When the film 32 is completely unwound from its spool 34, the amount of back tension in the length of film which runs from the take up reel 52 to the film cassette 30 increases greatly due to the fact that the end of the film 32 is still attached to {HEAD ~ the spool} 34 within {TAIL ~ the film cassette} 30 
When the film 32 is completely unwound from its spool 34 , the amount of back tension in the length of film which runs from the take up reel 52 to the film cassette 30 increases greatly due to the fact that the end of the film 32 is still attached to { HEAD ~ the spool } 34 within { TAIL ~ the film cassette } 30
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH