  Context. Magnetic Bright Points (MBPs) are small-scale magnetic features in
the solar photosphere. They may be a possible source of coronal heating by
rapid footpoint motions that cause magnetohydrodynamical waves. The number and
size distribution are of vital importance in estimating the small
scale-magnetic-field energy. Aims. The size distribution of MBPs is derived for
G-band images acquired by the Hinode/SOT instrument. Methods. For
identification purposes, a new automated segmentation and identification
algorithm was developed. Results. For a sampling of 0.108 arcsec/pixel, we
derived a mean diameter of (218 +- 48) km for the MBPs. For the full resolved
data set with a sampling of 0.054 arcsec/pixel, the size distribution shifted
to a mean diameter of (166 +- 31) km. The determined diameters are consistent
with earlier published values. The shift is most probably due to the different
spatial sampling. Conclusions. We conclude that the smallest magnetic elements
in the solar photosphere cannot yet be resolved by G-band observations. The
influence of discretisation effects (sampling) has also not yet been
investigated sufficiently.
