Radial-velocity shifts of synthetic isolated Fe I lines at λ620 nm in the N58 model. Relations between shifts at solar disk center, μ = 1, for weak, medium, and strong lines are shown for different excitation potentials. Each point represents one temporal snapshot during the simulation. The dotted reference lines give the identity relations; the other fitted lines indicate how the dependence of convective blueshift on line strength and excitation potential generally remains valid, even when the spatially averaged radial velocity fluctuates.