a diaphragm made up of diaphragm blades movable on a plane perpendicular to an optical axis in opposite directions to define a diaphragm aperture, and an ND filter made up of at least two ND filter elements having different transmittances.