The user selects {HEAD ~ maximum gain} to cause {TAIL ~ a scene} to go dark at a certain low light level rather than gaining up to a noisy image 
to cause
The user selects { HEAD ~ maximum gain } to cause { TAIL ~ a scene } to go dark at a certain low light level rather than gaining up to a noisy image
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH