Currently, 16:9 and 4:3 co-exist both as acquisition and final delivery formats. Jude Cotter sets out to give you a basic understanding of the differences between the two and how they can be used together and still be correct, look good, and fulfill your program specifications. 

Using footage of different aspect ratios together on the same timeline has long been possible in the quality editing software suites. If you are lucky you will never have come across the problem, but that would be quite surprising and you know it's going to happen at some point.

In Faking It : Making 4:3 footage work in 16:9 projects, Jude Cotter looks at the problems inherent to mixing aspect ratios, and examines a range of techniques for getting 4:3 to work as 16:9 and vice versa. Now and into the future, the most common need will be to disguise 4:3 footage in a 16:9 project, but 4:3 programmes and DVDs are still a necessity, and an increasing amount of footage is shot as 16:9. Shooting HDV for an SD final product gives you the option of scaling down, cropping or pan and scan, effectively solving the problem of mixing aspect ratios. But that assumes a luxurious workflow and things don't always work out that way.

The article provides a few ideas for when the mixture of footage and the demands of the final output are less than ideal for the editor. Well worth a read if you need a few ideas before starting a mixed aspect ratio project.

http://www.kenstone.net/fcp_homepage/faking_it.html