Abstract
A study on the geometric stability and decentering present in sensor-lens systems of six identical compact digital cameras has been conducted. With regard to geometrical stability, the variation of internal geometry parameters (principal distance, principal point position and distortion parameters) was considered. With regard to lens decentering, the amount of radial and tangential displacement resulting from decentering distortion was related with the precision of the camera and with the offset of the principal point from the geometric center of the sensor. The study was conducted with data obtained after 372 calibration processes (62 per camera). The tests were performed for each camera in three situations: during continuous use of the cameras, after camera power off/on and after the full extension and retraction of the zoom-lens. Additionally, 360 new calibrations were performed in order to study the variation of the internal geometry when the camera is rotated. The aim of this study was to relate the level of stability and decentering in a camera with the precision and quality that can be obtained. An additional goal was to provide practical recommendations about photogrammetric use of such cameras.
Highlights
In recent years, improved resolution and sensitivity of photo sensors and decreasing costs have enabled the emergence of novel photogrammetric applications performed with many types of nonmetric cameras
One of the six cameras analyzed shows significant geometric instability, even without moving the objective lens. This instability may be due to faulty construction in the lens system that does not prevent the operation of the camera but does limit its potential for metrics use
The rest of the cameras have shown that variations of the internal geometry, during continuous use or after applying cycles off/on are comparable to those obtained with other cameras used in photogrammetric applications of medium or low accuracy
Summary
In recent years, improved resolution and sensitivity of photo sensors and decreasing costs have enabled the emergence of novel photogrammetric applications performed with many types of nonmetric cameras. Low-cost cameras, amateur cameras, semi-professional and professional cameras are being used for field applications [1], structural surveying [2], structural engineering [3], materials sciences [4], measurement systems [5,6] and aerial mapping [7]. These cameras, not initially designed for metric purposes [8], have technologies such as autofocus, zoom lenses, retrofocus construction and image stabilizers, which can potentially reduce their accuracy [9]. The analyses presented indicate that there are differences between the two lens types in terms of accuracy, precision and stability, suggesting that acceptable results can be obtained using zoom lenses, a fixed lens provides superior results
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