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Old June 30th, 2006, 07:22 PM   #1
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key question regarding multiple frame rates!

Hello,

Can anyone please tell me if when you record in 720p/24 native progressive mode and overcrank at 60fps, how much time do you have on an 8GB card?

I read that an 8GB card gives you 20 minutes in 24 fps, 16 at 30 fps and 8 at 60fps.

But if your set speed is 24fps but you are overcranking at 60fps for slow motion, does that mean you still have 20 minutes or is it just 8 minutes on an 8GB card?

Thanks very much in advance,

- Nicholas
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Old June 30th, 2006, 07:39 PM   #2
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Quote:
Originally Posted by Nicholas Natteau
Hello,

Can anyone please tell me if when you record in 720p/24 native progressive mode and overcrank at 60fps, how much time do you have on an 8GB card?

I read that an 8GB card gives you 20 minutes in 24 fps, 16 at 30 fps and 8 at 60fps.

But if your set speed is 24fps but you are overcranking at 60fps for slow motion, does that mean you still have 20 minutes or is it just 8 minutes on an 8GB card?

Thanks very much in advance,

- Nicholas
Being set at 24pN [edit: typo fixed] or 24p and 60p are mutually exclusive.
[edit: Not that that's what you asked...sorry for misunderstanding you at first...]
24pN is the only 24fps flavor that gives you the storage boost, since you're truly recording only 24 frames per second. 24p and 24pA both actually record 60 fps, and flag the pull-down routine. You'd have to get your edit system to ignore that pull-down flag on ingest to get the overcrank effect. I don't have any experience trying that.
[edit: see posts below to clarify the dumbass thing I just wrote without proofreading it! I blame it on being really hungry...]

My recommendation would be to shoot at 720/24p @60fps for your overcrank scenes, then go back down to your preferred flavor of 720/24 for the remainder of your footage. Just test your edit system to make sure it'll bring 60 into a 24p timeline as slomo. My hunch is that'd be easier than shooting 24 over 60, and asking the editor to ignore the 24 flag.

Robert Lane has probably tested this thoroughly, though perhaps not with your edit software (which wasn't described).
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Last edited by Scott Auerbach; June 30th, 2006 at 11:14 PM.
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Old June 30th, 2006, 08:37 PM   #3
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Quote:
Originally Posted by Scott Auerbach
Being set at 24pN or 24pA and 60p are mutually exclusive. 24pN is the only 24fps flavor that gives you the storage boost, since you're truly recording only 24 frames per second. 24p and 24pA both actually record 60 fps, and flag the pull-down routine. You'd have to get your edit system to ignore that pull-down flag on ingest to get the overcrank effect. I don't have any experience trying that.
Ummm, not quite Scott. The Pana and my Sony F350 record a true 24fps in normal 24p mode. In overcrank, both cameras record 60fps and then play back the resulting footage at 24fps which gives a smooth slowmotion effect. That's what those modes are for.

They aren't 'always' recording 60fps as that would be extremely wasteful of the capture media, be it tape, card, or disk.

The numbers Nicholas mentioned are about right. If you overcrank, you are going to get less running time just as you would by overcranking a 400' mag on a real film camera. If you undercrank, you'll get longer than standard 24p would give you.

Pulldown flags are only necessary when the playback and receiving device (say your camera's video out to your tv) don't match. Your NTSC tv has no idea what to do with 24p so the camera has to convert it to 60i.

You can author a true 24p DVD (which also give you more running time than 60i) and the DVD player will apply the pulldown conversion for your tv set.

regards,

-gb-
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Old June 30th, 2006, 10:49 PM   #4
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Well I sure botched that one... a typo, something really poorly worded, something misunderstood, and something downright wrong! But I did get one thing right...

So far, I'd only used variable frame rates through 720/60 ... I didn't realize until I just now checked, that you can also get them through 720/24. Of course, it makes sense that that's the only way to overcrank (which I obviously hadn't done yet... I'd been playing with undercranking.) Score one for the "D'OH!" team. I clearly hadn't worked through all the menu settings.

On the other hand, Greg, 720/24p IS actually recording 60 frames, and flagging the pulldown. Really.* You can see this yourself by setting the camera to 720/24p and checking the available duration on an empty card. My 8GB card has 8 min of recording time when set at 720/60p at 60 fps. Ditto when set at 720/24p mode, 24 fps frame rate.

When I switch to 720/24pN mode, 24 fps frame rate, the duration jumps to 20 min. 720/24p ~really is~ 24 over 60. That's the difference between Native mode and just plain progressive mode on the HVX200.

In fact, whether you're set to 720/24p or 720/60p, and no matter what your frame rate is, you only get 8 min on an 8GB card. Your only space-saver on the card is to record in pN mode. I also see now that pA is only available in 480 and 1080, not in 720. My bad.

As for pulldown flags, they're used by the camera when it plays non-Native mode footage out the video outputs. They're used in the edit system, too. It's not just a TV set thing.

I don't know anything about the XDCAMs... their 24p might be 24pN all the time. The Varicam (which the 200 is based on) records 60p all the time, and flags the pulldown. Otherwise it'd have to change tape speed for each frame rate, which no tape camera does. A 32-min DVCProHD tape is 32 min, no matter what frame rate you're using. The tape runs at 4x the speed of DVCPro, all the time.

So... my apologies, Nicholas, for my totally boneheaded response. Have we completely confused you yet? Is it time for Godzilla?

What I SHOULD have said is to be in 720/24p or pN mode for the regular footage (I'd go with pN, since it does save space), and shoot 60 fps in 720/24p mode for the overcrank. Since you're shooting 60fps, it doesn't make any difference whether you're in 24p or 24pN. Gee.... did I say it right this time??

And yes, Nicholas, your figures were correct. In Native (i.e., 720/24pN) mode, you get 20 min on an 8GB card at 24 fps, but only 8 min when overcranking at 60fps.

*check out page 5 of Panasonic's B_AG-HVX200.pdf brochure.
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Last edited by Scott Auerbach; June 30th, 2006 at 11:20 PM.
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Old July 1st, 2006, 12:45 AM   #5
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follow up

Hi Scott,

Thank you very much for taking the time to explain that to me.

Everything is clear to me in your second post! Thanks!!!

So if I understand correctly then, you get 20 minutes on an 8GB card, only if you shoot 720/24 progressive native.

But even if you remain on that setting (24pN), you can only shoot 8 minutes, if everything you shoot is overcranked at 60fps.

By that same token then, if you remained in 24pN but were undercranking at 12fps, would you have up to 40 minutes on an 8GB card???

In conclusion then, it sounds like overcranking at 60fps in 720 / 24pN mode is like shooting in 720/60p...you get only 8 minutes on an 8GB card. Correct????

Thank you very much in advance,

- Nicholas
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Old July 1st, 2006, 02:12 AM   #6
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Quote:
Originally Posted by Nicholas Natteau
Hi Scott,

Thank you very much for taking the time to explain that to me.

Everything is clear to me in your second post! Thanks!!!

So if I understand correctly then, you get 20 minutes on an 8GB card, only if you shoot 720/24 progressive native.

But even if you remain on that setting (24pN), you can only shoot 8 minutes, if everything you shoot is overcranked at 60fps.

By that same token then, if you remained in 24pN but were undercranking at 12fps, would you have up to 40 minutes on an 8GB card???

In conclusion then, it sounds like overcranking at 60fps in 720 / 24pN mode is like shooting in 720/60p...you get only 8 minutes on an 8GB card. Correct????

Thank you very much in advance,

- Nicholas
That's what I call 'fixing it in post.' <wince>

Correct in both cases. 720/x pN (x=either 30 or 24) records only the frames @ the selected frame rate.

Assuming I'm understanding what I've read (I haven't tested this in an edit system): the (x) value just flags the playback device (camera or edit system) as to what the playback rate should be. In other words, 12 fps recorded in 24pN mode will play back 2x undercranked. 12 fps recorded in 30pN mode will play back 2.5x undercranked. The file size is identical, since it's only capturing 12 frames per second of real time. But the playback rate changes depending on whether it's marked as 24 or 30. You can think of the mode rate (24pN or 30pN) as being like the project frame rate on an Avid or Final Cut timeline.

If you want to think of it like music, 24pN or 30pN is like a metronome... it establishes the rate at which each bar of music gets played. Against that, frame rate is like the number of notes in each bar. If we say 12 fps is like 12 notes in a bar of music, then changing the metronome rate makes the music play faster or slower, even though the bar always has 12 notes in it.

In the Panasonic Varicam, since tape speed is a constant 60p, when you shot at 6fps and played back the tape, you'd get 10 frames of a still image, then another 10 frames of a still image, etc. To get the "fast-mo" undercrank effect, you then processed the footage to run faster (in essence, deleting all the redundant frames in post). Or you could leave it as is and get a nice stutter-freeze effect that worked well with a slow shutter speed (each frame was nicely blurred). That's exactly what happens in the HVX in 720/60p mode. If you shoot at 12 fps in 720/60p, you get 5 still frames, followed by another 5 still frames.

The opposite is true with the HVX in pN mode: it records ~~only one frame at a time at the selected frame rate,~~ and the playback rate is the "mode" rate. Any time your frame rate doesn't match your mode rate in pN mode, you automatically get slomo or fast-mo.

To get a Varicam-like kind of stutter-freeze effect in pN mode, you'd have to slomo it in post with a "duplicate each frame" slomo (as opposed to something like Avid's Timewarp, which creates artificial inbetweener frames).

You get exactly the same stutter-freeze look with 12fps in 720/60p ...OR... 12fps in 720/30pN and doing a slomo in post with frame duplication... In the first case, no processing time in the edit suite. In the latter case, more room on the P2 card due to smaller file size.

Don't forget that you still have shutter speed control in variable frame mode... it's in degrees (like a film camera) instead of fractions of a second, but you still have control... at 12fps, your effective shutter speed can be as low as 1/12 sec, or as high as you want. If you want good, crisp slomo at 60fps, you should light your scene bright enough to use a shutter speed under the default 180 degrees (180 degrees = 1/2 of a full 360 degree shutter travel... in other words, 180 degree shutter at 60 fps = 1/120th sec shutter speed. 90 degrees would be 1/240th, etc.) Tests are always a good idea. Sometimes slomo looks better with a touch of blur in each frame...if you're shooting with something like a 10 degree shutter, everything is going to be so tack sharp that it may seem strobe-like on playback. We've all seen that look... the slomo shot of fruit splashing into a bowl of water, with every speeding drop tack-sharp in mid air... It's cool, but seems somehow unnatural. (Those scenes are often actually shot with specialty strobe arrays, synced to flash in tandem with the film camera's shutter. Sometimes it's the only way to get enough lumens to have that fast a shutter speed AND depth of field without blowing the entire building's circuit breaker.)
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Last edited by Scott Auerbach; July 1st, 2006 at 02:48 AM.
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