aperture 74 is seen to be formed as a substantially sinusoidal curve 76 with portions of the curve 76 acting as intrusions into the aperture 74 it is to be understood that the curve 76 could take other than a sinusoidal form referring now to fig8 a forward edge 78 of an aperture 80 is seen to be formed arcuately at 82 the edge 78 extending into the aperture 80 to provide the advantages herein described the inverse shape of the edge 78 also functions to produce the performance described herein now considering fig9 it is to be understood that an intrusion into an aperture similar to the aperture 36 shown in fig4 is caused to occur essentially at central portions of an aperture a forward edge 84 of an aperture 86 as seen in fig9 being formed along central portions thereof as a wedge 88 the wedge 88 extending from portions of the edge 84 near central portions thereof rather than tapering from ends thereof as occurs with the wedge 48 of the forward edge 40 shown in fig1 through 4 intrusions into apertures of luminaires as contemplated by the invention can thus be seen to be most efficiently provided along centrally disposed portions of forward edges of said apertures whether such intrusions take the form of wedges teeth arcuate elements or the like the inverse shape of the edge 84 also.