> What's the best way to achieve this?
Cropping, rendering it out in 2:25:1 or using overlay images that are exactly the ratio that you need?
It depends on what, exactly, you're trying to do.
If you're trying to create a movie that is actually 2.35:1, then the best thing to do is to export a movie that has that aspect ratio.
However, if what you're trying to do is make a movie that is 4:3, 16:9, or whatever---but have a 2.35:1 image letterboxed within it---then the best thing to do is use scaling and/or cropping on the image within the 4:3 or 16:9 frame.
So, what exactly are you tryying to accomplish?
I'm trying to render a 16:9 piece of footage into 2:35:1 and was wondering what the best way to do this was.
If you're going out to disk (DVD or Blu-ray), you need to fill the frame. That means using the Crop effect inside of Premiere Pro so that the black bars are part of the image.
If you're going out to a file for computer playback, then you can do the above, or you can Crop it during the export phase, which cuts out the black bars and leaves only the viewable image.
Here's the formula:
1. Take the aspect ratio of the footage you have, say 4:3 or 16:9, and do the math. [4 / 3 = 1.333; 16 / 9 = 1.777; etc.]
2. Divide that by the aspect ratio you want (many people still call it 2.35, but since the early 70's the standard has actually been 2.39). [1.777 / 2.39 = .7438]
3. Multiply that result by 100. [.7438 x 100 = 74.38]
4. You need to see 74.38% of the image to get the desired ratio. The corollary is that you need to crop 25.6% of the image, or 12.8% from top and bottom.