If a film is shown in the cinema at 24fps, in PAL at 25fps, and in NTSC at 30fps, how many frames per second does the camera take?
And how can an PAL film be converted to NTSC without it running too fast, like what happens when you see old 16fps black and white movies?
You would have to add extra frames to get the correct speed, but where do these frames come from? I could imagine a computer generating them by merging the previous and the next, but what about before computers were so powerful?
Cecil adressed some of your questions in Why is the action in old silent movies so fast?.
In this review, he noted that in some cases the extra frames were created by the simple expedient of duplicating some frames, which may in itself cause some strange effects, but is less annoying than having everyone run around real fast.
In some ways video “frames” are not as discreet as a film frame. With normal exposures the scan line is only at a single point on the screen at any given time.
NTSC is an interlaced standard so you’ll get a field of half the scan lines in 1/60 of a second followed by another field to make the full 525 scan lines in 1/30 of a second.
Depending on the shutter type film frames are not a single frozen point in time as you might think. In the end all the overlapping of frames and scan line fields makes it possible to do film to video transfers without much of a problem.
It’s possible that if all frame rated were the same it would be more difficult to do transfers. film and video frames would have to be perfectly synchronyzed or the effects might be obvious.
That was rather interesting. I knew they could add copies of frames but it would make it jerky, but in modern films I have never seen this jerkiness.
I presume they can record the sound separately and add it back in once they have changed the number of picture frames. Is it just my eye that doesnt notice the 25% difference from 24fps to 30fps, as opposed to the 50% difference from 16fps to 24fps?
thanks both of you
Branney, the real time speed is not changed in a normal 24fps film to video conversion.