UHD 4K videos are not the type of videos you watch everyday. But the Android flagships have already added the option to take 4K videos using the main camera. To record 4K videos on Nexus 6 do as follows:.
1. Open the Camera application on your Motorola Nexus 6
2. Make sure the video recording mode is enabled and then touch the Settings button on the top
3. Tap the Resolution & Quality option
4. Now, under the Video settings, tap the Back camera video option and select the UHD 4K as the video recording quality
** Other quality options to record videos on Nexus 6 are: 1080p HD and 720p HD