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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

23.98 VS 24

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Steve Roberts

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Can someone shed some light on the exact differences between 23.98 and 24 fps project bases?
If I shoot a project in 24 and never end up doing a film out, how will impact it going to Blue Ray vs 23.98?
 
IIRC, 23.98 is strictly an HD video format (IE- Canon is lying to you when they say 1080p24 on their DSLRs; the acquisition is actually at 23.98fps). I don't know the science behind this, but it's probably something stupid like why NTSC-DF exists.

Since they are both progressive formats, you won't have any issues if you decide to conform your project at 24fps going to Blu-ray vs 23.98.
 
Steve Roberts said:
Can someone shed some light on the exact differences between 23.98 and 24 fps project bases?
If I shoot a project in 24 and never end up doing a film out, how will impact it going to Blue Ray vs 23.98?
Click to expand...

Im probably going to shoot myself in the foot here but...

My guess would be that 24fps is an ANALOG-FILM project time base. And that 23.976 is an HD project time base that takes into account "DROP FRAME".

I work in broadcast and we only work in drop-frame 23.98/29.97/59.94 projects.

Someone will probably step in and tell me I'm wrong, but that's my guess. I would say shoot 23.98 to be safe, as the world is going digital.
 
Doug Beatty said:
IIRC, 23.98 is strictly an HD video format (IE- Canon is lying to you when they say 1080p24 on their DSLRs; the acquisition is actually at 23.98fps). I don't know the science behind this, but it's probably something stupid like why NTSC-DF exists.
Click to expand...

This goes back to the first NTSC standards way back in the 1940s. The first standard was black and white with a single luma channel, 30.00 frames per second (interlaced 2 x 60 fields per second). When the time for colour came around, in the 50s I think, NTSC decided to add chroma channels to the already existing luma channel. However, FM sound interfered with the frequency of chroma channels, leading to interference patterns on the images. To fix this, the frame rate was hastily slightly offset by a factor of 1.001. This led to 30 fps becoming 30/1.001 or approx 29.97 frames per second (once again, 2 interlaced fields at 29.97x2 fields per second). FCC had originally rejected the NTSC system and chosen a competing standard (I forget the name) which had 24.00 fps from 144 interlaced fields. For some reason FCC changed their minds and went for the NTSC 29.97 standard instead. Anyway, later, the need for an alternate standard with frame rate closer to 24 fps of cinema meant that the 30/1.001 was pulled down by a factor 1.25 to arrive at 23.976 fps. These quirks have stood the test of time and somehow carried over to the digital era. Here we are today, shooting at 23.97602398 fps.

As Mark mentions above, the PAL standard makes much more sense. 25.00, 50.00 or nothing.
 
Sometimes you need to shoot 23.97 when you need video transmitter or another HD device that don t synchronise with true 24 progressive signal.

Pat
 
For a long time, one reason for shooting at 23.976 fps was because that post was done using NTSC video transfers, so even if you shot film at 24 fps, it was transferred at 23.976 fps to video for distribution to editors at 59.94i. And generally sound editors would receive videotape copies of the offline cut and edit to that. In the end, the whole thing had to be resolved back to straight 24 fps for feature films.

And once 60 Hz countries chose to continue 59.94i for 1080 HDTV broadcast, the problem really hasn't gone away.

I did one of the first 24P HD movies on the F900, "Jackpot", in 2000 and the Sony F900 had the option of 24P or 23.98P... I chose 24P. Later I asked how the sound mix was going and the editor told me that they had to shift whole reels over slightly to get them to stop drifting in sync, so I suspect that was partly due to shooting in 24P instead of 23.98P but editing in NTSC. Of course editors can now work in true 24P and they can send that to sound editors who can work at true 24P on their systems, but for some reason, the whole chain still works using dubs in 59.94i.
 
Thank you, David. It is nice to get a definitive answer with a little history lesson thrown in.
 
that's odd because i was taught the reason for this nightmare was the first black and white tv's only understood a black and white signal and when color came out the b&w tv's didn't understand what they were receiving so in order to keep piece they took part of a frame to send a signal to tell or trick the tv into thinking it was a b&w signal. at least this is what they taught in school.... and read many times/ go figure. i guess this is why they are still doing script rewrites on the 65th day of shooting.....................
 
Steve Roberts said:
Can someone shed some light on the exact differences between 23.98 and 24 fps project bases?
If I shoot a project in 24 and never end up doing a film out, how will impact it going to Blue Ray vs 23.98?
Click to expand...
The difference is .1%. :biggrinjester:

I generally tell my post clients to shoot it all in 23.98fps, then at the very end of the workflow, do a .1% pull-up (which has no effect on picture or sound quality) and deliver for DCP at 24.00fps. 23.98 is much easier for everybody to deal with, as a general rule.

If there's any doubt, talk to your editor and/or post supervisor and have them check with their post vendors (picture and sound) and find out what is preferred. There's always the possibility that it's a project for overseas delivery where 25fps is actually a better idea. But in most cases, I think 23.98 is the right way to go, even for theatrical.

Note that the feature will run about 3 seconds faster per hour at 24fps vs. 23.98, so you're looking at roughly a 6-second difference for a 2-hour film. Not a big deal, but it is something that the sound people need to be aware of so they can compensate if necessary during the layback.
 
Marc Wielage said:
The difference is .1%. :biggrinjester:

I generally tell my post clients to shoot it all in 23.98fps, then at the very end of the workflow, do a .1% pull-up (which has no effect on picture or sound quality) and deliver for DCP at 24.00fps. 23.98 is much easier for everybody to deal with, as a general rule.

If there's any doubt, talk to your editor and/or post supervisor and have them check with their post vendors (picture and sound) and find out what is preferred. There's always the possibility that it's a project for overseas delivery where 25fps is actually a better idea. But in most cases, I think 23.98 is the right way to go, even for theatrical.

Note that the feature will run about 3 seconds faster per hour at 24fps vs. 23.98, so you're looking at roughly a 6-second difference for a 2-hour film. Not a big deal, but it is something that the sound people need to be aware of so they can compensate if necessary during the layback.
Click to expand...

Marc, your post brings up a question a little off topic. What if a production plans on an NTSC release AND a PAL release? How do you accommodate for that with sound? By that I mean, do you record sound as you normally would for an NTSC release (assuming that is your native tongue '-) and rework the math in post?
 
Elsie N said:
Marc, your post brings up a question a little off topic. What if a production plans on an NTSC release AND a PAL release? How do you accommodate for that with sound? By that I mean, do you record sound as you normally would for an NTSC release (assuming that is your native tongue '-) and rework the math in post?
Click to expand...


PAL releases of US and Canadian made television programs have been made for years. The general approach today is to make a 23.98 master and create everything from that. For 60i, a 2:3 fielded pulldown pattern is added. For 50i, the material is played 4% faster and fields are created. Most of the world is used to hearing voices that are a bit "higher" than the actual actors' voices because they have been hearing them that way for a long, long time. There are some shows that do pitch correction, but in my experience, not very many. 25 frame HD is a bit of a different story in some cases because there is enough information there to use a "standards conversion" approach, basically an interpolation from 24 to 25 without altering the actual running speed. So that is an alternative assuming there is an HD master, which there always is today.
 
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