The role of the diffuse ionized gas in metallicity calibrations
  Estimates of gas-phase abundances based on strong-line methods have been
calibrated for H~{\scshape ii} regions. Those methods ignore any contribution
from the diffuse ionized gas (DIG), which shows enhanced
collisional-to-recombination line ratios in comparison to H~{\scshape ii}
regions of the same metallicity. Applying strong line methods whilst ignoring
the role of the DIG thus systematically overestimates metallicities. Using
integral field spectroscopy data, we show how to correct for the DIG
contribution and how it biases the mass--metallicity--star formation rate
relation.
