A key problem that plagues cera self-calibration, nely that the classical self-calibration algorithms are very sensitive to the initial values of the cera intrinsic pareters, is analyzed and a practical solution is provided. The effect of the cera intrinsic pareters, mainly the principal point and the skew factor is first discussed. Then a practical method via a controlled motion of the cera is introduced so as to obtain an accurate estimation of these pareters. Feasibility of this approach is illustrated by carrying out comprehensive experiments using synthetic data as well as real image sequences. Unreasonable initial values can often make self-calibration impossible, yet a precise initialization guarantees a better and successful reconstruction. Trying to obtain a more reasonable initialization is worthwhile the effort in cera self-calibration.