1 INTRODUCTION
2 SAMPLE
2.1 Photometry
2.2 Spectroscopy
2.3 Comparison sample
3 CALCIUM TRIPLET MEASUREMENT
4 ANALYSIS
4.1 Metallicity scales
4.2 Biases
4.3 Repeated Measurements
4.4 Calibration
4.5 Colour–metallicity relation
4.6 Testing bimodality
5 DISCUSSION
5.1 The calcium triplet as a metallicity indicator
5.2 The colour–metallicity relation of globular clusters
5.3 Globular cluster metallicity distributions
5.4 Comparison with previous calcium triplet measurements
6 CONCLUSIONS