Performance Evaluation of a 33 Megapixel Alpa 12 Medium Format Camera for Digital Close Range Photogrammetry

The accuracy of object reconstruction was tested with two medium format cameras made by ALPA of Switzerland. Both cameras have been equipped with a 33 megapixel Leaf Aptus 75 digital camera back and a 47 mm focal length Schneider Apo-Digitar lens. The first test was carried out with the lens in “normal” position. In the second test, the principal point of another Apo-Digitar lens type was decentred by a fixed amount of approximately 8 mm. Decentring the principal point of a lens can be of advantage for terrestrial applications. Both cameras reveal large accuracy of object reconstruction, checked against calibrated scale bars in a test field (according to VDI/VDE Guideline 2634). The accuracy of object reconstruction of the camera system with the decentred lens does not reach the same level as for the “normal” camera. * Corresponding author.