Ultmately dumb question: What is 24f for? at DVinfo.net

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Old August 25th, 2007, 11:30 AM   #1
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Ultmately dumb question: What is 24f for?

I have never been requested to shoot 24f, and never had the chance to experiment myself. But I see people here discussing it all the time. My uneducated guess would be for transferring the 24f video to 35mm movie film so there is no telecine process needed. Other than that I don't know what the benefit for shooting 24f, oh, maybe saving 6 frames per second to give more bitrate to each frame? Why people keep saying that 24f has more film look? If a movie film is shot in 30fps it still looks like film right? Anyway, I know 24f/p feature in video camera is a big sought-after thing. If
someone can give me some education I really appreciate it... thanks in advance.
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Old August 25th, 2007, 12:07 PM   #2
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Never found a perfect answer myself, other than I assume that the NTSC 30fps rate in USA is inferior to the 25 fps in PAL Land so hence 24F looks more film like, if used to NTSC rates. I have not seen any big diff. between 24F and 50i myself. Perhaps I'm not looking at the correct details. "Film look" is not dependent on fps but much more like lights, lenses, the ever-so-popular 35mm format (see various posts on the adapters) etc. etc.
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Old August 25th, 2007, 02:51 PM   #3
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There are a couple of reasons for using 24p. First, when combined with a wide aspect ratio, good composition, good lighting, good camera moves, the proper camera setup, etc., it does help make the vide look less "videoish."

Second, if you're doing DVD or web encoding, 24 is 20 percent less than 30, so it uses up less data space, which might be significant sometimes.

Third, no pesky deinterlacing artifacts when exporting from your edited timeline (assume you edit in a 24p timeline). You get a cleaner QT for DVD encoding.

I personally wouldn't buy a camera with 24p as the overriding feature. The fact the XH A1 had it was sort of a bonus for me, and once I started shooting 24p, I do like it. However, for the "look," you could do that with software if you wanted, although I have to admit the pulldown thing that happens when you convert 60i to 24p doesn't look as smooth, to me anyway, as real 24p shot in camera.
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Old August 25th, 2007, 03:27 PM   #4
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Bill, is this from US perspective since you have 60i? You should try the PAL version and see what 50i/25fps does in this respect.

Give 25fps (50i) - what would you say is the cons. with Canons 25F and what one should consider when using 50i or 25F.

I've read something that rapid movement of motif will be worse in 25F than 50i. Correct?

BTW, the manual for PAL A1 says that 25F = 25 fps - there is no 24F or 24p, at least given the manual. How they are to match 25 fps with film 24 fps I don't know. Sales trick? As usual the manual says nothing about the subject. If the A1 is as successful as the 350D was (70' per month) one would think that somebody could write a deasent manual or a starters guide. Yeah, "this camera is for pros, they don't need manuals". Right... ;)
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Old August 25th, 2007, 03:44 PM   #5
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Originally Posted by Mats Frendahl View Post
Bill, is this from US perspective since you have 60i? You should try the PAL version
Mats, you should realize that Bill Pryor lives and works in the Kansas City area, which means the majority of the clients for whom he shoots will require delivery in 60i. Therefore it does not make very much sense for him to shoot in 25p or 50i and transcode, adding extra steps (and a quality loss in typical transcoding processes) which are both time consuming and quite unnecessary, especially for someone like Bill who shoots video for a living.

Quote:
How they are to match 25 fps with film 24 fps I don't know.
Actually it's very simple to convert 25p to 24p; it's done all the time in fact.
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Old August 25th, 2007, 04:09 PM   #6
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Chris, the thing here is that the "24" has become - for some at least - an quest for the holy grail.

Some say that it will bring "Hollywood" to your clips. All PAL Land citizens shoot in 25 fps - which is pretty close to 24 - so I guess we all have "film like" footage over here... :) Still, PAL citizens also seem to seek the holy Hollywood grail of 24p. It might be important in US with your NTSC system, that I cannot tell.

Still, Canon do include a 25 fps function on the PAL A1, which is prob. called 24F in NTSC Land. Going from 30 fps to 24 fps might be noticed, but I cannot pin-point the difference in 50i and 25F. Perhaps I simply don't look in the correct places.

The issue was *not* to recommend him to buy a PAL A1 (I'm sure he's efficient enough to judge what to use for his clients), it was to know IF he'd see any difference in 24 vs. PALS 50i/25fps. -- I could very well try a right-side driven Jaguar to find if the engine is the same as the left-hand driven - but I'd never get one if not living in UK, AU, SA, HK, etc.

>Actually it's very simple to convert 25p to 24p; it's done all the time in fact

I'm sure it is - I'd never questioned the technology. If you can make Star Wars/LOTR etc. - 25/24 is a comparably easy task.
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Old August 25th, 2007, 05:09 PM   #7
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I doubt there's any noticeable difference between shooting 24p and 25p. The only advantage would be that 24p could convert to film a little easier; but if you're in a PAL county, all the labs do PAL-to-film conversion routinely with no problems. Seems to me the difference would be in 50i versus 25p, and I think the difference would be about like the difference between 60i and 24p in the NTSC world. The progressive look is a little different from the interlaced look, and you wouldn't have the interlace artifacts when exporting for DVD, etc.

I don't know why anybody fortunate enough to be able to shoot PAL would give a damn about 24 fps, unless your stuff is going to film. And even then, why bother.

I still remember the first time I saw PAL TV, in Greece. It was about as impressive as the difference between our standard definition and HD. I came back to the U.S. wanting to shoot everything in PAL.
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Old August 25th, 2007, 05:31 PM   #8
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Right Bill, It seems like this is most noticeable in US with the NTSC system, although I'd never compared the two. I will however test with 25F compared to 50i on the next concert with a "quick-handed" concert pianist to see if there will be some a) "Hollywoodic improvment" or b) any other result, good or bad. I'll report back - if I find something to report. However, I assume as you say that in PAL Land there is not a big difference.

"you wouldn't have the interlace artifacts when exporting for DVD"

I don't fully understand. Cannot the DVD format handle 50i footage?
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Old August 25th, 2007, 05:38 PM   #9
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The way I do DVDs is export first a full res QT from FCP. If it's 24p footage (or presumably 30p as well), you can see the typical interlace artifacts, which become more noticeable on heavier compressions. Not so much for DVD, although a little. They show up more when doing heavier compressions for web delivery. No such artifacts in progressiveland, as each frame is a discrete piece.
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Old August 25th, 2007, 05:41 PM   #10
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The difference between progressive and interlaced is most obvious on TV shows that shoot in progressive (24p or 30p) then intercut interlaced footage that is shown as if it were a home video. The smoothness seen in the progressive is not there in the interlaced, which is more detailed and "jerky."

Another way to see the difference is to compare a "pre-taped" epsisode of Will & Grace with an episode that was broadcast live. The "pre-taped" episodes are shot on film (I believe at 30fps) and the live broadcast episodes are interlaced video.

The filmed episodes are smooth whereas the videotaped episodes look like home video a bit and don't have the same professional feel. (The acting is actually improved when shown progressive.)

Another comparison can be made with the British sitcoms shot on video and the longer shows (like Foye's War) that is apparently filmed. The videotaped shows have a different quality compared to the smoother, slightly dreamier look of the progressive (and lower frame rate) motion. And note that the British shows are PAL (at lease in the video realm).

50 or 60 fps progressive video may have a character more like 50i/60i, because of the similar frame rate. However, I believe the interlacing also adds a video character despite the matching frame rate.
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Old August 25th, 2007, 06:41 PM   #11
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Originally Posted by Bill Pryor View Post
I doubt there's any noticeable difference between shooting 24p and 25p.
The human eye cannot detect a one frame per second difference in frame rate.

So yes, it is impossible to distinguish 24p from 25p visually.
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Old August 25th, 2007, 06:43 PM   #12
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Jack, trying to sum it up:

Interlaced: More detail but "jerky"
24p/25p: More dreamier look

Is there any disadv. then of 25p regarding rapid movements of the "actor", i.e. will 25p have more difficulty of recording rapid movements?

With "jerky" - do you mean movement, i.e. that Interlaced are inferior of recording rapid movements?

I agree that that shows like Foyle's War is prob. shot with film but the main contributor to the overall quality here I think is in the effort they tend to the production. The lights are perfect. If you look at the Midsomer Murders (another alleged high-quality UK series) they have extremely poor lighting, almost close to "movies" of an entire other concept with equally bad acting as the lighting... :) I can only remeber certain episodes of Columbo have such bad lights as Midsomer M. - and Col. was prob. filmed... :)
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Old August 25th, 2007, 06:46 PM   #13
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The human eye cannot detect a one frame per second difference in frame rate.

So yes, it is impossible to distinguish 24p from 25p visually.
Chris, so the "only" advantage of 25p compared to 50i would be that it is 25 *full* frames/sec. instead of interlaced?

(For NTSC Land I guess there is both gain in the "p" and the slower frame rate.)
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Old August 25th, 2007, 07:08 PM   #14
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Other folks might disagree, but in my opinion there is no clear "advantage" of one frame rate over another unless we're talking about specific types of shooting situations... interlace is right for some, progressive is right for others... I think the frame rate should be chosen based on the job at hand.

I would shoot a soccer match in 60i, a wedding in 30p, and a fictional narrative in 24p.

It is an aesthetic choice. The most important thing is that these choices are available.
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Old August 25th, 2007, 07:30 PM   #15
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There's no way to explain in words the differences so that someone else will clearly understand. The words mean slightly different things to different people and people see things differently.

Interlaced computer monitors don't bother some people and they do others. It is likely these people would see progressive and interlaced video differently.

Some people are highly bothered by flourescent lights, and others don't mind them. I expect these people will see progressive and interlaced video differently.

If motion in a British sitcom videotaped and a show filmed lookes the same to you, then there is likely little difference in progressive and interlaced video to you.

Virtually anything shot on film is 24 frames a second, and high action looks fine on these... just look at the Bourne supremacy (the virtually endless closeups and the camera shake are another matter... though they seem not to bother most people and some hate them).

Any video of stage performances, e.g. ballet of a few years ago are taken from film, and they look fine. New ones are probably interlaced video. They look fine, but slightly different to some people.

To me the ultimate example is what I stated above, a TV show, such as Will & Grace, that has episodes both filmed and videotaped. The lighting is basically identical, but the pictures look very different.

With progressive video the mind is simply blending the frames into continuous action. However, with interlaced video, the mind is getting frames where every other line is offset a little, and the mind has to first lineup the offset lines, then blend the frames into video. The result, though is the mind is blending offet frames into motion and the result is that some people get this over active look, almost like there is noise between the frames (which in effect there is, since the lines of the frames don't line up)

Some people will get the effect more than others, just like some people are more sensitive to the flickering of flourescent lights than others.

Also, as stated above, if you are doing work for the web, progressive video eliminates the step of de-interlacing... since web video is progressive.

DVDs can be both progressive and interlaced, so I don't think it's an issue here.

As stated everywhere, the 24p/25p becomes an issue if you are trying to do fast pans and certain other types of movements, when there isn't a foreground object that is being followed.

I also think that shakey-camera work will look better in 24p/25p than in interlaced. I think the interlacing lines will interfere with focusing on the subject and trying to keep it still in the mind.

Again, though, watch a filmed and a videotaped episode of a TV show that is done both ways, and you'll see the difference.

You can also setup a camera yourself in a controlled situation and record similar scenes in progressive and interlaced. Play the tape back from the camera out of the component outs into a monitor. You will see the difference.
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