f is {TAIL ~ the focal length} of {HEAD ~ the taking lens} of the photographic film package, 
f is { TAIL ~ the focal length } of { HEAD ~ the taking lens } of the photographic film package ,
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH