Each grey level signal causes {HEAD ~ a particular proportion} of {TAIL ~ pixels} to be illuminated, in order to produce a particular grey level 
of
Each grey level signal causes { HEAD ~ a particular proportion } of { TAIL ~ pixels } to be illuminated , in order to produce a particular grey level
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH