Smart list with 4k content only

Hello,

this is a pretty straight forward question:
How do i create a smart list that will only show me the movies that are in 4k?

I know how to create smart lists, but whatever value I put in the field, I either get all hd content or none of it.
I read somewhere that Kodi only has three predefined areas of resolutions. And it will return the group that the value falls into.
Maybe this info helps to narrow down the problem.

Thanks guys