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Filmmaking Dictionary: Number 2 / 25 fps
Definition
25 fps means 25 frames per second. It is widely associated with television and production workflows in regions using a 50 Hz mains-frequency tradition. It is a whole-number rate, distinct from both 24.000 and 23.976 fps.
The frame rate does not specify resolution or scanning method. A 25-frame progressive image and an interlaced signal containing 50 fields per second require different handling even though both can be described using a 25-frame basis.
25p and 50i
In 25p, each frame is a complete progressive image. A conventional 50i signal contains 50 interlaced fields per second, with two fields making up each frame pair. Those fields may represent different moments in time. Treating them as interchangeable can create combing or lose motion information during conversion.
Read the full format specification and inspect the actual source. A filename or casual reference to ’25 frames’ may leave out whether the material is progressive, interlaced or carried using another transport arrangement.
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Shutter and Lighting
At 25 fps, a 180-degree shutter corresponds to 1/50 second. That is a useful starting point in many 50 Hz lighting environments, but it is not a universal guarantee against flicker. LED drivers, dimming methods, screens and other sources can behave independently of the nominal mains frequency.
Test the intended lights at the actual dimmer settings and shutter time. Review the recording, since a live monitor can make subtle banding or brightness variation harder to judge.
Converting 24 to 25
Playing every frame of a 24 fps recording at 25 fps makes the action approximately 4.17% faster. A 60-minute 24 fps programme becomes 57 minutes 36 seconds when simply played at 25. Audio timing and pitch need appropriate treatment.
A duration-preserving standards conversion is a different operation. It must handle the frame-rate mismatch while maintaining the intended runtime. Choose the method with the receiving broadcaster or post team instead of dropping the footage into another timeline and assuming the default result is acceptable.
Common Mistakes
- Confusing 25p with 50p or 50i.
- Assuming a 1/50-second shutter makes every LED fixture flicker-free.
- Changing playback rate without checking dialogue, music and programme duration.
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Frequently Asked Questions
Can 25 fps produce a film-like result?
Yes. The overall image and movement treatment matter more than treating 24 as a magic number.
Is 25 fps exactly 25?
In the normal format convention, yes. It is not the fractional equivalent of another rate.
Related Terms
Browse all terms starting with 2 or return to the filmmaking dictionary.