A globular cluster is an admirable object for the study of stellar evolution and theoretical investigations of the isochrones in the colour-magnitude diagram (CMD) have been numerous, with the most recent being that of Vandenberg (1983, Ap. J. Suppl. 51, 29), but there are still uncertainties such as rotation, abundance variations and gravitational settling. The matching observations are in fair agreement. However only a small number of clusters have been observed and the detailed matching is poor. Most of the CMDs are from photoelectrically calibrated photographic photometry which are affected by the variable background found in clusters. Modern detectors suffer less from this problem and are very sensitive. A programme has been underway on a number of clusters using electronographs and CCDs with the SAAO 1.Om telescope and the crowded-field Starlink Aspic software. This paper reports on preliminary results from four of the clusters. The CCD observations were done in collaboration with W.K. Griffiths of Leeds University.