Philip Bloom has posted a short video on his website showing his workflow for creating 2:35 video on Vimeo. Definitely worth checking out. I learned a number of things:
Framing in the camera
He says he guesstimates the framing (though he says you can also put tape on the monitor.) - He doesn't do too badly with the framing!
Framing matte in Final Cut Pro
While working with the 1920x1080 footage, he applies Final Cut Pro's Widescreen filter to get a matte showing the actual framing. The Widescreen filter is a simple effect that has a number of choices for different aspect ratios. My problem with this filter (from playing with it a little) is that it builds it's matte based on the dimensions of the material, not the Canvas window. So if you have video with a different aspect ratio, or you make it bigger or smaller than 1920x1080 on the Canvas, then the matte will be wrong.
If you do have that problem, another solution would be to create a .png graphic in Photoshop that has the top and bottom bars, and the middle is transparent, and then place that on the top video track.
If anyone has a better solution (or I'm using the Widescreen filter wrong, let me know!)
Cropping the export in QuickTime Player
Philip exports to a QuickTime movie (reference movie) and then uses QuickTime Player 7 (the old version, not QuickTime X) and after choosing Export, in Options he sets the Image Size to Custom, and enters 1920 x 816. This crops off the top and bottom matte giving you just the content, which is really useful because...
Vimeo supports other Aspect Ratios
This is probably the thing that surprised me the most. I had assumed that Vimeo supports just 16x9, and it would distort any other size that was uploaded. But no, it appears it understands and supports different aspect ratios. If you check out Philip's page, you'll see a clip with a very different aspect ratio, with no top or bottom matte.
So why do it?
Creating movies with this aspect ratio does beg the question; what's the advantage to having the movie stored in the actual aspect ratio rather than putting it in a 16 x 9 file with top and bottom mattes? Particularly given that most computer displays are either 16 x 9 or 4 x 3, so having a movie of a different aspect ratio means you'll have black bars anyway when playing at full screen. So unless you have a wider than standard widescreen monitor, you're not going to derive any real advantage.
Of course, if you want/like that aspect ratio's look, the movies will look cleaner on your web page than if it's in a frame with top and bottom boards. Also, you'll save a little data in compression as the boarder area isn't being compressed; though that probably doesn't take up much space.
And something tells me a lot of people are going to be producing movies in these aspect ratios over the next month or two.
Philip Bloom: How to export and upload 2:35 video to Vimeo