(Page 1 of 9 pages for this article 1 2 3 > Last »)
Monday, November 03, 2008
When 25p beats 24p…
Allan Tépper | 11/03- 03:50 PM
How to pick the best workflow… and the best version of a “segregated” camcorder to avoid being Twisted into knots
There are many times when it makes more sense to shoot and edit video at 25p than at 24p, regardless of the final framerate(s) to be delivered to various distribution formats, even if you live in an NTSC (or ex-NTSC) country. You may know that “24p” video is almost always really recorded at 23.976p (although Apple and some camera manufacturers often like to round it to “23.98p”). This article is about:
- Why and when you would want to shoot low framerate video at all.
- In many of those cases, why it often makes more sense to shoot and edit at 25p instead of 23.976p.
- The reasons why with certain “segregated” camcorders, you are much better off purchasing or renting the 25p/50Hz version, even if you live in an NTSC or ex-NTSC country.
- 25p workflows: How to go from your 25p universal master to all imaginable output formats.
Why and when to shoot low framerate video at all
When I say low framerate, I’m referring to anything 25p or lower. When I say medium framerate, I mean 30p (29.97p). When I say high framerate, I’m referring to 50p or 60p (59.94p). (I am a progressive guy, but I will mention interlaced later on!)
If you live in the (up until now) NTSC world, the main reasons why you might want to shoot low framerate video for your “normal” footage (as opposed to your slow-motion footage) are:
- To achieve one of the many aspects of the “film on video” look (This is equally feasible whether you shoot at 23.976p or at 25p, since the look is the same).
- To have an easier path to filmout (This is equally feasible whether you shoot at 23.976p or at 25p, since both will require a slight audio pitch adjustment when exporting for filmout at true 24.000p with a 1:1 frame relationship--more details later).
- To be able to deliver on NTSC “24p” DVDs or “24p” Blu-ray disks, both of which are really 23.976p (Both are equally feasible whether you shoot at 23.976p or at 25p using a similar audio pitch adjustment upon export).
- To be able to deliver full-raster 720p-HD to the current AppleTV device. [Despite the imprecise information posted at Apple’s USA, UK, Spain, Latin America, and Australian websites, the current AppleTV will actually accept full raster 1280x720 at a maximum framerate of 25p. Those four Apple websites imprecisely indicate that the maximum supported HD signal is 1280x720 @24p. (Apple is underrating the product.) I have personally verified with several AppleTV units in the USA, and they have always worked fine with full raster 1280x720 @25p footage, even when matched with a 60Hz-only monitor or projector via HDMI. With anything higher than 25p, the current AppleTV needs you to downscale the spatial resolution of your HD footage to 960x540 to keep up with the higher framerate. If you have clicked the above links and it now says 1280x720@25p (or 25fps), it means that Apple has now corrected their websites
 ]
(Page 1 of 9 pages for this article 1 2 3 > Last »)
Hello Allan, very interesting and researched article. However it has a few glaring inaccuracies which could be misleading.
1-Cinema Tools or the FCP “Tool>Conform 25 > 24” does NOT conform a 25p clip to 23,976. It conforms it to 24p. Cinema Tools was created to facilitate the transfer of 35mm material in and out of NLE. As such, it enables someone to prepare a clip for a 24fps 35mm telecine. 24p and 23.976 are 2 separate things (which is why HDCAM CineAltas can usually be switched between 24p and 23.98 depending on wether you are shooting a theatrical film or TV broadcast/DVD etc). 24p is used as a 1:1 film workflow framerate. 23.98 is necessary for NTSC broadcast because 24 is not “pullable” mathematically to NTSC 29.97 (A telecine runs at 24/1.001 fps (23.98) so that it can transfer easily to NTSC).
If you convert a clip in Cinema Tool/FCP and open it with QuickTime, you will even see that it’s frame rate is properly shown as 24. If you then convert it to NTSC DVD 23.98 in Compressor and open that .m2v clip in QuickTime you will the frame rate again correctly shown as 23.98.
2- FCP does NOT automatically adjust the audio pitch of a clip after performing a 25>24 conform. After reading your article, I thought the software had been updated without my knowledge and I just tested it again with a 25p/1080p 90 min file in Prores422. The audio is obviously not pitch-adjusted. The female cast members sound like my uncle Joe and the music is atrociously out of key. a AUPitch adjustment is necessary. I have performed this many times and it works flawlessly.
3- It is erroneous to say that film in theaters are projected at 48p and that consists of some sort of alteration (or correction as you put it) over the 24p material. First of all there is no “p” in film. Film is projected at 24fps. You film is shown 1 frame at a time, 24x a second but for 1/48th of a second because the projector’s shutter has to close up while the film is advanced to the next frame. This is not to reduce flicker as you mention but in fact to create it! This stop and go “stroboscopic” effect is what allows film to exist. Persistence of vision allows the last frame of the film to stay in your eye while the film is advanced to the next. Your eye therefore perceives it as a smooth film playback. Otherwise, you would just see a colored blurring racing down the screen!
This is a mechanical device that is necessary for the visualization of a film strip, but your film is shown again at 24fps, 24 frames per second just as your 24p video clip would be shown at 24 frames per second in a video player that does not require persistence of vision for your eye to properly register the information.
Regards
JF Leduc
Posted by on 11/07 at 09:16 AM
JF, I’m very interested in your (2) comment here. I am currently working on a PAL based project - a feature length film sourced on PAL DV. When I read Allan’s article I thought I would be able to get around the pitch correction issue. But as you noted this doesn’t work. My question for you is. What settings are you using with AUPitch. I get phase shifting throughout. There are many paramerters in AUPitch. I just need to adjust the audio back up to the original pitch. So I’ve taken to doing a time stretch in Soundtrack Pro. This works better but not perfect. And it requires quite a few steps. Any recommendations would be most helpful, thanks. pw
Posted by on 11/12 at 06:35 AM
Excellent article. I did use similar methods in some films.
One thing which is really important to mention is artificial light. You may run into trouble with that as there is still 50/60 Hz.
Andreas
Posted by on 12/21 at 10:20 AM
|
