24 Speed Question

[Barry Green]

The real 24p cameras run their CCDs at 24hz, capturing 24 distinct frames per second, just like a film camera does. They don’t try to reverse-extract frames out from a higher-frame-rate capture, because that would be bogus (like CineFrame 24 on the FX1). Instead the capture 24 distinct individual frames per second.

The HVX has the capability to record just those frames, when in 720p mode. All the other cameras have to (and the HVX in 1080 mode has to as well) conform the 24 frames into a 60i data stream. But that’s a process of adding fields, just like when you transfer 24fps film to 60i video. Nothing bogus happens, it’s a well-established workflow. 2-3 pulldown is introduced to round the sequence out to 60 fields per second.

[doka15] “So no real video camera records a true 24 smooth P like a film camera, right? I am not exactly sure about this that is why I am asking.”

All the true 24p cameras acquire a true, smooth, 24 progressive frames per second.

—————–
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[Graeme Nattress]

When, say, the DVX10 shoots 24p, the CCD and DSP etc. are all running at 24 frames per second, exactly the same as film – the motion is the same. 3:2 pulldown gets added, just as it would in a telecine, and recorded to tape.

So no, the camera is not still shooting at 60i or 30p. That’s what Sony does and that’s why CF24 on the FX1 or Z1 looks so bad.

Graeme

– http://www.nattress.com – Film Effects and Standards Conversion for FCP

[Lars Wikstrom]

I see. So the advanced 24p (Hvx200) will lay down a true 24p to the P2 cards since it is really shooting 24P, not pulling them from 30p. That is good news then and I can see why the HDV cameras are worse now.

My second questions it this. Is it True 24P or is it a 24P drop frame which is 23.something? So if I wake up one day and say. I want to shoot a film and transfer it to film to play in theaters I switch it to 24P. Or I wake up and say I want to shoot a film that will air on TV and flip a switch to 23.967 (not sure about that number) to match video drop frame so my audio will sync up.

Is the camera 1 or the other or both?

Thanks again.

-Lars

[Graeme Nattress]

Drop frame is timecode – it does not refer to frame rate, which for NTSC video is always 29.97fps or 23.98fps. Film is 24.00fps.

You’d not want to shoot 24.00 even if it were available because you’d not be able to display it on your monitor properly.

Graeme

– http://www.nattress.com – Film Effects and Standards Conversion for FCP

[Lars Wikstrom]

So the HVX200 cameras do shoot at 23.98fps so they are compatable with NTSC 29.97. So, shooting with these cameras with the intension of transfering to film stock you are still shooting at 23.98? Correct?

So during Transfer to film is the Video footage sped up to 24fps from 23.98fps? or is it left at 23.98 and transfered to film that way?

I know they don’t just play the the video and transfer to film. Every video frame is scanned to a film frame. I’m just wondering how they do the transfer with miss matching frame rates and audio sync.

Thanks,

-Lars

[Graeme Nattress]

[doka15] “So, shooting with these cameras with the intension of transfering to film stock you are still shooting at 23.98? Correct?”
Yes. They shoot at 23.98fps.

[doka15] “So during Transfer to film is the Video footage sped up to 24fps from 23.98fps? or is it left at 23.98 and transfered to film that way? “

Yes, it’s sped up from 23.98fps to 24.00fps. The audio is similarly sped up slightly.

They transfer frame for frame, and the audio gets slightly sped up. The reverse is done for transferring film to video.

Graeme

– http://www.nattress.com – Film Effects and Standards Conversion for FCP

[Barry Green]

The speed difference between 23.976 and 24.000 is 1/10 of 1%. When a DVX or SDX or XL2 or other 24p camera is transferred to film, it’s done frame-for-frame, and yes the audio would probably need to be adapted/stretched as well. Presumably the HVX will also run at 23.976. HDTV in the USA is based around the 59.94 clock rate, which is 0.1% slower than 60hz; since the HVX is ATSC and NTSC-compatible, it’s only reasonable to expect that it will also be 59.94hz & 23.976hz.

—————–
Get the most from your DVX camera. The DVX Book and DVX DVD are now available at https://www.dvxuser.com/articles/dvxbook/ and at Amazon (https://www.fiftv.com/db)

[Lars Wikstrom]

Thank you, that helps to clear it up. So there is no 24p it is always a 23.976 so it is NTSC compatable. I would hear people saying 24p and 23.976 and they are one in the same from what I gather here.

Thanks you.

-Lars

[Graeme Nattress]

24p = 23.98fps progressive video
30p = 29.97fps progressive video
60p = 59.94fps progressive video
60i = 29.97fps interlaced video (or 59.95 fields per second interlaced video)
film = 24fps or 24.00fps to make it clear what you’re saying, when talking also about 23.98fps.

I just wish they’d have fixed NTSC back to 30fps rather than 29.97fps with the advent of HD. It would have made archive programs run a little fast, giving you an extra second of adverts too!!

Graeme

– http://www.nattress.com – Film Effects and Standards Conversion for FCP

[Tony]

Gramme,

I think we need to be very specific when referring to the HD frame rates instead of rounding.

For example

24P can actually refer to 23.98 or 24.00
30P can actually refer to 29.97 or 30.00
60P can actually refer to 59.94 or 60.00

I have found that most of the confusion involved in 24P is caused by using the frames rates generically and not being specific on the exact hz rate.

In the field it is absolutely essential that the camera crew and sound crew are aware of the specific frame rate chosen at the camera because the implications of a mismatch creates problems later in post ie- camera at 23.98 sound at 30.00 instead of camera at 23.98 sound at 29.97 which is the proper correlation.

The frame rates without zeros are the rates to use when dealing with a NTSC editing workflow.

Tony Salgado