Cap'n Nick wrote:God can use people of any profession for his work, and he generally has a better time using people in completely secular jobs that live morally and have zeal for what they're doing than people who make sacrifices in "Godly" jobs that they're not ready in their hearts to make.
This.
I struggled with the same thing a couple years ago regarding my anime loving and passion for writing. All that went down when I was in China and by the time I came back I was fairly certain that God wanted me to write what I'm loosely calling "Christian anime stories." What happened was I sat in bed one night and decided to dedicate my writing to God and since then the story ideas I've gotten have smoothly blended Christianity or a Christian worldview and fantasy/anime elements without compromising either. Yeah, there are some fantasy elements I don't use but I don't feel like I want to use them and then can't, so I really don't see my writing as stuck in a box.
The point of that little story was that maybe you should try giving up your film making to God and see what happens. He gave you that creativity and that passion for a reason and He probably has some way that He wants you to use it. God doesn't give people passions for no reason, although it's very easy to take those passions on the wrong path. For example, I used to be very prideful about my writing, though I didn't outwardly show it, and I thought it was honoring God when it really wasn't.
Helping the homeless is an amazing experience. Often times, I feel that they help me more than I help them. There are some very intelligent and spiritual people out on the streets that everyone should take the time to listen to. I don't thinking looking at film making and helping the homeless should really be a one or the other type of thing. You can very easily do both. The group I go with at school goes on Thursday nights (which I miss because of swing dancing) and Saturday mornings. You could spend a couple hours with the homeless on weekends or whatever and still make films.
All in all, take it to God and He'll make things clear for you, even if he shows you the way over 9,000 times and you still ask Him, XD.