I understand from some of your previous Q&A's here on Yahoo!Answers that you are a young Canadian writer who aspires to direct films, and who enjoys directors like Stanley Kubrick & Ridley Scott ("Barry Lyndon" & "Blade Runner", respectively).
Now, you are focused on renting a 16mm film camera & spending a $20,000 budget on a scripted short film. But in the last couple of months, you've been asking such basic questions such as "How do you edit a film made in film?" and "How does sound work?"
This is why people go to film school. But you "Do not plan on goin' to film school."
I'm afraid you'd end up spending $20K, having no useable film to show, and getting your own expensive version of "school-of-hard-knocks" film school.
As for your actual Question, traditionally the D.P. (director of photography), not the film's Director, decides the camera & which lenses to use for shooting. The Producer, not the film's Director, makes the rental arrangements and pays the bills.
On a small independent production, the Producer & Director (and even D.P.) can be the same person. But you are an aspiring director with no experience on-set or behind a camera.
If you have an actual "finished script", you should first try to get it "workshopped" at a local drama group or university drama department. This is the best way to see how all your scenes play out with real actors (and not spend a dime on film & lab costs). This will also introduce you to talented actors you can afford later on.
The Sundance Institute (Robert Redford's non-profit organization which also produces the Sundance Film Festival) has various Labs/workshops & Fellowships to allow new writers & other creative people to collaborate without going broke.
Canada has its famous National Film Board, which has supported dramatic & documentary artists, based in Montreal. Sadly, budget cuts this past fall has caused the closing of NFB's "public access" studio facilities (which alleviated the need for rental equipment). But this is still a financial avenue you should explore for grant money.
YouTube's partnership with places like Maker Studios has allowed other talented people access to facilities and crews (and actors) without the overhead a regular production would cost. Take a peek at their promo reel: http://www.makerstudios.com/
You should explore some of these avenues, and read a book or two on filmmaking & film editing, and how to make a realistic production budget. Visit some local colleges that have a film or video production department (visit with a professor or Department Head over coffee), and make use of their library resources for in-depth knowledge.
And get over your apparent prejudice over video technology & computer editing (most "films" use computers now -- I haven't touched a "film splicer" in 30 years!). Computers & "video assist" are cost-effective tools used throughout the movie industry. And I could show you two different "movies" -- one shot on film & one on digital-cinema (video) -- and defy you to guess the difference.
Also consider what has to happen =after= you get a 16mm film short made: for advertising & promo clips you need a video-transfer (telecine), for internet exposure you need a video-transfer, and for DVD copies you need a video-transfer. I don't think you'll be lugging around a 16mm projector every time you want to show off your "film".
hope this helps,