Top row: colour − magnitude diagrams for all objects (dots) in HCG 22 for each of the four WFPC2 pointings. The legend for each CMD indicates the galaxy/region at which the WF3 chip was centred. Bottom row: colour − colour diagrams of all sources (dots) with photometry for the same fields. In all panels the open circles indicate the objects with spectroscopy while the open squares are the UCD candidates. The description of the SSP isometallicity tracks is the same as in Fig. 5.