Converting 25fps to 24fps?

Patrick Cooper · February 16

I shoot a fair amount of stock footage. And when I first started out, I chose to record at the frame rate that was native to my country - Australia (25fps.) A decision I would come to regret later. When I went over to the US for a short period of time, I was still shooting at 25fps unfortunately. Yea I'm kicking myself for doing that. I found out later that there are issues with artifacts when converting 25fps to 29.97fps. As such, a number of US clients may be reluctant to purchase my 25fps. And I particularly regret shooting at 25fps when I was in the US (filming urban scenes over there.) Obviously, converting 24fps to 25fps or alternatively 24fps to 29.97fps is fine.

Though how about converting 25fps to 24fps? Would there be any issues / artifacts in this scenario? I'm under the assumption that this would probably look okay (correct me if I'm wrong.) I could then use this approach and submit the clips to the stock agencies as 24fps (which is more universal than 25fps.) US clients could then convert that 24fps footage to 29.97fps with hopefully no issues.

With regards to what to do within the editing software, would it just be a simple case of selecting 24fps with the export options? Or would I need to slow down the footage on the timeline by a tiny percentage? If so, what percentage would you recommend? Would it be something like 1% or perhaps 0.5 percent? Ive no idea how to do this calculation.

Brian Drysdale · February 16

You may be able to select a 24 fps export on your NLE or change the frame rate of your sequence. The audio will also slow, which may be noticeable, You may not need a pitch change, but that depends on the nature of your soundtrack. There's a 4% speed difference, so the film will be longer.

24fps on NTSC frame rates has its own artifacts, but I guess they're so used to these, they're blind to them.

Patrick Cooper · February 16

29 minutes ago, Brian Drysdale said:

You may be able to select a 24 fps export on your NLE or change the frame rate of your sequence. The audio will also slow, which may be noticeable, You may not need a pitch change, but that depends on the nature of your soundtrack. There's a 4% speed difference, so the film will be longer.

24fps on NTSC frame rates has its own artifacts, but I guess they're so used to these, they're blind to them.

Luckily, I usually mute the audio on stock footage so that should be a non issue. Gosh, a 4% difference. I didn't realise it would be that much. I may be using Davinci Resolve for this. I admit I'm a new user to Resolve (Ive never used it before.) I believe with this software, there may be some settings you input when you start a project (including frame rate.) So perhaps I could type in 24fps here (as well as at the export stage.)

Oh yes a great point about US viewers likely not noticing the artifacts from converted 24fps footage. There's an interesting analogy that relates to sound rather than vision. Say someone who is not used to cicadas goes and stays in a place where there are lots of cicadas. And they ask: "What's all that noise?" And a person who grew up in cicada country would likely reply with: "What noise?"

Patrick Cooper · February 16

Edit: Maybe I should type 25fps into the project settings (after initially importing the footage) so that the NLE software recognises that it's 25fps to begin with. And then slow it down afterwards (by 4%) and type 24fps into the export settings.

I do have a small number of stock footage clips that I shot in the US but it took a number of years for any of them to sell. And only one of them has sold to date. This is despite the subjects not being covered by other stock footage online. I actually wonder if the lack of sales could be due to the fact that they were shot at 25fps. I have no issues with sales of stock footage featuring Australian content shot at 25fps. Though I do have many more of those Australian clips and a greater variety of subjects too. Surprisingly, I did have a 25fps city night scene shot in Australia that was purchased by a buyer in Los Angeles.

Regardless, I shoot most of my stock footage at 24fps these days.

Jon O'Brien · February 17

I think if you've shot at 25 fps and then start a new project in Davinci Resolve, and import the media to the timeline, a box will come up saying something like "the project has a different frame rate to the timeline. Do you want to change the framerate?" or something similar. You are also warned that the framerate can't be changed later. I've been shooting at 25fps too for all of my video work and I get asked this each time I start a new project on DR. It seems the default setting for the timeline is 24fps. So, each time, I click yes to change the framerate. When it comes time to export the project I notice that it's always set to the correct 25fps. Hope that's helpful.

I'm going to start shooting stock video footage too. Interesting. Sounds like there's more of a market for the 24fps footage.

Edited February 17 by Jon O'Brien

Brian Drysdale · February 17

I don't use Resolve, but there is online info on changing the frame rate.

I've got Lightworks, where you can make a conversion to 24 fps when making a copy of a 25fps sequence and when exporting the 24 fps copy, it's at that frame rate. However, it appears to still have the same running time, so may just have dropped frames.

Edited February 17 by Brian Drysdale

Patrick Cooper · February 17

Jon, with Davinci Resolve, I didn't realise that there's a warning that you can't change the frame rate later. So in my scenario with the 25fps footage, do you reckon it's best to accept the default setting of 24fps for the timeline? In that case, I'm not sure if I would still need to slow it down by 4%. Or perhaps I do as I vaguely recall one Resolve tutorial video that demonstrated slowing down the footage on the timeline that was shot at a high frame rate (if I recall correctly.) If we can't change the frame rate later (as per the warning) I guess the target frame rate has to be selected at the very beginning. But that's just a wild guess as I still haven't used this software.

Yea 24fps and 29.97fps seem to be the most universal frame rates so they're clearly the best choices when it comes to stock footage. It's a pity though that the stock footage industry is in a very bad way right now (especially for contributors.) The agencies are getting more and more greedy and trying to squeeze more money out of the content submitters. A lot of the commissions we get these days from sales are very pitiful. It was so much better just a few years ago. There still seems to be some people making decent money with large enough video portfolios (and of course good quality content.)

Patrick Cooper · February 17

Brian, that's what I assumed would happen if the track wasn't slowed down on the timeline but simply exported as 24ps - frames being discarded. In the case of 25fps being converted to 24fps, I guess one frame would be dropped for every second. I wonder if that would have any effect on the smoothness of the footage.

Mark Dunn · February 17

14 minutes ago, Patrick Cooper said:

I wonder if that would have any effect on the smoothness of the footage.

It would- this used to happen in reverse when some US material was shown on UK TV. A frame was repeated each second and it was quite noticeable.

Heikki Repo · February 17

My 16mm film camera has been set to run on 25 fps but I have sometimes accidentally (or intentionally) edited projects as 24 fps. I really can't tell any difference. Sometimes if I have had to change the fps to another, I have imported the rendered project to a different fps timeline and exported again. I haven't encountered any audio issues either. I work in Resolve. AFAIK it doesn't discard any frames, it just changes the playback speed.

Brian Drysdale · February 17

33 minutes ago, Patrick Cooper said:

Brian, that's what I assumed would happen if the track wasn't slowed down on the timeline but simply exported as 24ps - frames being discarded. In the case of 25fps being converted to 24fps, I guess one frame would be dropped for every second. I wonder if that would have any effect on the smoothness of the footage.

I suspect it's to avoid issues with the audio. There are a range of frame rates that you can convert to, and you wouldn't want the sound to change pitch at the higher frame rates.

Patrick Cooper · February 17

1 hour ago, Heikki Repo said:

My 16mm film camera has been set to run on 25 fps but I have sometimes accidentally (or intentionally) edited projects as 24 fps. I really can't tell any difference. Sometimes if I have had to change the fps to another, I have imported the rendered project to a different fps timeline and exported again. I haven't encountered any audio issues either. I work in Resolve. AFAIK it doesn't discard any frames, it just changes the playback speed.

That's good to know (with regards to Resolve.) It sounds like a nice simple conversion and efficient too. I gather there's no need to slow the footage down on the timeline and deal with percentages.

Heikki Repo · February 17

41 minutes ago, Patrick Cooper said:

I gather there's no need to slow the footage down on the timeline and deal with percentages.

That's correct, no need to do anything on the timeline, just have correct fps set in the timeline settings.

Patrick Cooper · February 17

1 hour ago, Heikki Repo said:

That's correct, no need to do anything on the timeline, just have correct fps set in the timeline settings.

That sounds great for projects where I want some slow motion footage. I have shot some 50fps footage in the past (specifically for slow motion.) It would be convenient to simply import it into a 24fps timeline and let the software do it's thing automatically with no discarded frames.

Heikki Repo · February 19

On 2/17/2024 at 5:09 PM, Patrick Cooper said:

That sounds great for projects where I want some slow motion footage. I have shot some 50fps footage in the past (specifically for slow motion.) It would be convenient to simply import it into a 24fps timeline and let the software do it's thing automatically with no discarded frames.

Just make sure that when you convert 25 -> 24 fps you have set in the Resolve General options the mixed frame rate mode to none. Otherwise it'll drop frames. This has to be selected before anything else is done, otherwise it's greyed out.

Patrick Cooper · March 3

On 2/20/2024 at 9:15 AM, Heikki Repo said:

Just make sure that when you convert 25 -> 24 fps you have set in the Resolve General options the mixed frame rate mode to none. Otherwise it'll drop frames. This has to be selected before anything else is done, otherwise it's greyed out.

Thank you for this important tip. Very handy to know.

Patrick Cooper · March 8

On 2/20/2024 at 9:15 AM, Heikki Repo said:

Just make sure that when you convert 25 -> 24 fps you have set in the Resolve General options the mixed frame rate mode to none. Otherwise it'll drop frames. This has to be selected before anything else is done, otherwise it's greyed out.

Out of curiosity, would this need to be done in other projects where you have shot the footage at 24fps and you want to export it as 24fps? Or 29.97fps footage that you want to export as 29.97fps?

Heikki Repo · March 8

This needs to be done only if you have different frame rate material on a timeline and you want Resolve to use it as raw frames instead of trying to maintain the same speed (ie. if you have 60 fps and 30 fps footage on 30 fps timeline and you want 60 fps play out as if it was shot 30 fps - because if this setting is set to none, the 60 fps footage is going to be slow motion among the 30 fps footage). No idea how it functions with fractional frames.

Patrick Cooper · March 9

Thanks for the clarification. It sounds like 24fps is the default frame rate for the timeline. I did read above that a message appears if someone wants say a 30fps timeline with 30fps footage. At least it sounds like that's the case.

Edited March 9 by Patrick Cooper

Heikki Repo · March 9

Yes, when inserting footage for the first time on the timeline it'll ask if you want to change the timeline frame rate - if it differs from the footage.