Apple’s new iPhones, the 6s and 6s Plus, sport significant camera upgrades, including 12-megapixel iSight cameras, 5-megapixel FaceTime cameras complete with a new Retina flash feature for better selfies, and a new Live Photos function that turns your still images into mini movies.

The other major improvement Apple made to this year’s iPhone camera is the ability to shoot videos in 4K quality. That means the iPhone 6s and 6s Plus can shoot video at 2160p HD resolution compared to just 1080p HD on an iPhone 6 and 6 Plus.

Since 4K video is storage-hungry (see below), the feature is not automatically enabled in the iPhone’s camera app. Instead, the default setting records video at 1080p HD at 30 frames per second (fps).

Below we show you how to enable 4K video recording, look at how much storage your 4K clips will gobble up, and show you an example of what quality to expect from a 4K video.

How to enable 4K video recording on iPhone 6s, 6s Plus

1. Launch the Settings app.
2. Tap on Photo & Camera.
3. Under the Camera section, tap on Record Video.
4. The default 1080p HD at 30 fps is ticked. Below that, tap on 4K at 30 fps.

You also have the option to select 720p HD at 30 fps or 1080p HD at 60 fps.

How much storage does a 4K video use on iPhone 6s, 6s Plus?

Recording a one-minute 4K video can gobble up nearly 400MB of storage or nearly twice as much as the same video shot at 1080p HD. Not an ideal situation if you’re using a 16GB iPhone or have a ton of apps, media, and other junk saved on your iPhone.

Apple provides the following guidelines for storage requirements for a minute of video shot at various resolutions:

• 720p HD at 30 fps: 30MB
• 1080p HD at 30 fps: 130MB
• 1080p HD at 60 fps: 200MB
• 4K: 375MB

How to easily spot which resolution your iPhone is set to record in

Launch the Camera app > select video mode > look for a small white box showing the current resolution to the right (in portrait mode) or above (in landscape mode) the shutter button.

If the default resolution of 1080p HD at 30 fps is enabled, nothing will show here.

What’s the difference between 4K and 1080p HD?

At a resolution of 2160 x 3820, 4K has four times more pixels than 1080p HD with a resolution of 1080 x 1920.

What does that look like? Dom Esposito at 9to5Mac shared a video demonstrating 4K footage shot with an iPhone 6s. You’ll see the best results if you view the video on a 4K capable screen.

For more 4K footage shot on iPhone 6s and 6s Plus, check out Apple’s own video showcase.

Screenshot via Apple