For historical reasons, it is useful to offer comparisons between the current WFPC2, and its predecessor WF/PC-1, which was returned to Earth in December 1993. Field format: WF/PC-1 contained 8 cameras and CCDs, each CCD having 800 x 800 pixels. ... Many differences derive from the fact that the WF/PC-1 CCDs were thinned, backside illuminated devices whereas the WFPC2 CCDs are thick, frontside illuminated devices. ... WFPC2 devices have much less CTE error, and hence no preflash is used. ...