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