We present [Fe/H] and [Ca/Fe] of ∼ 600 red giant branch (RGB) members of the globular cluster Omega Centauri (ω Cen). We collect medium-resolution (R ∼ 2000) spectra using the Blanco 4 m telescope at the Cerro Tololo Inter-American Observatory equipped with Hydra, the fiber-fed multi-object spectrograph. We demonstrate that blending of stellar light in optical fibers severely limits the accuracy of spectroscopic parameters in the crowded central region of the cluster. When photometric temperatures are taken in the spectroscopic analysis, our kinematically selected cluster members, excluding those that are strongly affected by flux from neighboring stars, include relatively fewer stars at intermediate metallicity ( [Ca/Fe]. We also do not find convincing evidence for a radial metallicity gradient among RGB stars in ω Cen.