An experimental study of the efficiency of recently predicted photonic crystal (PhC) based spatial filtering is provided. Photonic structures are fabricated using a direct laser writing technique employing point-by-point modification by tightly focused femtosecond pulses in soda–lime glass. Such PhCs are characterized by using an s-coefficient – a parameter defining PhC filter efficiency. We explore the dependences of filtering efficiency on different laser writing conditions, such as irradiation peak intensity and the polarization of laser beam. In addition, we show that the PhCs can also exhibit even asymmetric shapes of voxels under particular conditions.