Thursday, July 12, 2007

24p is in most cases 23.98, or 23.976 or 24000/1001 fps.

Sorry for the weird title, but I have just received that question twice in ten minutes from 48 Hour Film Project contestants. In my last post, I said we are presenting in 1080p24, and we would prefer 24p submissions. The problem is 24.000p is likely not available on 98% of the cameras being entered into the competition (the 2% that can shoot 24.000p are the two Silicon Imaging cameras used by our team -- unless some of the Red guys are entering with a prototype--that would be fun.) The rest shoot what is commonly called 23.98, but I prefer 23.976 (it matters sometimes in AE), but it is really 24000 divided 1001 frames per second or 23.9760239760... So when I said 24p, I really mean 23.976...p -- sorry for the confusion. Even our SI-2K cameras are set to 23.976. 23.976 is the new 24p. Now if you can shoot or edit 24.000, that is fine, too; just never mix 23.976 and 24.0; you get this nasty frame ghosting due to the frame blending in most NLEs. In our more recent software, we pop-up a warning when you add 24.0 to 23.976 timeline (or vice versa.) So if you have a 24.0 camera with a 24.0 timeline, we will re-master it to 23.976 for projection.

Why this weird number : 23.976 (and its direct cousin 29.97?) It goes back to when someone thought it was a good idea to add color to television. They needed to shift the frame-rate slightly so the new "NTSC" color sub-carrier didn't freak out the existing black and white TVs. Now we are stuck with it, and it still works on your mid-century B/W set (but where is the HDMI connector?)

1 comment:

Jonas Hummelstrand said...

So for us lucky enough (!) to be in PAL land, do we shoot 25p and just interpret as 23.976p if we need to deliver to NTSC land?

And if we deliver for digital projection in PAL land, we can use 24.000p?