  The weak, turbulent magnetic fields that supposedly permeate most of the
solar photosphere are difficult to observe, because the Zeeman effect is
virtually blind to them. The Hanle effect, acting on the scattering
polarization in suitable lines, can in principle be used as a diagnostic for
these fields. However, the prediction that the majority of the weak, turbulent
field resides in intergranular lanes also poses significant challenges to
scattering polarization observations because high spatial resolution is usually
difficult to attain. We aim to measure the difference in scattering
polarization between granules and intergranules. We present the respective
center-to-limb variations, which may serve as input for future models. We
perform full Stokes filter polarimetry at different solar limb positions with
the CN band filter of the Hinode-SOT Broadband Filter Imager, which represents
the first scattering polarization observations with sufficient spatial
resolution to discern the granulation. Hinode-SOT offers unprecedented spatial
resolution in combination with high polarimetric sensitivity. The CN band is
known to have a significant scattering polarization signal, and is sensitive to
the Hanle effect. We extend the instrumental polarization calibration routine
to the observing wavelength, and correct for various systematic effects. The
scattering polarization for granules (i.e., regions brighter than the median
intensity of non-magnetic pixels) is significantly larger than for
intergranules. We derive that the intergranules (i.e., the remaining
non-magnetic pixels) exhibit (9.8 \pm 3.0)% less scattering polarization for
0.2<u<0.3, although systematic effects cannot be completely excluded. These
observations constrain MHD models in combination with (polarized) radiative
transfer in terms of CN band line formation, radiation anisotropy, and magnetic
fields.
