There are basically two ways of soliciting donations for this type of project. 1) large donations from a small group of people or organizations, or 2) small donations from a large group of people or organizations.
If two people give you $1000.00, or if 2000 people give you $1, you still have $2000.00. Both ways are equally difficult, but pick one and stick with it.
Either way you choose, some advice:
1) Sell the cause, not the project. It will be easier to solicit money to "help raise homeless awareness" than it will to "buy a new camera".
2) Unless you have a good lawyer, offer nothing in return but a receipt. Charitable contributions are tax deductible. You can get a receipt book at Staples for $4 or less. Do NOT offer them any kind of compensation! Investments (even small ones) are heavily regulated by the SEC and even just TALKING to someone about a personal gain they can make (points, ROI, percentage ownership, distribution rights, etc.) can land you in hot water. The laws are all heavily in favor of protecting naive investors from unscrupulous scheisters.
3) Look for a sponsorship from a related organization, like a homeless shelter or a church that operates a soup kitchen. Don't ask them for money, obviously, but they can help you get the word out about your project and provide you with contacts that can prove valuable, and in exchange you can use their name to lend legitimacy to your project. "We're working in conjunction with the 6th Street Helping Hands Shelter to raise awareness... etc etc".
4) Have a budget and a plan. What is your film going to accomplish? How much is it going to cost you to get it made? Not everyone will want this information, but being organized and having this information ready when asked (a one page sheet with bullet points is fine) will go a long way to convince others that you're legit and capable. Guestimate the numbers as best you can, and err on the conservative side. Try to say something like "the film will cost $5000.00 to make, but it will eventually provide enough contributions to local shelters and organizations that could mean as many as 300 new beds, 650 new hot meals served each week, and 400 extra hours a month of personal employment and life management counseling services to help get an estimated 150 people off the street."
Now, I realize it's been a month since you posted this, but I suppose there's a chance it will do you (or someone else) some good.
"We're trying to raise money to get a camera so we can make an important film about homelessness on Skid Row."
...is not nearly as persuasive as...
"Malachi Films is working with the Los Angeles Homeless Services Coalition to make an important film raising awareness of the growing problem of homelessness in the Skid Row area of Los Angeles. Hundreds of people - men, women, and even children - are without the basic necessities we take for granted. They spend each and every day struggling to find food, shelter, clothing, and medical care. There are individuals capable of helping these people, but those individuals are drastically out of touch as to the extent of the problem. We're making this film because these people are in extreme and immediate need of help, and we hope that, when finished, our film will help provide them with hot meals, clean clothes, additional beds to sleep in, and the personal counseling services they need to get back on track, find jobs, and create a better life for themselves. This film is being produced entirely Not-For-Profit, and your tax deductible donation of whatever you can spare - $1, $5, or more - has a chance to make a difference in the lives of hundreds of people."
Hope that helps.
-Jeff