The point spread function (PSF) is a function of off-axis angle and photon energy for all X-ray cameras. The correct calculation of this value is time consuming. In practise, the XMM-Newton EPIC cameras have been designed to minimise the variation of the PSF, and hence the encircled energy fraction (EEF), across the field of view and across the range of observed photon energies. For this reason, a good approximation to the EEF, for fixed radii, can be tabulated within the code for each camera. The tabulated values, used within the program, are shown below but may be overridden on the command line. They should be accurate to about 5%.
| Extraction radius | Camera | |||
| (arcsec) | MOS-1 | MOS2 | EPN pointed | EPN slew |
| 15 | 0.68 | 0.69 | 0.71 | 0.65 |
| 30 | 0.83 | 0.83 | 0.88 | 0.85 |
| 45 | 0.89 | 0.89 | 0.93 | 0.91 |
| 60 | 0.92 | 0.93 | 0.95 | 0.94 |
