Each light sensor generates a measurable electrical quantity responsive to the associated vignetted light field, and {HEAD ~ the collective measurable electrical quantities} are responsive to {TAIL ~ incoming light field} 
Each light sensor generates a measurable electrical quantity responsive to the associated vignetted light field , and { HEAD ~ the collective measurable electrical quantities } are responsive to { TAIL ~ incoming light field }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL