  We present joint Hinode/EIS and IRIS observations of Fe XII lines in active
regions, both on-disk and off-limb. We use an improved calibration for the EIS
data, and find that the 192.4 A / 1349 A observed ratio is consistent with the
values predicted by CHIANTI and the coronal approximation in quiescent areas,
but not in all active region observations, where the ratio is often lower than
expected by up to a factor of about two. We investigate a number of physical
mechanisms that could affect this ratio, such as opacity and absorption from
cooler material. We find significant opacity in the EIS Fe XII 193 and 195 A
lines, but not in the 192.4 A line, in agreement with previous findings. As we
cannot rule out possible EUV absorption by H, He and He II in the on-disk
observations, we focus on an off-limb observation where such absorption is
minimal. After considering these, as well as possible non-equilibrium effects,
we suggest that the most likely explanation for the observed low Fe XII 192.4 A
/ 1349 A ratio is the presence of non-Maxwellian electron distributions in the
active regions. This is in agreement with previous findings based on EIS and
IRIS observations independently.
