1. An illumination filter ( 36 , 44 ) for an illumination filter system ( 2 ) for medical imaging ( 1 ), in particular multispectral fluorescence imaging, comprising a spatial filter pattern ( 43 ) masking a defined filtering fraction of a first illumination path ( 47 ) on the filter and masking a defined filtering fraction of a second illumination path ( 48 , 49 , 50 ) on the filter, wherein the filtering fraction of the first and the second illumination paths ( 47 , 48 , 49 , 50 ) are different.