Comment by apognwsi

that's not right. if photons were truly spin 1, there would be 3 spin eigenstates available, but in fact there are only 2 (Sz=0 is unavailable). the pithy argument invokes the absence of a stationary frame of reference. for all practical purposes, photons are behave like spin 1/2 particles (despite being bosons). see, for example, the jones algebra / calculus.