  Measurements are presented and analyzed of the strength of the Ca II triplet
lines in red giants in Galactic globular and open clusters, and in a sample of
red giants in the LMC disk that have significantly different [Ca/Fe] abundance
ratios to the Galactic objects. The Galactic objects are used to generate a
calibration between Ca II triplet line strength and [Fe/H], which is then used
to estimate [Fe/H]_CaT for the LMC stars. The values are then compared with the
[Fe/H]_spec determinations from high dispersion spectroscopy. After allowance
for a small systematic offset the two abundance determinations are in excellent
agreement. Further, as found in earlier studies, e.g., Battaglia et al. (2008),
the difference is only a very weak function of the [Ca/Fe] ratio. For example,
changing [Ca/Fe] from +0.3 to -0.2 causes the Ca II based abundance to
underestimate [Fe/H]_spec by only ~0.15 dex, assuming a Galactic calibration.
Consequently, the Ca II triplet approach to metallicity determinations can be
used without significant bias to study stellar systems that have substantially
different chemical evolution histories.
