I don't get it.
I've watched two series of The Killing, The Bridge, Borgen and Follow the Money (all Danish or Swedish/Danish series with English subtitles). I understood what people said and everything that happened. That's many hours of comprehensible input. Great TV too.
And yet... I cannot understand any Danish (apart from the the odd swear word). I occasionally repeat things to amuse myself and my wife, but I can barely say a word. Comprehensible input failed miserably.
This is not really to dismiss CI, of course, but just a reminder that understanding language with the aid of subtitles is an inefficient way of learning a language. It's also a reminder to teachers that showing a film in the target language to near beginners or low intermediate pupils does little to directly further acquisition. It may serve other very useful purposes, such as giving an insight into culture and contributing to general motivation, but it's a very inefficient way to teach a language to inexperienced learners.
If you want to use film with new linguists you might have a look at Sara-E Cottrell's blog post about scaffolding Spanish film for 'Novice-Mid' students (the ACTFL's term).
She describes her approach thus:
"It is a bridge between the aural input and the oral output, a middle piece in that continuum where on one end they’re passively listening to comprehensible input and on the other end they’re accomplishing a performance task in the target language."
You can read her blog for more detail.
If you want whole films to seriously help with acquisition it generally makes sense to begin with high intermediate students who have acquired enough language to be able to begin to decipher the rapid stream of language they hear. Even then, I would choose films in which characters speak clearly and relatively slowly, preferably with pauses which allow students to process what they have heard. This is when comprehensible input can have its effect.
So with subtitles input can be comprehensible, but not usefully comprehensible. As strong proponents of CI rightly say, input needs to be at the student's level, or just above it. This is common sense.
For lots of ideas on how to exploit film with advanced students you might find this useful: