Evaluation of a Digital Non Metric Camera (canon D30) for the Photogrammetric Recording of Historical Buildings

This paper is about the evaluation of a digital non-metric reflex camera (Canon D30) for low cost applications in archaeology, architecture and cultural heritage. At present digital cameras of different geometric qualities are being routinely used for this purposes. The Canon D30 digital camera is a professional camera with a CMOS sensor of 3.2 Mp. Although camera resolution is relatively low, compared with more recent amateur cameras, the sensor is slightly smaller in size than conventional 35 mm film format. The focal length/angle of view conversion factor is approximately 1.6x compared to full frame 35 mm film format. This property makes very interesting the use of this camera in cultural heritage photogrammetric applications, where both accuracy and final image quality are quite important. The camera internal geometry has been solved by means of self calibration with own developed software. First self calibration was made at laboratory using digital target measurement at subpixel accuracy. Proportional accuracies with this method were between 1:20.000 and 1:30.000. But additional self calibrations where carried out with field control points. In this case, accuracy reached was poorest because images were manually measured on natural points, but it was for normal architectural/archaeological applications enough. As main drawback of this camera we can point out the low sensor resolution. So when camera/object distance increases or high oblique photographs are employed the image quality of the final product reduces considerably.