How does the expansion of the universe affect redshift?

[edoarad]

does the expansion itself redshifts photons (if so, does the expansion affect the photon in his frame of referance?) or is it because the distant object that emits them is seemingly moving away from us (in cases where the expansion is much more dominant of course)? The latter doesn't makes much sense to me because the object isn't really moving as fast as he seems.

 

[Chalnoth]

does the expansion itself redshifts photons (if so, does the expansion affect the photon in his frame of referance?) or is it because the distant object that emits them is seemingly moving away from us (in cases where the expansion is much more dominant of course)? The latter doesn't makes much sense to me because the object isn't really moving as fast as he seems.

Yes, the expansion itself redshifts photons. Basically, the wavelength of photons is increased by the same factor as the distances between galaxies is increased with expansion.