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Confused about 24P, 30P, 720P60


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#1 LJ Morelli

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Posted 04 August 2007 - 11:58 PM

I've been shooting standard def for 25 yrs. I do have a working knowledge about what interlaced means, vs progressive. In researching for a new camera I've come across various cameras that shoot in different frame rates, interlaced, or progressive. I'm currently interested in the JVC 200, btw. It's hard to really form my question, but I see 24P, which means what? The camera is shooting at 24 frames per second, and is recording progressively, right? But what's the frame rate?
Now, in 720P60, we're talking about a high def image, 720 lines of rez, with a frame rate of 60, for smoother motion. When we talk about 24P, 30P, etc, why isn't' there a frame rate usually listed.
If 24P, or 30P isn't preceded with a number, does that just mean isn't standard def?

If you're unsure of my question, what would really help me grasp these concepts is for someone who really understands it to please reply in very simple language, as if you're trying to teach someone who has no knowledge what so ever. What's so great about 24P, looks stuttery and jerky to me. Thanks to all in advance, it's driving me crazy!!
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#2 David Mullen ASC

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Posted 05 August 2007 - 08:27 AM

24P, 30P, 60P -- those are frame rates: 24, 30, 60, etc. Just that they are progressive-scan, hence the "P".

Standard def frame rates are 29.97 fps (59.94i) for NTSC or 25 fps (50i) for PAL (there are two fields for every video frame in interlaced scan).

"24P" doesn't indicate resolution, just frame rate in progressive-scan. It could be 24P/480 (720 x 480) or 24P/720 (1280 x 720) or 24P/1080 (1920 x 1080.)

What's confusing is the difference between the frame rate the camera captures images at and the frame rate that is recorded to tape.

For example, you can shoot with the Panasonic Varicam at many frame rates, all progressive-scan, but everything is recorded to DVCPRO HD tape at 60P. So if you shoot at 24P, then 36 redundant frames are added to the recording to add up to 60, since the VTR always runs at that speed.

Many of the HDV cameras either record 60P/720 or 60i/1080, even if they allow 24P shooting. So if it's a 60i/1080 recording, it has to add pulldown to convert 24 "P" frames into 60 fields. (I'm ignoring the European variants which work at 50hz instead of 60.)

As I said, standard def cameras traditionally have been 60i (59.94i) for NTSC, 50i for PAL. So the few progressive-scan standard def cameras like the DVX100 can shoot 24P and 30P (for the NTSC version) but record either to 60i.
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