[pdonis]

> outside observer will measure clocks of photon run slower by a factor of γ

This is not correct since "clocks of photon" is a meaningless concept (at least if photons have zero mass, which they do according to our best current models).

[Yajirobe]

Obviously, I did not mean to imply that you can attach a clock on a photon. I thought this goes without saying.

[pdonis]

> I did not mean to imply that you can attach a clock on a photon.

The issue isn't that you can't attach a clock to a photon in a practical sense. The issue is that even in principle, the concept of "the clock of a photon" is not well-defined. For it to be well-defined, there would need to be an inertial frame in which a photon was at rest. But that is impossible.