What is 4K resolution? Every question answered

What is 4K video resolution and how will it change the way you shoot still images? We explain everything you need to know about the new standard in video recording and display.

Whether you use the video function of your camera or not, 4K video is a big deal. With four times the resolution of Full HD, it offers more detailed videos and greater scope for post-production effects – and it also opens up the opportunity for extracting high-resolution stills from your movies.

Two recognised 4K video standards currently exist in the camera market: Digital Cinema Initiatives 4K (also known as DCI 4K or Cinema 4K) and Ultra HD.

The former offers a slightly increased vertical resolution, although not all cameras can record in this format. Ultra HD has been more widely adopted, as it matches the 16:9 aspect ratio of widescreen displays and televisions.

To view 4K content, you’ll need a 4K television or compatible display. Don’t have a 4K TV? No problem: the good news is that 4K input doesn’t have to mean 4K output.

You can watch 4K video on a 1080p screen, as long as it has been converted to the lower resolution. ‘Downscaling’ in this way produces a crisper, cleaner Full HD image.

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But it’s the opportunity to capture stills from 4K footage that we’re really interested in. Creating digital images in this way is nothing new, but each frame of 4K video is 3,840×2,160 pixels – generating an 8.3MP image. By comparison, stills extracted from Full HD clips deliver images closer to 2MP.

Of greater significance is that these 8.3MP pictures are captured at up to 30 frames per second. Being able to choose a single, 8-megapixel frame from an entire sequence gives you the flexibility to isolate the ‘decisive moment’ at your leisure.

Sounds ideal, doesn’t it? But the optimum shutter speeds for recording smooth video are generally much slower than when taking photos. This can result in moving objects being blurred in the extracted frame.

The other downside is that the image will be saved in the 16:9 aspect ratio. Cropping to a more photo-friendly 3:2 or 4:3 means losing some of the picture area and reducing the possible print size.

Keen to get around these problems, Panasonic has introduced a 4K Photo mode in its new cameras, with optimised settings for still image capture.

Meanwhile, professional broadcast video cameras are now starting to offer 8K – offering four times the resolution of 4k – and 33.2 megapixel stills from each frame!

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What is 4K resolution?

Standard (640×480)
Standard Definition has a much lower resolution than 4K but offers a vastly reduced file size, making it suitable for everything from YouTube streaming to DVDs. Standard VGA resolution is 640×480 in a 4:3 aspect ratio, while DVD tops out at 720×480 (for NTSC regions) and 720×576 (PAL regions).

HD (1,280×720)
The High Definition format provides 720 lines of vertical resolution and an aspect ratio of 16:9. Now largely replaced by 1080p, digital cameras still offer 720p recording. It’s often the only option for capturing 60fps footage (for slow-motion playback) at HD quality.

Full HD (1,920×1,080)
Two standards exist: 1080i (interlaced) and 1080p (progressive). Both offer 1,080 lines of vertical resolution and an aspect ratio of 16:9. The difference is in how the picture is captured and displayed: progressive (as used by BluRay) gives a smoother image, and is commonly referred to as Full HD.

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4K UHD (3,840×2,160)
Unlike High Definition and Full HD, which are known by their vertical resolution (720 and 1080 pixels, respectively), 4K refers to the horizontal resolution, which is in the region of 4,000 pixels.

4k formats 
There are several industry-recognised 4K resolutions, but the two formats that are now most widely adopted are  Ultra HD (3,840×2,160 pixels) and Cinema 4K  (4,096×2,160).

Screen ratio
The 16:9 aspect ratio of the ‘consumer’ Ultra HD format fits the proportions of most widescreen displays. Cinema 4K’s 1.85:1 aspect ratio is more suited to theatrical display.

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What are the advantages of 4K video?

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Although 4K video is set to be the new broadcast standard, few of us have yet invested in a 4K-ready TV. That means, initially at least, the majority of us will be watching 4K content that’s been reduced in resolution to work with a Full HD display. However, downsampling a 4K image in this way opens up a range of creative advantages when you’re editing a movie.

With four times the area offered by 1080p, film-makers are able to carry out considerable cropping while still retaining enough resolution to produce a crisp Full HD image.

This has obvious benefits for the likes of wildlife films, where getting physically closer to the subject in the field may be impractical or impossible. It also opens up the possibilities for post-shoot zoom, pan and tilt effects.

The downside to recording such large, detailed files is the drain on storage and workflow it creates. You’ll need to factor this in when looking to go 4K…

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Key 4K video options

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Zebra pattern
This useful feature acts like a highlight warning, displaying a striped pattern on any areas that are at risk of being rendered too bright, so you can make exposure adjustments on the fly.

Clean HDMI
Cameras that offer ‘clean’ HDMI output enable you to view and record 4K footage to an external device, without any of the menus and overlays you can see on the Live View screen.

Focus peaking
Manually focusing while recording video is the only option on some cameras, but focus peaking, which highlights areas that are in focus in the Live View display or EVF, makes it much easier.

Recording device
Some cameras are capable of recording 4K footage internally to a large, fast memory card, but others can only stream it to an external recording device, such as the Atomos Shogun, shown here.

Sound
Built-in mics are prone to picking up operational noise. A mic port enables you to connect an external microphone for high-quality audio, while a headphone port lets you monitor it.

Monitor
Vari-angle screens make it more comfortable to record video, allowing you to capture footage from low or high angles without having to get into an awkward position.

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How to use 4K video for stills

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Creating still images from video is straightforward: play a clip on your computer, pause it and take a screen grab or use Photoshop to create an 8MP still.

Panasonic’s 4K Photo mode, introduced on the LX100 and found on the GH4 and GX8 and other recent Lumix models, goes a step further, offering a trio of dedicated options that are optimised for capturing 4K stills.

They can be used in any exposure mode and you can choose the aspect ratio for your images (in 4K Burst Shooting and 4K Burst (S/S)). You’re still essentially recording video, but you can extract the images in-camera.

4K Burst Shooting
Records 8MP images at 30 frames per second for up to 29 mins 59 seconds.

4K pre-burst
This Panasonic option records 8MP images at 30fps for one second before and one second after you pressed the shutter. The result? 60 frames covering a two-second period.

4KBurst (Start/Stop)
This Panasonic mode requires two presses of the shutter release: one to start recording, and another to end it.

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Which 4K video should you buy?

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