  The Clifford spacetime algebraic description of Maxwell's equations is
reviewed and shown to give a unified picture of recently published versions of
photon quantum mechanics. Photon wave equations and a conserved four-current
are derived from the complexified standard Lagrangian. The equations of motion
and scalar product are found to be in good agreement with those obtained from
Fourier transformation of momentum space wave function and scalar product
[Phys. Rev. A 102, 042201 (2020)].
