The VIRMOS deep imaging survey -: II:: CFH12K BVRI optical data for the 0226-04 deep field

In this paper we describe in detail the reduction, preparation and reliability of the photometric catalogues which comprise the CFH12K-VIRMOS deep field. This region, consisting of four contiguous pointings of the CFH12K wide-field mosaic camera, covers a total area of 1.2 deg(2). The survey reaches a limiting magnitude of B-AB similar to 26.5, V-AB similar to 26.2, R-AB similar to 25.9 and I-AB similar to 25.0 (corresponding to the point at which our recovery rate for simulated point-like sources sources falls below 50%). In total the survey contains 90 729 extended sources in the magnitude range 18.0 < I-AB < 24.0. We demonstrate our catalogues are free from systematic biases and are complete and reliable down these limits. By comparing our galaxy number counts to previous wide-field CCD surveys, we estimate that the upper limit on bin-to-bin systematic photometric errors for the I-limited sample is similar to10% in this magnitude range. We estimate that 68% of the catalogues sources have absolute per co-ordinate astrometric uncertainties less than \Deltaalpha\ similar to 0.38 and \Deltadelta\ similar to 0.32. Our internal (filter-to-filter) per co-ordinate astrometric uncertainties are \Deltaalpha\ similar to0.08 and \Deltadelta\ similar to 0.08. We quantify the completeness of our survey in the joint space defined by object total magnitude and peak surface brightness. We also demonstrate that no significant positional incompleteness effects are present in our catalogues to I-AB < 24.0. Finally, we present numerous comparisons between our catalogues and published literature data: galaxy and star counts, galaxy and stellar colours, and the clustering of both point-like and extended populations. In all cases our measurements are in excellent agreement with literature data to I-AB < 24.0. This combination of depth and areal coverage makes this multi-colour catalogue a solid foundation to select galaxies for follow-up spectroscopy with VIMOS on the ESO-VLT and a unique database to study the formation and evolution of the faint galaxy population to z similar to 1 and beyond.