The arrival of 4K video means that an increasing number of devices are effectively capturing prolonged bursts of 8MP images at fast frame rates, increasing the likelihood of capturing 'the moment.'

Using a video feed to capture stills isn't a new idea - Nikon's first electronic camera, the QV-1000C, did it in the late 1980s - but the resolution of 4K makes it more useful. Panasonic has recognized this way of working and has introduced 4K Photo mode to its 4K cameras, to make things easier for the user.

Panasonics such as the GH4, LX100 and G7 - along with some of their rivals - already make it possible to grab stills from their existing video, but the 4K Photo mode offers some additional tools to make the experience easier.

To understand why it needs its own mode, it's worth considering two potential drawbacks of just trying to take stills from existing video footage. Firstly, the shutter speeds that give the best looking video are the ones that include some subject blur to give a smoother look to movement: the opposite of what you usually want in a still image. Secondly, the wide aspect ratios used for video (16:9 and 1.85:1) aren't always the ones most people would choose for stills capture.

4K Photo mode lets your camera shoot 8MP files at 30 frames per second, and provides some tools to help you find your way back to the best frame. Photo by Sam Spencer

4K Photo mode addresses both of these problems by allowing you to shoot in roughly 4K in whichever aspect ratio you prefer while maintaining the exposure line used in stills mode. It also changes other aspects of camera behavior, such as using full-speed autofocus, rather than slowing it down to give smooth mid-movie transitions, and allowing you to add markers throughout the video to make it easier to find the key moments that you wanted to capture in all the footage you grabbed.

Of course these changes come at the cost of good video. The 4K Photo mode is designed to make it easier to use the 4K capability for stills - it doesn't do anything to relieve the tensions between shooting for video and shooting for stills.

The behavior of the mode changes a little between cameras: on the LX100 and FZ1000, 4K Photo mode simply allows you to shoot non-16:9 4K footage and use the Fn2 button to leave markers throughout the video. The version of 4K Photo on the GH4 also adds the option of loop recording - constantly recording 2 minute chunks of video and deleting anything older than ~10 minutes, to stop you running out of card space, just before the key moment occurs.

The Panasonic Lumix DMC-G7 gets the most sophisticated implementation of 4K Photo yet - to the point that it now gets its own position on the drive mode dial.

The more recent G7 has the most sophisticated implementation, offering three operating modes. Burst mode grabs a section of footage while the shutter is held down, Burst (S/S) starts and stops when you press the shutter button and Pre-Burst constantly records, then saves the 30 frames before and after the shutter is pressed. The final option drains the battery faster than usual, since it's always recording, but offers the experience most like shooting conventional stills - since you continue to try to anticipate the key moment.

The final bonus of 4K Photo mode is that the camera is able to generate full EXIF information for the resulting image. Selecting an image is simply a case of pausing the video and pressing the 'OK' button in playback mode. You can advance frame-by-frame while the camera's paused, which starts to reveal the value of being able to put markers into the video as you capture it - at 30 frames per second, you'll have 15 shots to scroll back through if it took you half a second to hit pause after playback passes the key moment.

What's it good for?

The obvious use of 4K Photo mode is the ability to capture fast-moving subjects. The camera is happy to use fast shutter speeds and will do its best to stay in focus - meaning you effectively have a 25 or 30 frame-per-second continuous shooting mode (Users with PAL-region cameras will have good reason to feel aggrieved at being restricted to 25fps when NTSC users are getting 30fps from the same hardware).

It can also act as something of a safety net if you're trying a type of shooting, such as panning, that you're not too experienced with.

Capturing the right moment in an eighteen person group shot isn't easy. 4K Photo mode makes it a lot easier, though, with nine children involved, it can't perform miracles. Photo by Wenmei Hill

However, fast-moving action isn't the only reason to want to have captured more than one moment in time. Leaving the camera running for a couple of seconds when taking pictures of people gives you more moments to choose from. It means you don't have to perfectly time the shutter as your subject relaxes their facial expression or breaks into a smile, and allows you to choose the moment where nobody in a group shot has their eyes closed.

The use of electronic shutter means that the results of 4K photo can inherit some odd glitches from the nature of a rolling shutter.

The 4K Photo mode isn't a panacea for capturing the moment, though. Because it stems from video, the cameras use electronic shutters. This can result in still images that show the effect of rolling shutter, with vertical elements rendered as diagonal lines if there's rapid movement. This isn't always a problem, since that electronic shutter can work so quickly that very little movement has occurred during the exposure, but ironically is most likely to appear with the kinds fast-moving action that make 30fps shooting seem so attractive. As can be seen in the lightning shot above: 4K Photo doesn't work for every shooting situation.

However, extreme cases aside, 4K Photo mode does a good job of turning high resolution video capability into a useful continuous shooting mode. We wouldn't consider it to be essential for stills-from-video work, but it's a useful set of features that makes the process easier and it's nice to see the subtle improvements Panasonic is making, generation-to-generation.