I started loading at 16, Focus Pulling at 18, Operating at 20, Steadicam at 22, DPing at 23.
Granted I had a father who was a cameraman so had oppotunities early, but it doesnt matter.
It all depends on the oppotunities you get and obviousley not moving up before you think you are ready to do so. I got lucky and started working with a good group of people who were all fantastic at what they did and were moving up through the positions whilst at film school. So I simply went with them and learnt the hard way as we went along.
Another good way of learning and seeing how it all works is working as a Video Split Operator / Video Asist Operator. I found it a fantastic way to learn, because you get to speek to Directors, Continuity, AD's and of course your Camera Department. Filling in for the loader when he/she is off set etc is great. I operated split on a Spike Jonez movie last year (on the minitures unit) and had a fantstic time because I had more time to ask questions (when appropriate of course) and observe alot more of what was going on and see how it was all working in that bigger scale (production) environment.
Now at 23, Im shooting a fair bit of video, Operating Steadicam on what ever comes my way and Focus Pulling / Loading as my in and out day job. I must say that I am a bit picky about some of the jobs that come my way. Especially when it comes to Focus Pulling and Steadicam operating. In these cases it will all depend on the DOP and wether I think I am ready and prepaired to do the job or not.
At the end of the day, its all about knowing the gear, processes, procedures and going from there.
Age has nothing to do with it most of the time. Just dont stuff it up!!
JP
Melbourne Australia