Since I get asked this a lot, I figured I just show you here how I do it. I've shown all the GHearHeads how to do it in AE, but here's how you do it in FCP 7, just go to your sequence settings and conform them to something similar to this.
1920x1080 is 1.77:1
1920x818 is a perfect 2.35:1
1920x1038 is 1.85:1
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