The same content today often has to be published in different shapes: landscape for the website and traditional players, vertical for stories and short videos, square or 4:5 for some feeds. If aspect ratios are handled badly you get pointless black bars, cropped faces, text off screen or distorted pictures. Understanding how aspect ratio works and planning from the shoot onwards lets you produce every version without surprises.
Aspect ratio and resolution
Aspect ratio is the ratio between the width and height of the picture. The most common ones:
| Ratio | Example resolution | Typical use |
|---|---|---|
| 16:9 | 1920×1080 | television, web, traditional players |
| 9:16 | 1080×1920 | vertical smartphone videos |
| 1:1 | 1080×1080 | square feeds |
| 4:5 | 1080×1350 | vertical feeds taking less space |
| about 2.39:1 | 1920×804 | widescreen cinematic look |
| 4:3 | 1440×1080 or 640×480 | old television, archives |
Resolution is the number of pixels; aspect ratio is their overall shape. Two videos can have different resolutions and the same ratio, such as 1280×720 and 3840×2160, both 16:9.
Square and non-square pixels
In modern video, pixels are almost always square: the shape of the picture matches the ratio between horizontal and vertical pixel counts. In older formats this was not the case. A European DV video at 720×576 may be displayed as 4:3 or 16:9 depending on the pixel aspect ratio declared in the file. If this information is lost, people look squashed or stretched.
Containers store two useful values:
- SAR (sample aspect ratio): the shape of a single pixel;
- DAR (display aspect ratio): the ratio at which the picture should be shown.
When converting old material, it is best to turn it into square pixels with an explicit scale, so no player misreads it.
Three ways to fit a video to another ratio
1. Black bars (letterbox and pillarbox)
The whole picture is placed inside the new format and the remaining space filled with bars: top and bottom (letterbox) or at the sides (pillarbox). Nothing of the framing is lost, but on a vertical screen a landscape video becomes a small strip in the middle.
2. Cropping
A portion of the picture is cut out at the new ratio. The video fills the screen, but part of the framing is lost. From a 1080p 16:9 frame you can obtain a 9:16 by cropping a central strip about a third of the picture's width, with an obvious loss of resolution if it is then enlarged.
3. Dynamic reframing
The crop follows the subject, moving over time: for example, it frames whoever is speaking when the speaker changes. Many editing programs offer automatic reframing tools, which should always be checked by hand.
The blurred background
A variant of black bars fills the empty space with an enlarged, blurred copy of the same video. It is more pleasing than bars, but does not solve the problem of the small picture.
Planning at the shoot
The best solution is decided before shooting:
- shoot at a higher resolution than the final one, for example 4K for a 1080p delivery, so you can crop without losing too much definition;
- leave room around the subject, so that a vertical crop does not cut off the head or hands;
- keep the subject near the centre if you know a vertical version will also be needed;
- use the framing guides many cameras offer to show the area of a 9:16 inside a 16:9.
Text and graphics
Captions must be designed for each format. A title placed near the edge in a landscape video may disappear in the vertical crop. In addition, app interfaces often cover the bottom and sides of the screen with buttons and captions: keep important text in a central safe area.
Exporting with FFmpeg
Centre crop from 1920×1080 to 9:16, scaled to 1080×1920:
ffmpeg -i landscape.mp4 -vf "crop=ih*9/16:ih,scale=1080:1920" -c:v libx264 -crf 20 -c:a copy vertical.mp4
Placing a vertical video in 16:9 with side bars:
ffmpeg -i vertical.mp4 -vf "scale=-2:1080,pad=1920:1080:(ow-iw)/2:0" -c:v libx264 -crf 20 -c:a copy pillarbox.mp4
The setsar=1 filter after scaling ensures the pixels are declared as square.
A tidy workflow
- Edit the main version in the format it was conceived for.
- Duplicate the sequence for each additional format, setting the new ratio.
- Reposition the framing and move text clip by clip.
- Export each version with a name indicating its ratio, for example
promo_9x16.mp4.
In short
- Aspect ratio is the picture's shape, resolution the number of pixels.
- With old material, check the pixel aspect ratio to avoid distortion.
- To change format you use bars, cropping or dynamic reframing.
- Shooting at higher resolution and with room to spare makes several versions possible.
- Keep text inside a central safe area.
