Correctly made rectangular or square lens hoods are generally more efficient than cylindrical or conical ones because those shapes closely resemble the shape of the photograph. However, rectangular or square lens hoods should not be used with zoom lenses whose front elements rotate as the focal length is changed, as the hood will rotate as well, blocking parts of the angle of view. The same also applies to petal lens hoods. For these types of lenses, only cylindrical or conical lens hoods will work effectively.