From left to right: maps of the intensity derivative , and of the P and V signals calculated with different spatial resolution in the blue wing of the Si I 10 827 Å line at wavelengths where the modulus of the intensity derivative is maximum. Top: original spatial resolution (no smearing effects). Middle: finite spatial resolution due to the light diffraction on a 4 m telescope. Bottom: surface variations of the Stokes signals affected by the finite spatial resolution of this telescope and seeing effects corresponding to the Fried parameter R₀ = 50 cm. The lower and upper limits of the Stokes signals are indicated at the right side of the images. The solid curves mark the boundary of granules. The maps were calculated using the 3D model of Rempel (2014) discussed in Sect. 2.1.