A film production released in regular theaters uses 24 fps (frames per second). This means 24 frames comprise one second of motion picture movement (1 minute or 60 seconds equals 1,440 frames). However, other figures are also typically used in a video production: the 23.976 (23.97) fps and the 29.976 (29.97) fps.
All these clearly exude such complicated and technical explanations, but this article intends to provide simpler explanations for the benefit of the curious, non-techie readers who want to have a basic understanding/insight of these terms that are often seen in editing and video technical specifications.
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The non-drop frame is used in the original timecode system because it assigns a progressive numbering to every frame. Here, progressive means numbers like 0 to 29 (for 30 frames). Although this is an accurate way of tracking individual frames, this causes a problem for editors when comparing the elapsed “real time” to the “videotape real time” employed in the post-production process. This is because the video actually runs at 29.97 fps and not exactly 30 fps. This results to a video that goes off sync by 3.6 seconds at the end of a one-hour video. Take note that even a one-second discrepancy on the audio and video readily shows the problem (watching the video with off-sync sound).
To synchronize the actual time as how clocks measure it and the elapsed time counters used in a video editing system, video engineers developed the drop-frame timecode to technically work like a leap year in reverse. For a drop frame timecode, two frames are dropped or skipped every minute, except when the number of the minute ends in a zero, such as the minutes: 00, 10, 20, 30, and so on.
Frame Rate Converters
Post-production houses are ideally equipped with frame rate converters to convert from one timecode system to another.
29.97 fps is the standard timecode frame rate used for video. This means that the video footage is recorded at 29.97 fps, along with the audio recorder also utilizing the same timecode speed of 29.97 to match the master video recorder. However, if recording for a film shoot (for big screen projection and not on TV), the process and general settings used are different. In such case, the footage to be shot should generally be in 24 fps.
Unlike in theatrical projection in a movie house, its version shown on TV is in 23.97. Any 24 fps video is not really 24 when shown on a TV set. It is actually 23.97 fps. However, a video shot with the intent of converting to film can actually be 24 fps. The workflow done during post-production requires more specific parameters which affects the decision on the frame rate to use during the shoot.
For a film shot in 30fps, the footage would end up 29.97 film speed in the video domain. For film cameras (non-digital or non-HD cameras), other frame rate options can be 24 fps, 25 fps, and 30 fps.
Using Drop or Non-Drop Frame
When recording for a video shoot, it is alright to use drop or non-drop frame, as long as it’s the one used by the videotape recorder. Productions intended for TV broadcast usually prefer the drop-frame mode. The production’s video engineer, camera operator, and/or technical director is/are typically responsible for the decision. However, for film-style editors, they usually prefer using the non-drop timecode to keep track of all frames of the footage. This eliminates confusion during post-production work, especially when dealing with complicated special effects or when converting from video (TV) to film (big screen). Unless otherwise instructed due to more project-specific reasons, the non-drop timecode system is used for film productions.
The normal frame rate used in recording audio to be synced to film cameras is 30 fps, whether the film camera is officially running at 24 fps or 30 fps. This may sound quite confusing, but the reason for this is that the audio does not have to correspond with visual frames completing a one-second footage, and so on. Moreover, the sound doesn’t have to literally match the film speed in almost all cases now. The sound would rather match the video speed since the editing these days is practically done using the non-linear system, meaning editing through a digital video platform.
For an originally captured footage in 24 fps transferred to video for editing purposes, everything is slowed down by one tenth of one percent.
The slowed down process ends up with the equivalent film speed in a video environment: 23.97. This involves the process known as a 3:2 pull-down, meaning, 12 half-frames or video fields are added to the 23.97 frames accordingly. This results to an extra one field produced every other picture frame scanned or digitized. This creates additional 12 fields without altering the running speed of the picture because it is only “slicing the same bread into smaller pieces.”
Syncing Audio and Video
When shooting with a film camera, since the video is slowed down in the video platform, the audio must remain in sync by getting slowed down by the same percentage as the video. Once editing is completed and the film is ready for blowing up to film prints, the audio must be returned back to 24 or 30. In general, unless otherwise instructed, the industry standard for production sound used for film shoot requires setting the timecode in the audio recorder to 30 fps non-drop.
“When Durations Don’t Match in Viewer and Canvas,” Larry Jordan.
“How to Use Drop Frame or Non-Drop Frame,” B&H.
“Drop Frame vs. Non-Drop Frame Rate,” GeniusDV.
“Final Cut Pro Documentation: About Drop Frame and Non-Drop Frame Timecode,” Apple.
Other Related Production Articles:
How to Make a Show Reel
Old School Film Editing Machines: Moviola and Steenbeck
How to Edit Movies and Burn Them to DVDs
How to Burn HD Footage to DVD
How to Convert VHS Tapes to DVD Discs
How to Transfer Film to Video