DP Mitch Martinez has been shooting 4K for quite some time, and he's made tons of clips free to download.

He's been shooting on cameras like the RED EPIC DRAGON, RED EPIC MX, and RED ONE MX, and with so many extra 4K clips, he decided to release them for free online as stock footage, even for commercial projects. If it's a commercial project, he just asks that you fill out a release form. Here's more on this, thanks to Nino over at cinema5D:

The overall goal is to help the film community by sharing my footage with the world. It evolved really organically – starting with just two clips of fire that I uploaded to my website in January 2013 and shared with my Facebook friends. After time, Google search results led more and more people to my website so I needed to develop official license agreements due to the volume of clips and number of users. Originally, each release form I issued was created manually in Microsoft Word to create the pdf, so it wasn’t long before I needed software development to help generate approved release forms for users. A year ago, it would take me five or six minutes to issue one license agreement manually; now I can approve a license agreement and send it to the user in a matter of seconds.

All of the clips are available for free in the MP4 file format, but if you want higher quality ProRes, original R3D RAW files, or DPX files (or anything else), those won't be free. Some of the individual ProRes files are $45 for 4K or $30 for 1080p, but there are discounts for larger bundles, and he will also make custom bundles for you depending on what you need. Check out some examples of the footage he has to offer:

Here are the categories to choose from when selecting clips:

And if you're wondering, yes his footage has been used in major commercial projects. As PetaPixel pointed out, his footage has appeared in both Sin City: A Dame to Kill For and in The Hunger Games: Mockingjay Part I. The first film used a fireworks clip from Mitch and the second used clouds and tall weeds, as well as the fireball at the end:

To see what Mitch has to offer, or to download some clips, head on over to his site here.