Sigh, there is no frame rate in an image sequence. You have to set it. Some software may add some meta-data that suggests a frame rate but in AE you have to choose. You have changed nothing by interpreting the footage at 24 frames per second and then rendering a new image sequence. All you have done is re-render the frames and waste a bunch of time. You will still end up with 141,000 frames.
In your AE Preferences there is a place to set the interpretation for image sequences. Yours is set to 25 frames per second. I have mine set at 29.97 frames per second. If I was working on a project that was 24 frames per second I would change the preferences.
The only time you would need to re-render an image sequence is if the original image sequence was synchronized to an audio track and the running time is critical. If the original image sequence was 24 frames per second and you had to produce something to be played back at 29.97 frames per second you would change the interpretation to 23.976, and if the video was longer than about 10 minutes you would Timestretch the audio, then you would render 29.97 frames per second interlaced and add 3:2 pulldown for the smoothest playback. That's how they have put movies on US television sense color television changed the frame rate from 30 to 29.97.
Since you are sending an original 25 frames per second image sequence to to make a DCP all you have to do is tell them you want the DCP at 24 frames per second. If there is audio involved and sync sound and the running time is absolutely critical then you interpret the original image sequence at the original frame rate of 25 and put it into a composition set to 24 and you accept the fact that you are going to have some blended frames. For 91 minutes I would do that in Premiere Pro instead of aftereffects anyway. It will save you hours of rendering, but you probably don't need to do any of it. The folks making the DCP will have better tools than you do to maintain sync, running time, and drop or blend the occasional frame.
In most cases with long projects if the original is 25 frames per second and the target is 24 you just live with the time difference and slow down the sound to keep things in sync. The folks that make movies and show movies in the US and Europe have been doing this for about 100 years. What I am trying to say with this long-winded explanation is that you don't have to do anything at all to your footage except send your image sequence out and tell the folks doing the conversion that the original was 25 frames per second and the target is 24. If anything needs to be adjusted they will do it. The only difference that you will notice is that the 94 minute movie now takes just a shade under 98 minutes to watch.
No, of course I have to do something. I will convert the 25p 16bit tiff sequence to 24p, in Aftere effects (since only After effects can render 16bit tiff images), then I will fix the sound channels and then I will make the master DCP (not with free DCP builders). I have purchased a very good professional DCP builder software. I will do everything myself. So I will fix this thing with tiff framerates in After effects and procceed...
You missed the point. Image Sequences do not have a free rate. You have to tell an image sequence what frame rate you want to use. The behavior is not odd, you do not understand how frame rates and image sequences work.
If you interpret footage as 24 fps and put it in a 24 fps comp then you still have every single frame. If your original footage was 1000 frames long and you interpreted the footage as 10 fps and put it in a comp that was 10 fps you would still have 1000 frames and when you rendered the footage you would still have the same 1000 frames. If your 1000 frames was interpreted as 24 fps and you put the footage in a comp that was 24 fps and you rendered the footage the you would still have 1000 frames. The only difference between the two comps is that the 10 fps comp would be 100 seconds long and the the 24 second comp would be 41 seconds long. You would still have the same 1000 frames. If you are not applying any effects to the image you have changed nothing about the image sequence. Your workflow does not change the number of frames.
Let me go over that one more time. The original footage, according to your first post you have a 16 bit image sequence that is 94 minutes long when the frame rate is set to 25 fps. I'm now assuming that you also have an audio track that is 94 minutes long. The audio track does not have a frame rate, it has a sample rate and a fixed length. The sample rate of the audio track does not change. The running time of an audio clip does not change if you change the frame rate of a comp. If you change the frame rate of the comp the sound track will always be the 94 minutes long even if you set the comp's frame rate to 10 fps or 99 fps.
Your original image sequence 141,000 frames (94*60*25). Your After Effects preferences are set to interpret image sequences as 25 fps.
When you import the image sequence the total time of the image sequence is 94 minutes. Here's an image sequence that I have imported with the interpretation set to 25 fps in my preferences.
Notice that it is five seconds and ten frames long. Now I change the interpretation to 24 fps:
Now the footage is five seconds and fifteen frames long.
There are still exactly the same number of frames, when I render the footage as an image sequence there will still be the same number of frames. The only difference between the the first and the second image sequence is in the length of time it will take to play them back when you set the playback frame rate of the device, which is in this case the composition settings in After Effects. When the comp is set to 24 fps it will take 0.20833333 seconds longer to play back than it would if the comp and the image sequence were both set to 25 fps. After five seconds the audio would be 5 frames out of sync in the 24 fps comp so to keep the audio in sync I would have to slow it down. I would do this in Audition without changing the pitch to put the audio back in perfect sync.
If you change the import settings in your AE Preferences from 25 to 24 fps then when you import your image sequence it will be interpreted as 24 frames per second.
When you check the info instead of being 94 minutes long, when you check the info in the comp panel it will be 97 minutes and 22 frames long so if you put it in a comp that is set to 24 fps it will take 3 minutes and .8 seconds longer to play back. To keep the audio track in sync you will have to slow it down to 96% of the original length. I don't know what DLP software you purchased but most that I have seen will do this audio conversion for you without changing the pitch. If the extra 3 minutes and 22 frames are OK with you and you do not have to apply some changes to the image like color grading the only thing you have to do is change the audio track to keep it in sync. If your DLP software will not do this then you would do that in Audition. There is no need to re-render the image sequence.
If you want to keep the same running time and not change the audio then you just have to drop one frame every 25 frames or use time changing software to blend the pixels together using 1/5 of the motion in the surrounding frames to calculate new pixel positions. You don't do that by changing the interpretation of the original footage, You keep the interpretation at 25 fps but you put it in a 24 fps comp. Now the audio does not need to be slowed down to stay in sync. Unless you know for a fact that the original project was created at 25 frames per second and you have checked the image sequence against the audio track to make sure that AE is interpreting the frame rate correctly the only reason AE is telling you that the image sequence is 25 fps is because your preferences are set to interpret image sequences as 25 fps. There is nothing strange going on with After Effects or your render settings. That's the way all image sequences work and the way they have always worked.
Some software may allow you to add metadata to an image sequence that specifies a frame rate AE does not give you that option. Note the options to include metadata are grayed out.
So there is nothing wrong with your workflow. You just are not understanding how image sequences work. I even checked the Metadata panel in AE and in other software and there is not even a frame rate option in the metadata section of an image sequence that can be read.
Also, you can easily export image sequences from Premiere Pro and render them as 16 bit. Premiere Pro CC 2015 new features summary. Premiere Pro works in Full Float natively.
If your must maintain the total running time then Premiere Pro will handle the dropping a 25 fps image sequence in a 24 fps Premiere Pro sequence (timeline) just fine and it will process the render in much less time. If you can live with the running time change and need to slow down the audio Premiere Pro is also your tool of choice. You would just process the audio track in Audition using dynamic link to slow it down and maintain the pitch. The pitch change is going to be unnoticeable if you just want to slow it down.
If your DCP software will not handle the frame rate change you'll need to interpret the footage as 25 fps and put it in a composition or a Premiere Pro sequence that is set to 24 fps and render a new image sequence that contains 135,360 frames instead of the original 141,000.
Of course the number of tiff frames won't change. In the 25p tiff sequence I have 134.700 tiff images. I know that in the 24p tiff sequence I will still have 134.700 still images. The only difference is the approximatelly 4 minutes longer duration. I don't mind at all for this longer duration. I want it. It makes my films longer and I like that. The only thing I will do is to make the audio channels longer in order to perfectly sync with the video and tweek the audio pitch so the tonality is normal and not distorted.
You mean that I don't have to re-export the tiff sequence so that it is 24p instead 25p (since the total images will be 134.700 eitherway) and just put the tiff sequence I already have directly in the DCP builder along with the new 24p converted audio channels and I am good to go? That would be very good because I will have to wait 36 hours for the new tiff export. I will just import to the DCP builder the tiff sequence I have and I will choose 24fps.
If your audio sequence fits the image sequence you don't have to do anything. If the audio sequence is too long or to short then you can change it in Audition or use time remapping in AE and not worry about the pitch change. 99.9% of all people will not detect the pitch change. I don't know what software you are using so I don't know if it has the option to resample the audio.
The easiest way to check the audio against the image sequence is to set up a 24 fps sequence (that what a timeline is called in Premiere Pro) and interpret your footage (your image sequence) as 24 fps and drop it into the timeline, then add the audio track. Check the last frame and see if the audio matches up. You can also do this in AE.
Once again, the only reason that your image sequence is interpreted as being 25 frames per second is that is what your preferences have been set to. You also have preferences in Premiere Pro. Unless you have information from the person that rendered the image sequence or you compare the image sequence to the audio track you have no way of telling if the frame rate of the image sequence is correct.
This is not brain surgery. It isn't rocket science, either:
- Import your image sequence.
- Highlight the image sequence in the project panel.
- Go File>Interpret>Main.
- Change the sequence's frame rate to whatever you want.
- Drag the footage onto the Make Comp icon at the bottom or the project panel.
- Export or Render according to your wishes.
That is IT. You're done with your video. Use Audition to fix your audio.
Just to clarify, if you are not adding any effects or changing your image sequence in anyway there is no reason to re-render it.