... arfgen (arfgen-1.66.4) [xmmsas_20050815_1803-6.5.0] . ... In practice, arfgen does not use the input detector map 'as is'; instead it uses a filtered form of the detector map in which the points that lie outside the regions used to accumulate the input spectrum are excluded. ... In this case the number of image map pixels should be correspondingly greater to ensure a good coverage over the region of interest, which will result in a performance overhead during the initial filtering process. ...