Video jargon can quickly get complicated, and can seem even worse to stills photographers who’ve learned a whole lexicon of photography concepts and terms and now have to do the same with the very different world of video.
But the video basics are comparatively simple and easily learned, and the rest can follow from that. The key concepts are resolution, aspect ratio and frame rate.
Video resolution works in much the same way as camera resolution. It’s simply the dimensions of the video frames in pixels. There are a couple of differences, though.
In stills photography we talk about megapixels rather than width or height in pixels, and there are no ‘set’ resolutions – you can get cameras with 12, 20, 24, 26, 32, 42 megapixels and so on. In video there ARE set resolutions, and these are defined both with names and numbers.
When HD video first appeared (remember that?), it came in two resolutions. Standard HD has a resolution of 1,280 x 720 pixels. These days this is usually shortened to just the vertical resolution and quoted as ‘720p’ (we’ll come to the ‘p’ part shortly). Full HD has a higher resolution of 1920 x 1080p and is usually shortened to ‘1080p’. This is the minimum resolution for most cameras today.
And then came the 4K video revolution. Here, the video industry swapped to measuring the width of the frame in pixels, not the height. So ‘4K’ video is video with a horizontal resolution of around 4,000 pixels. It’s not exact because there are a couple of different formats, but it’s close enough in most cases for the distinction to be just a technical one.
4K is not the end. You can already get 6K video cameras with a horizontal video resolution of around 6,000 pixels. The Panasonic Lumix S1H is one example, the Blackmagic Pocket Cinema Camera 6K is another. Sharp, Panasonic and other camera makers are also working on 8K video cameras with a horizontal resolution of around 8,000 pixels.
This is a good time to talk about aspect ratios. This is the ratio of an image’s width to its height, and it’s especially important in video where you want to make sure your video’s aspect ratio matches the aspect ratio of most users’ monitors and TV screens.
Here, the 16:9 ratio has become a near-universal standard, though other aspect ratios are used in some instances. Cinematographers and professional filmmakers will user wider aspect ratios still for theatrical releases, but that’s at a much higher level than most of us will operate.
At a consumer level, the aspect ratio of popular video formats is almost universally 16:9. From standard HD through full HD and 4K, the aspect ratio is the same, even though the resolution varies considerably.
Though 4K shooting does bring a complication. When most people talk about 4K they’re referring to ‘4K UHD’, to give it its correct technical term. 4K UHD has a resolution of 3,840 x 2,160 pixels. So it’s not QUITE 4K as far as the horizontal resolution is concerned, but for most users it’s close enough and it does have that standard 16:9 aspect ratio.
Some more advanced cameras also offer a ‘Cinema 4K’ option (also called DCI 4K or C4K). This has the same 2,160 pixel vertical resolution but is slightly wider with a horizontal resolution of 4,096 pixels. You might say it’s ‘genuine’ 4K, but it has a slightly wider and more awkward 1.90:1 aspect ration.
It’s likely we’re going to see more variation in video aspect ratios in the future as videographers and filmmakers target the screens on mobile devices not just TVs and computer monitors.
Video frame rates
Video frame rate is, as you might expect, the number of frames of video captured per second. In stills photography you might say ’10fps’ or ‘20fps’, for example, but in video it’s usual to quite the number followed by the type of capture – ‘interlaced’ (i) or progressive (p).
Interlaced video is an old technology you hardly ever see now. It comes from the days when processing power and transmission speeds were low. Each ‘frame’ consisted of either the odd or even ‘rows’ in the video capture, and these odd/even frames were then alternated or ’interlaced’ during playback and transmission and most of the time you wouldn’t notice the difference. Where a camera uses interlacing, the frame rate is followed by an ‘i’, so a frame rate of 30i is 30 frames a second but shot ‘interlaced’.
Almost all cameras now shoot progressive video, where each frame is captured in its entirety. This is shortened to ‘p’, so that if a camera’s specs quote a frame rate of 30p, that’s 30 ‘progressive’ (full) frames per second.
Adding ‘p’ to the camera’s frame rate (or its resolution) has become standard practice, even though interlaced video has pretty much died out. (Sometimes you’ll see cameras with 1080p resolution – this means they can shoot progressive (not interlaced) full HD video.
Video frame rates are sometimes based on the region where the video is to be played back. Some territories, include North America, use the NTSC standard, while others, including Europe, use PAL. These are old standards with limited relevance today, except for frame rates. NTSC is based around a frame rate of 30fps, while PAL is 25fps. Changing frame rates for captured video is not ideal so some filmmakers might choose a frame rate that suits the territory where their work will be distributed.
Most cameras offer a choice of 30p and 25p frame rates, and some also offer 24p – 24fps is popular frame rate for cinematography and gives footage a characteristic film ‘look’ according to fans.
Slow motion and timelapse video
Most video is shot and played back at the same speed, e.g. 30fps. However, you can create a different effect by capturing video with a different frame rate.
For example, if you capture video at 60fps and then play it back at 30fps, you get a 2x slow motion effect. Some cameras can capture video at 120fps (albeit at a lower resolution) for a 4x slow motion effect.
Alternatively, if you capture video frames at far wider intervals and then play them back at 30fps, you will get a speeded up ‘timelapse’ effect. Usually, timelapse sequences are captured as a series of stills at fixed time intervals a second or more apart, and then combined as sequential video frames either in-camera or using video editing software later.