Abstract: A method of performing an absolute length calibration for an object located with or covered by a camera device in a mirror. The dimensions of the camera device are determined and an image is captured by the camera device of the camera device with the object. A length of the image of the object and the dimensions of the image of the camera device are measured and those measurements are used to calibrate the image.

Abstract: The invention relates to a method of performing an absolute length calibration for an object (20) located with or covered by a camera device (15) in a mirror (10), the method comprising the steps of determining dimensions of the camera device (15) based on the type of the camera device (15), capturing an image of the camera device (15) with an image of the object (20) with the camera device (15), measuring a length on the image of the object (20) and measuring dimensions of the camera device (15) from the captured image, and using the determined dimensions of the camera device (15), the measured length of the image of the object (20) and the measured dimensions of the camera device (15) to calibrate the length of the object (20).