For the best images, the receptor should be positioned parallel to the teeth and deep into the lingual vestibule or palatal vault; this is particularly important when rigid sensors are used because they are bulkier than film. For maxillary projections, the superior border of the receptor generally rests at the height of the palatal vault in the midline. Similarly, for mandibular projections, the receptor should be used to displace the tongue posteriorly or toward the midline to allow the inferior border of the receptor to rest on the floor of the mouth away from the mucosa on the lingual surface of the mandible.  The x-ray source to object distance should be as long as possible. This will enable the Xray photons to emerge in a straighter line in a less divergent beam, therefore producing more accurate shadow. The straighter the X-ray photon line, the less divergent the beam with a resulting image that is more accurate.