SlingStudio does not support 4K video directly; the highest video resolution that it works with internally is 1080p.
However, you can still use 4K video with SlingStudio productions that you import into Apple Final Cut Pro X. That's because the SlingStudio Converter for Final Cut Pro X supports a 4K video "swap out" technology. It works this way:
What do you need?
Note: The SlingStudio Converter for Apple Final Cut Pro X runs as an independent application. It is best to convert your SlingStudio project to Apple Final Cut Pro X format before launching the Apple Final Cut Pro X application.
Important to reiterate: