Can we find Camera matrix, without running the calibration code?

Question

I would like to know if it is possible to know the camera calibration matrix anyhow , just by knowing it's specifications , without using camera calibration???

Answer 1

You can take a guess, but this will not replace a proper calibration, since every single camera is different--even if it is of the exact same type.

In your camera matrix, you have usually fx, fy, cx, cy (for square pixels). Take cx=w/2 and cy=h/2, where w and h are the width and height of your image, respectively.

For fx and fy, it is a bit trickier. Theoretically, we have fx = w*f_mm/w_mm, where f_mm is the focal length of your lens in mm and w_mm is the width of your CCD sensor in mm. However, since lenses are round and sensors usually not, you cannot just take the values from the specifications. There are tables that should give a good estimate for sensor width and height given the sensor size from the specifications, e.g. on Wikipedia. However, if the lens is mounted slightly different, these values are not true anymore.

With this, you will also not calibrate for distortions. It is highly recommended to do a proper calibration, e.g. with a checkerboard.