25FPS and Footage — How?

[Dan Pinder]

I am modifying a spotting notes database to be able to use PAL video. I can enter my data in F+F or in TC but I want to output the notes in 25FPS TC.

For you PAL-Post peeps, on a video burn-in, does 1+08 equal 24FPS or 25FPS? Perhaps if I understood how you guys do your telecine, it would tell me how to proceed. I've read in the past about various types of speed-ups and complicated pull factors. How do you do Telecine? Is it frame-for-frame and that the video slows the film down by 4.xx% or something?

[José Luis Díaz]

Hi Dan,

"How do you do Telecine? Is it frame-for-frame and that the video slows the film down by 4.xx% or something?"

It is frame for frame. So, a video frame corresponds to an only film frame. Each video frame has only two fields (as in NTSC).
I will try to explain what happen in the feature film format where it is shot at 24fps in the set.

After developed the neg is transfered at 25fps (so the film is not slower buy speedy a 4%), where each film frame is spreaded in only one video frame of two fields).
From this point Avid and FCP has two different paths. Both (Avid and FCP) digitize at 25 frame per second.
But Avid duplicate a field each 12 frames. So, Avid generates two extra fields (one frame) per second, meaning a full frame per second. This is the amount of image length you need to conserve the synch relationship with the sound.
Because sound speed is unaltered by Avid.

FCP has a different point of view. FCP digitize at 25 fps (50 field per second - a very regular PAL video signal) as Avid but, thanks to alter some maths into the QuickTime movie, you can alter the speed of the image from it digitized 25fps to 24fps. In this way, each frame stays in the screen 41.66667 milliseconds (at 24fps) instead of 40.00000 milliseconds (when run at 25fps).

Wait a minute, my english very limited. May be, if you download Apple's CinemaTools Manual you will read in a better english than mine all this concept. Pages 25, 26 and 144.

Good luck, Dan.

José Luis Díaz

[Dan Pinder]

That's massively helpful—thank you.