The online lab I've been using (happily) is Mpix. Their instructions for submitting non-standard aspect ratio images is to “place them on a canvas in Photoshop” and size to the next highest size. Basically, creating a border around the image to allow the “canvas” to match a standard print size. I'm holding out against purchasing PhotoShop (Aperture does 95% of what I need and $700 is a lot to spend on software). Questions: Is there a way to create the “larger canvas” that is required using Aperture?
The ATEM Mini is a powerful device on its own, but once you start writing macros for it, hoo-boy… you can make this thing sing!