Well, the localization effects the probability density of a photon. The shorter the wavelength, the more localized, the higher the wavelength, the less localized. But, how do we actually know the wavelength before we measure it? If a source emits a photon, the wavelength is unknown, so how is it's localization already determined? Furthermore, would this imply that if I move away from a gamma-ray photon at 99% the speed of light, I would measure it was a radio wave but it would still have a small localization before I measured it?