4.2.3
Moving image files
Moving images are just a lot of still frames in a row. Frame rate is how often they change, resolution is how much detail is in each one, and compression decides whether anyone can actually stream it.
On this page7 sectionsHide
What you need to know
- Explain frame rate and video resolution without mixing them up.
- Recognise SD, HD, UHD, 4K and 8K.
- Compare video and animation formats and their limitations.
- Justify a quality and file-size choice for a named use.
Start here
Frame rate: how often the picture changes
Frame rate is how many frames are shown each second, in fps. At 30 fps you see 30 frames in a second. Capture and display at a higher rate and fast movement looks smoother, which is why it matters for sport or a quick demonstration.
More frames per second also means more frames to process and store for the same duration. What it does not do is make any individual frame sharper — a blurry source, bad lighting or heavy compression will still look exactly as bad at 60 fps. And repeating frames from a low-fps source does not add moments of movement that were never captured.
Learn the list
Resolution: how much is in each frame
Video resolution is the pixel width and height of the picture. More pixels can show finer detail, when the source has it and the screen can display it. It also pushes up processing, storage and bandwidth. A clip destined for phones does not need what an exhibition display needs.
SD is standard definition, HD is high definition, UHD is ultra high definition. These are families rather than single sizes, so learn the order and the common examples — and do not confuse the number of pixels with the number of frames per second.
| Label | Common example | What it means for the choice |
|---|---|---|
| SD | 720 × 576 in a common UK standard | Less detail than HD, and limited if enlarged. |
| HD / Full HD | 1280 × 720 / 1920 × 1080 | More detail, and the usual size for screen and online delivery. |
| 4K UHD | 3840 × 2160 | More detail for displays that can show it — bigger files, heavier playback. |
| 8K UHD | 7680 × 4320 | A very high pixel count, only worth it when source, display and workflow all justify it. |
Use the numbers you were given
Cinema 4K uses a different width from consumer 4K UHD. If the scenario states dimensions, work from those rather than assuming the label overrides them.
Learn the list
Video and animation formats
Animation builds movement from designed frames — drawings, models, objects. Video records a moving scene. But animation gets exported as a video file all the time, so a video extension does not prove a camera was involved.
Uncompressed moving-image data is enormous. Lossless compression preserves the encoded information; lossy discards some to get it smaller. Push lossy compression hard and you see it: blocks, smeared movement, lost fine detail. A delivery export usually uses compression even when the production master keeps more.
| Format | What it gives you | What to watch |
|---|---|---|
| MP4 | The common delivery container for compressed video and audio, supported almost everywhere. | Quality and compatibility come from the codec and export settings, not the .mp4 on the end. |
| MOV or AVI | Used in video workflows, and can carry video compressed in different ways. | Can be large or need particular playback support. Neither extension guarantees uncompressed video. |
| Animated GIF | A short looping animation, displayed almost anywhere online. | No audio at all, and a limited colour palette per frame. Wrong choice for a detailed film with narration. |
In the exam
A sports-centre promotional clip
Animated GIF would be the wrong call for this clip regardless of the destination: no audio means no narration, and a limited colour palette handles photographic footage badly.
Worked answer
4 marks
A sports centre wants a promotional clip of fast exercise movements, shown on its website and on a large display in reception. Justify your frame rate, resolution and format choices.
Tempting, but this does not score
Export it in 8K at the highest frame rate so it looks as good as possible on both the website and the big display in reception.
The highest setting is not the right answer when one of the two destinations is a website. An 8K file punishes every visitor on a limited connection, for detail their screen cannot show anyway.
Worth writing
Shoot at a higher frame rate, because the exercise movements are fast and a higher rate makes that motion look smoother. For the website, export a well-encoded HD version as MP4 — visitors on limited connections get a clip that actually plays, and HD carries enough detail at the size it is watched. For the reception display, check its native resolution and what its player supports, then export to match and test the file on that actual screen before it goes live.
Where the marks come from
- Ties frame rate to the specific content — fast movement.
- Justifies HD for the website by what the audience’s connection can handle.
- Treats the two destinations as separate exports rather than one compromise.
- Ends with testing on the intended equipment, which is what catches playback problems.
Key takeaways
- Frame rate counts frames per second. Resolution counts pixels in each frame.
- Higher of either means more data for the same length of video.
- A higher frame rate does not make any individual frame sharper.
- Animated GIF has no audio and limited colours per frame.
- The .mp4 extension is not a quality rating — the encoding settings are.
Glossary
- Frame
- One still picture in a moving-image sequence.
- Frame rate
- How many frames are captured or displayed each second, in fps.
- Resolution
- The pixel width and height of a frame.
- Codec
- The method used to encode and decode the video or audio inside a container.
- Container
- A file structure holding video, audio and related information — MP4, for example.
- Bandwidth
- How much data a connection can transfer over time.
Test yourself
5 questions
What does 60 fps measure?
A frame rate of 60 frames per second — not pixels.
What is the difference between frame rate and resolution?
Frame rate is how often the frames change. Resolution is the pixel width and height of each one.
Why is animated GIF wrong for a promotional film with narration?
GIF carries no audio, so the narration is lost, and its limited per-frame colour handles photographic footage poorly.
Why might HD suit mobile distribution better than 8K?
It needs far less data, so it loads and plays reliably on the target devices, and still has enough detail at the size people watch it.
Does a higher frame rate make each frame sharper?
No. It makes movement look smoother. Sharpness comes from the source, the lighting and the resolution.
Common questions
Is every MP4 the same quality?
No. Source, resolution, frame rate and compression settings all decide that. MP4 is a container, not a quality level.
Can an animation be delivered as a video file?
Yes — exported as MP4 or another supported format, with sound if the format carries it.