When a large number of counts are put into a small length of the detector volume, a space charge effect develops which attracts the electron cloud towards that region of the detector. This results in lines that are taller and narrower than they should be and locally distorts the linearity of the detector. This effect is not confined to spectral lines and can occur in any region of the detector where the photon flux is large; the total number of counts is conserved, but there is a loss of positional information. It is not clear that this effect can be deconvolved, and the matter is still being studied. More information is given in Trow, Bento and Smith (1993).