Prompt photon production in pA collisions has
long been suggested as a sensitive probe of
the nuclear parton distribution functions (nPDFs).
In this study, we present recent results on another
cold nuclear matter effect, namely
fully coherent radiation induced by parton multiple scattering,
which may influence the nuclear dependence of prompt photon production.
Medium-induced radiation effects,
implemented in leading-order direct and fragmentation photon processes,
are computed for pPb collisions at the LHC.
At backward rapidity,
photons are sensitive to fully coherent energy loss (FCEL),
while at forward rapidity,
fully coherent energy gain (FCEG) plays a crucial role
due to the dominance of
the $qg \to q\gamma$ scattering channel.
In contrast, for virtual photon production, the impact
of fully coherent radiation is marginal,
making Drell-Yan (DY) one of the best ways to probe nuclear PDFs.
The power of the DY process is demonstrated by reweighting
nPDF sets at next-to-leading order
using realistic pseudo-data for LHC Run 3.