We present deep and precise multiband (U, B, V, I) optical data for the Carina dwarf spheroidal galaxy. Data were collected using three different ground-based telescopes (4-metre Blanco CTIO, MPG/ESO 2.2-metre, 1.5-metre CTIO) and cover the entire body of the galaxy. We discuss the reliability of the absolute photometric zero-point calibrations of images collected with large-format and mosaic CCD cameras. The typical precision for the B- , V- and I-bands is better than 0.01 mag. The U-band is a little worse. A preliminary comparison with scaled-solar and alpha-enhanced evolutionary predictions covering a broad range of ages and chemical compositions seems to support previous photometric evidence that both the old (12 Gyr) and the intermediate-age (4-6 Gyr) subpopulations show a limited spread in chemical composition. The use of the Carina galaxy field as a possible standard stellar field is outlined.