The number of video size formats available in even entry-level still cameras can be really challenging to understand. Here is what they are, where they came from and why.
Aspect ratios
These are the dimensions of a video screen shown as width to height. Standard television had an aspect ratio of 4:3. Modern HD TVs use a 16:9 ratio. Some cinema productions use different aspect ratios. When shown on an HD TV, black bars appear above and below the video to letterbox those ratios.
Still cameras typically capture in a 2 to 3 aspect ratio. For a landscape photo, this means 2 units tall and 3 units wide. Since video capture is typically in a 16 to 9 ratio the still sensor is cropped to the ratio at the time it’s shot.
Still cameras have a lot of pixels in the horizontal dimension. A prosumer Canon Rebel T8i’s sensor is 6000 pixels wide giving it plenty of resolution to capture several sizes of video even cropped to 16:9. The photos below are (L-R) 2:3 aspect ratio for full-frame and APS-C still DSLR and mirrorless cameras, 4:3 aspect ratio for standard broadcast television and 16:9 aspect ratio for HD video formats.
Of course, there’s a lot more to it. Before getting into the sizes — the resolutions of video, it’s important to understand the initials i and p.
1080i vs. 1080p
The way a video image is captured plays a large part in the quality seen on a screen.
(i) interlaced video
When an image is captured in an interlaced video, 1080i60, two fields make up one frame. This doubles the frame rate providing a smoother-looking video without using more storage space. Shooting video in 1080i means the camera captures a scene of 540 lines for the upper field — lines 1,3,5,7 … and then 540 lines for the lower field — lines 2,4,6,8 … On playback, the screen is refreshed 60 times a second but only with 540 lines at a time. The refresh rate is the last two numbers in 1080i60.
When the HDTV standard was set, processing power and the bandwidth for 1080p60 didn’t exist. Interlaced video is prone to artifacting but, thanks to its smaller size, it is the format for broadcast HD television.
(p) progressive video
1080p captures all 1080 lines for each frame of video. 1080p60 is twice the size of 1080i60. It does not show artifacting. Computer screens, phones and tablets are all progressive scans so shooting 1080p can be done at varying frame rates. Some videographers for television shoot 1080p30 (30 frames per second) and run it with a 1080i60 codec. Capturing video for television is beyond the scope of this article.
HD, Full-HD & UHD
These are the standards for television video today. All of them are in a 16:9 aspect ratio. That means that the long side is 16 units and the short side is 9 units. Typically this ratio is in the landscape position like the screen in a movie theater.
720p (HD)
This is the lowest resolution of high-definition video. It is 1280 x 720 pixels and each frame is about 9 tenths of a megabyte. These videos have relatively small file sizes.
1080i and 1080p (Full-HD)
1080i or 1080p is the standard right now. This video is 1920 x 1080 pixels. Each frame or in the case of interlaced video two frames contains 2,073,600 pixels.
1440p (Quad HD)
1440p is twice the size of 720p with a pixel dimension of 2560 x 1440 pixels. Each of these frames contains 3,683,400.
2160p (4K HD)
2160p is 3840 pixels by 2160 pixels. It is widely known as 4K or 4K HD. One frame has 8,294,400 pixels.
4320p (8K HD)
This is a great big format measuring 7680 pixels by 4320 pixels. A single frame has 33,117,600 pixels. It’s super large but that makes it a great format when a still camera has to zoom or pan a scene.
Why are there so many formats?
There is an answer for major motion picture cinematography and the one that works for still photographers.
Most work is going to be delivered in HD — 1920 x 1080 pixels. Wouldn’t it make sense to shoot only HD? That’s the obvious answer. Looking deeper, larger formats allow the still camera to make movie camera moves during editing. This video shows a smooth zoom in HD. It was shot in 8K. The scene starts with the whole 8K frame sized down to 25% to fit in the 1920 x 1080 HD format. The zoom is from 25% to 100%. Edited in Adobe Premiere Pro 2022.
Shoot large, edit small
Shooting everything in 4K gives a lot of room to move the 1920 x 1080 pixel frame within one that is 3840 x 2160. This is important because it is almost impossible to zoom a still camera lens and hold focus. The 4K format lets the editor make it smaller to fit into the 1920 x 1080 frame then zoom out. Or vice versa. This works to move through the frame side to side and up and down. To have a larger palette, shoot 8K.
Notes
Zoom lenses for still cameras are actually variable focal length lenses. A true zoom lens when set to its most telephoto focal length and focused will hold that focus through its entire zoom range. Variable focus lenses can’t do that. They have replaced true zooms because autofocus works so very well.
The larger the capture format the bigger the file sizes so there is a trade-off.
Video 101
Still photographers are using the video features in their cameras more and more. Like me, they probably wonder what all of the video jargon in their camera’s menus and manuals mean. Video 101 is written to help answer those questions.
