Center-to-limb variation of the convective blueshift of the Fe I 5436.3 Å (panel a), Fe I 5436.6 Å (panel b), and Mn I 5432.6 Å (panel c) line. Each data point represents the mean Doppler velocity of the lower 5% of the bisector of the temporally averaged observation sequence. Error bars indicate the mean error. Radial axes are indicated by colors and symbols. The black solid line and gray shaded area display the average center-to-limb variation and its standard deviation.