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.

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.

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.

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... ;)

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.

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

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.

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.

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?

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.

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.

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.

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... :)

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.)

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.

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.

Somehow things have become switched around in this discussion - 60i produces smoother motion, not jerkier, and (depending on the cameras in question) may have less detail than true progressive footage. With 60i you are trading off some vertical resolution (I believe it's approximately 30%) for greater temporal resolution - 60 samples per second versus 24.

Next time you're watching a movie (24p) in a theater and there's a shot panning along with a character or vehicle, try focusing on something other than the main subject - maybe the sides or corner of the screen. If you've never done this before you'll be blown away by how badly the image is stuttering there. Now try the same thing while watching a football game on a CRT television (60i) - no stutter, just smooth motion.

The higher temporal resolution of 60i more closely approximates what the human eye sees, and thus may appear more 'realistic', while the subtle stutter of 24p may tend to distance the viewer from the material a bit. I think the biggest difference though is one of conditioning - most viewers have a lifetime of associating the smooth motion of 60i with newscasts, sports, soap operas, reality shows and home videos. Likewise, the stutter of 24p is associated with movies and high production value dramatic television. This isn't necessarily a conscious awareness - most people wouldn't look at something and say 'that looks like 60i', but most can say 'that looks more like a movie' or 'that looks more like a home video'. 24p isn't a magic bullet in terms of making your video look a 'real movie' - but it's certainly an important piece in a puzzle that also includes lighting, staging, acting, sound, etc.

Actually, this is not what's happening with interlaced video. Interlaced video isn't meant to be played back with the two fields displayed simultaneously with an offset from each other. On an interlaced display (a crt television) each field is displayed one after the other so the mind is basically seeing 60 discrete half resolution frames. If you're seeing offset lines and noise in 60i footage it's because you're watching interlaced video on a progressive display (i.e. an LCD or CRT computer monitor) and the playback software/hardware is incorrectly displaying the pairs of fields simultaneously - instead of either dropping one field, blending the fields together, or scaling each field to full frame and playing it as 60p.

This is what I meant when I said the words mean different things to people.

The "jerkiness" I'm talking is not the strobing or studder of slower frame progressive display. I'm talking about what's happening within the picture. It's more noticeable to some than others. As one half resolultion frame is displayed after the other, with moving objects, perhaps an arm waving, each half resolution frame is offset from the previous.

Meanwhile, the mind is trying to put together a complete picture. In some people there is a "jerkiness" or "shimmer" (again a misleading term) or other distraction. Some people see it and some don't.

On a progressive display, the offset is easily seen since both half resolution frames are displayed at exactly the same time. However, it is still there even if the frames are displayed (normally) one after the next, but not as obvious. On a CRT, since the images remain a moment after they are put on the screen, in effect, both fields are appearing simultaneously, as well as non-matching fields are appearing together, as the second field of one frame and the first frame of the next are seen.

There is a difference in how different people see this. I'll refer once more to interlaced computer monitors. Some people aren't bothered, and others can barely used them.

I like Chris Hurd's answer the best,
sports: 60i
wedding: 30p
narrative: 24p

The 60i will give the most detail and smoother action because of the higher frame rate, though interlaced. 60p would probably be even better.

For the wedding, the 30p would take the edge off the reality show look of the wedding but still leave a little leeway to do video style camera work.

For the narrative the 24p would give the look people are used to and probably adds a bit of timelessness. However, rules for camera work are a bit stricter in some regard.

It all doesn't make much difference unless it is applied to actual video, so I will quit and go back to work.

That's correct, the persistence of the phosphor on the CRT face helps create a full frame from two fields even though they aren't displayed simultaneously.

You keep mentioning interlaced computer monitors but virtually all computer monitors I'm aware of in this day and age are progressive.

To Mats: 24P came about as an acceptable trade-off between the illusion of continuous motion (more so in a darkened theater because the iris of our eyes opens up and creates 'persistence of vision'), and the higher cost of running film through the camera faster. To help with the 24P illusion, they have a mechanical shutter on the film camera that rotates and exposes each single frame twice, effectively doubling the frame rate. So each exposed frame has two instances of the image at 1/48th of a second differential. When projected back in a theater, the mechanical shutter on the projector flashes each frame twice on the screen so you effectively see 48 images per second, not 24.

With video cameras, the ability to shoot at 24 frames per second with a shutter of 1/48th helps create the same cadence and motion blur of film. But as has been stated by others, this is just one piece of the puzzle in making video look less like video and more like film. Adding gamma curves to video cameras that behave like film stock is another part of it.

Hope this helps,

-gb-

Greg, OK - It's time for me to put theory into practise. Will be interesting to test 50i and 25p/25F for the next concert.

The only point was that they bother some people and not others... though the interlaced monitor doesn't really exist anymore.

Just as some find flourescent lights very uncomfortable and others don't.

I think there is a significant variation in the way people perceive some types of motion.

Document describing different modes
 

Hi

Maybe a little off topic, but here is a link to a document describing the different modes, interlaced, frame and progressive. I'm not shure that the fram mode in XH-A1 is done as the document describes as Canon doesn't specify how their frame mode is done, but as there is a drop in resolution one can jump to conclusion that the frame mode in the A1 is done that way.

ftp://ftp.panasonic.com/pub/Panasoni...ressive-WP.pdf

A little note concerning film to PAL transfer. As there is so small difference between film, 24fps, and PAL, 25fps, the conversation is done by just speeding upp the film to 25fps. That's why films allways are 4% shorter in length in PAL countries. The small difference in audio pitch is not noticeable.


Regards,

/Bo

One thing I haven't seen mentioned in this thread is the advantage that shooting in progressive mode (24, 25, 30, etc.) means for VFX work. Much easier to work with progressive footage for most VFX jobs.

I just shot my latest wedding in 24F, and I think it looks spectacular. I wanted to go with 30F, but the lighting in the church was so bad that I needed 24F to keep gain down to 6db while still getting a usable picture.

I'm one of those people who is bothered by interlaced monitors (especially when people leave them set to 60 Hz) and fluorescent lights, so the frame rate of video is readily noticeable to me.

My B roll for the wedding was shot in 60i and had to be converted to "almost" match up with the 24F footage. Color aside, the 60i footage has that "live, you-are-there" look to it, while the 24F footage emulates the feel of film and gives the client something that "Uncle Bob's" camcorder can't give them. Plus, stills grabbed from 24F are MUCH better. 24F provides a more intimate look, which is ideal for a wedding video.

I suppose SFX work in frame mode would be easier as well, but I haven't had time to "play" with the A1 yet. I thought I'd get the chance with the DV Challenge, but I'm a bonehead and missed the posting of the theme.

I made some tests (connecting the A1 to a plasma via component) on 25F compared to 50i. Paning in 25F cause a "studdering" or "strobing" effect on the background. 50i is smooth as you would see it with your own eyes. Is this smooth movement what some refer to "video-ish" and the more jagged as "film-ish". With this small test I must say that 50i is superior, but it is *not* a complete test so I might reconsider when tested more.

I suggest you set the camera up, don't move it, then sit in front of it, walk around in front of it, jump up and down, skip rope and run by it. You will see more the differences this way.

Fast panning is not something done with 24p, and it will show the strobing effect. With 24p/25p you want to follow an object when panning to hide the background strobing. The short DOF in film also helps to hide this.

However, movements inside the frame look fine, but different with 24p than interlaced video.

Another comparison you could make would be the stage sequences in the Altman film The Company -- compare these with a broadcast stage presentation of a ballet or dance performance. The lighting is still different, but similar enough to compare the motion. The Company was shot with progressive video and transferred to film.

An excellent example of how video looks is the Korean soap operas. (Perhaps in Europe you have the Mexican soaps.)

Jack, using 25F/50i how would you estimate the fast moving hands of a pianist to be? I assume - not tested yet - that the 50i might have the interlace artifact. In this (pianist) case the background does not move at all, but the hands in the center of the image move all the time, and alot, and quick.

Mats, you are learning why using 24/25P demands special camera techniques. If you want to shoot this way, you have to approach it more like a film camera operator would. Learn those techniques, and you'll be well on your way to understanding what does and doesn't work.

Also, remember what I said about a darkened theater? Too many people these days try to watch 24P in a bright room and it looks more strobe like. Review your 25P in a darkened room after your eyes adjust and see if it looks better. And, when you shoot 25p, don't use 1/25 shutter speed... double it to 1/50 just as 24P uses 1/48th.

Have fun and keep learning!

-gb-

Interlaced video (50i) will look fine when viewed on a TV. Viewed on a progressive computer display, you will see the interlace lines.

Practically speaking, fast actions can be captured well with both 24p/25p progressive and 50i/60i. The difference for the operator is in the types of camera work that can be done.

For the viewer, if the camera operator does his job properly, the viewer will see what can only be described as somewhat vague and philosophical differences in the quality of the motion and the emotional experience (together with the lighting and other aspects of the video) the video evokes.

Taling too much about something quickly becomes an excuse for not doing something.

You serious? The difference is huge!

Greg, while I agree in general with your points, I believe it's not necessary to use the 1/48th shutter speed in order to "effectively see 48 images per second, not 24". You can achieve the same when watching each frame more that once; the modern plasmas do it by displaying the 25p (PAL) material with refresh rate being a multiple of 25, e.e. 50 or 100 Hz. Also, some can sense the 24fps candence and swith the refresh rate to its multiple, like 72 Hz (the Kuro line by Pionner) or even as high as 120 Hz.

This lets you avoid flicker while staying synchronized with the actual fps.

The stiff rule of shooting only with 1/48th (1/50 for PAL) deprives the 24/25p mode user of a very nice bonus of the 1/24 (1/25th in PAL) shutter speed: a full stop more exposure, so important in those HDV camera in low light situations!

With my V1E, I almost exclusively use 25p with 1/25th for church events (not just weddings, but also music performances etc). This lets me stay safely below the 9dB gain needed in those notoriously dim surroundings (anything higher than 9dB is unacceptable for the V1e's progressive mode). I'm very satisfied with the picture I'm getting (of course, there is not much movement involved, which helps in keeping the 25fps stutter- and blur- free a lot).

While it is obviously possible to shoot with a 1/24 shutter, it will create a motion blur that has to be evaluated to decide whether it is a worthwhile tradeoff for the extra stop. I've done it myself and sometimes regretted it when I see the results. Certain scenes in "Apocalypto" were shot this way and a sharp eye can discern the difference. If one is truly hoping to emulate the film look, it's best to avoid as the resulting motion blur is a detriment.

Indeed, that is why the default 24p shutter speed on the Canon XH G1 and A1 is 1/48th.

Chris, it's 1/25th on my V1E, and - if I remember correcly - it also was 1/25th on the Canon I tested. This is basically like switching the shutter off (shutter=fps; just a single full exposition per frame), and we discussed it in the new EX camera forum.

So, I guess both Canon and Sony meant exactly what I have said.

Sorry, but this is one difference between 24p and 25p on Canon camcorders. While it's true that the default 25p shutter speed is 1/25th, it is in fact a different story in 24p. For both the Canon XL and XH camcorders, the default 24p shutter speed is indeed 1/48th.

No, I guess they did not, at least as far as 24p is concerned. See the posts from Greg Boston and Charles Papert above. Hope this helps,

Fair enough - I never had an opportunity to lay hands on an NTSC machine. From what you're saying, the EX will probably default to 1/48th with shutter off in the 1080/24p or 720/24p modes.

The 1/25s default on PAL cams has to be a mistake on Canon's part. Most footage with any significant motion shot at 1/25s has far too much motion blur. It should be a special effect setting, not the default (my opinion, of course).

Richard

Thankfully the default shutter speed is easily changeable; as far as Canon camcorders are concerned, it's an annoyance only in the XL series. In the EVF there's a small red warning LED that shines anytime the shutter speed is out of default, and there's no way to turn it off. It's just something you have to learn to ignore.

Respectfully, let me disagree - while it's way too slow in 50i and causes "special effect" blur indeed, in 25p (provided the subject is reasonably stationary, or you only pan following your (focussed) main subject), it can give very nice picture with that a bit 'dreamy' feeling about it... As stated before, I only use it in dim surroundings and with not too much movement.

Can you post any clips showing the huge difference?

It may or may not. Canon chose to make the 1/48th a default because they knew that the users shooting in 24 wanted to achieve a film look with the correct motion blur.

However, if the EX provides a shutter on/off like the larger cameras, then simply turning on the switch might land you somewhere else (my F350 tends to remember your last shutter speed used). Anytime I use 23.98 on the F350, I have to manually check and adjust, if necessary to get 1/48th shutter when the switch is turned on.

I certainly can understand you wanting to use 1/25, or full frame shutter rate in low light. It's an aesthetic choice you make to avoid gain or having the iris wide open. But you have to know going in that motion blur is going to be a problem and movement within frame must be kept to a minimum. I just love the 64 frame accumulation on the F350... it turns night into day but there can be no movement. Works good for time lapses though.

-gb-