More concrete info on ProHD

Regarding the JVC "motion smoothing" filter -- I asked Steve Mullen and he says that it is optional, you can disengage it. That's good news.

thisiswells said:
sometimes a cinematographer will shoot a 200 degree shutter for slightly more motion blur and perhaps some may notice it, though to me it is a negligable difference from 180. I understand many Panavision films are shot this way, but I have not been on a Panavision shoot that has to confirm this.
Click to expand...
Film gets shot at a variety of shutter angles, which directly controls shutter speed. Anywhere from around 1/40th to 1/60th is in common use. It all looks like film, but the faster shutter speeds will render crisper motion, with more strobing, and the slower shutter speeds will give you blurrier motion, with less strobing.

Common shutter angles on film cameras include 180, 172.8, 156, and 144 degrees, as well as 200 and 220.

HOWEVER, I am not entirely convinced that todays electronic implentation of a shutter angle actually presents accurate approximation of how that shutter would function in a cine camera.
Click to expand...
There is a potential difference. I postulated on this on 2-pop a few years ago. Basically, in a film camera, the shutter is a rotating disc. In a video camera, the shutter is pretty much a "timer", once 1/60th of a second has gone by, the camera just stops exposing; there is no physical intervention of a physical piece that blocks the light. In a film camera, a rotating disc with a hole in it reveals the light to the film, then blocks the light. In a video camera, the CCD has pretty much an on/off switch, and the duration of how long it's "on" is the shutter speed.

Theoretically (and practically), they deliver similar results. One difference, however, is that because of the way a rotating disc works, different parts of the film frame will be exposed at different times. The way the disc rotates, the upper-left corner would be exposed first, and then more and more of the frame until the entire frame is exposed, and then when the shutter starts to close, the upper-left corner will be covered first, while the lower-right corner would be covered last. Theoretically it could make for a slightly different "look" when compared to a video "shutter", where the entire frame is uncovered simultaneously, then covered simultaneously.

However, as a practical matter, it appears to be basically a non-issue; I split-screened DVX footage shot against film footage, identical footage of identical subjects shot side-by-side at identical moments in time, and there was no discernible difference in motion between the film and DVX footage.

A cine camera simply does not work that way; adjusting your shutter doesn't change your frame rate...
Click to expand...
Well, yes and no. Adjusting the shutter angle doesn't change your frame rate, but changing your frame rate will change your exposure time, and changing the shutter angle will also change the exposure time. So the two are linked. A 180-degree shutter at 24fps yields an exposure time of 1/48, that same shutter at 30fps yields an exposure time of 1/60.

On the DVX and the VariCam, frame rate and shutter speed can be adjusted independently of each other. You can have 24p at 1/1000 if you want, or 24p at 1/24, or basically any rate between 1/24.1 and 1/250.

Shutter angle or shutter speed simply should not affect frame rates -or- the illusion of frame rates.
Click to expand...
They don't, unless you start talking about using shutter speeds slower than the frame rate. You can set any shutter speed when running 24p, without it changing the fact that it's still running at 24p. 1/24 or 1/1000, you'll still be getting 24 frames per second, with the difference being the amount of blur (and the amount of exposure). Same as on a film camera, if you adjusted the shutter angle from 359 degrees (which is impossible) down to 5 degrees or so. It works the same (with the aforementioned difference of a rotating shutter vs. the on/off nature of a CCD).

Now, if you run a shutter speed that's longer than the frame duration, that *will* affect frame rate. For example, if you run 24p with a shutter speed of 1/6, what will end up happening is you'll get effectively 6fps footage on your tape. Each frame is held and buffered until the full exposure is satisfied, and then written to tape, so even though it's writing 24 frames to tape, only 6 of them will be unique, it'll be duplicating five frames during the buffering process.

I think the reason why these little cameras look stroby is due to the fact there is not a proper shutter on them to allow for anything else.
Click to expand...
I disagree. The cameras look stroby due to the way people use them. As mentioned before, when compared against genuine film, at exactly the same shutter speed and shooting identical footage, moving the camera identically, there was no discernible difference in strobing between actual film and DVX/24p. Film strobes exactly as much as the DVX/XL2 in 24p.

On a negative film, single stop of over exposure does clip whites, but it enriches blacks and over saturates colors since you are in effect allowing more light to hit your film resulting in more saturated colors.
Click to expand...
Video isn't like negative film, it's like reversal film. You don't want to overexpose on video, just like you don't want to overexpose on reversal. To accomplish what you want, you'd rather want to lean towards underexposing. On reversal film, and on video, underexposing brings more saturated colors.
 
Mr. Barry Green

Mr. Barry Green

Boy, Barry. You sure got a handle on this stuff! Thanks for sharing.

Raoul
 
I might also add that that article also gives hints on camera adjustments to help reduce the strobey effect and bring it more in line with film, although the kinds of adjustments in question are only available on the full size cameras and require expensive charts and scope monitoring to get right.
 
Roberts was referring to the HD cams being used at the time (mid-2002), and he doesn't specify which ones. That was before the DVX. Barry's DVD demonstrates that the DVX's motion rendering, the strobiness, is *identical* to film's.
 
Jubal, Alan was referring to cameras such as the F900 using PsF, as well as the Varicam (which has been around for a number of years). What he says there also applies now. I've been in many conversations with him about the subject of filmlook recently. It matters not whether it's a DVX100 or a Varicam, as he points out even 24p is more strobey than real film due to the way video and film handle different frequencies. That's why he suggests these can be adjusted in the larger cameras (there are seperate detail frequency settings in those cameras for edge detail etc).
 
I don't doubt his veracity, or yours.

I also don't doubt the results of tests and demonstrations I have viewed with my own eyes, including my own, wherein the strobiness and motion rendering were identical.
 
I just shot a 20 minute short (almost done!) with a shutter speed of 1/36th of a second for most of the footage, because a ton of it was shot on a (relatively poorly used) glidecam. The rest was shot between 1/48th and 1/60th for syncho-scan. NOTHING strobes so far as I can tell. Nothing looks super-smooth like 60i, either, though.

One thing I did notice: I shot some footage at 30p with a 1/30th of a second shutter speed, and it looks MUCH smoother, but in a bad way. I had to convert some of this footage to 24p for the movie, and 80% of it looks okay because it's a telephone conversaion, but when a character moves, it's horrible. Even before conversion, the motion was incredibly different.

The "strobiness" people complain about and "film look" people herald as so great are really the same thing, just one in big doses and one in small doses. I don't do hand-held with the dvx as much as I might with another camera, but other than that 24p hasn't cramped my shooting style at all. Strobiness is much less of an issue than one would expect if you use the camera at all practically.
 
It all depends on how the camera is used, but also those frequencies. I'm alan for clarification on this, but the way I understand it it's the sharpness of video that makes the strobiness more apparent. It's not that video actually strobes more than film in 24p, but that the strobe is more noticable because of the way edge detail is handled. When the picture is less sharp (or edges are anti-aliased more) it means that the motion blur from the strobiness can 'blend' more from frame to frame. But as I say I'm trying to get a better clarification off Alan.

Policar, just off the point for a second, why did you use 1/30th shutter? When I first started using psf mode with my camera I assumed it was defaulting to a 1/50th shutter (I use PAL), and a friend and I were perplexed as to why there was so much motion blur. It looked dreamy. I later discovered that the camera needs the shutter switched on and forced into 1/50th mode to get the correct motion cadence. So I'm slightly confused as to why you used 1/30th instead of 1/48th for most of it? Was it for effect?
 
... ive never had a problem finding "strobe" / "jutter" /"jitter" / "flicker" in any 35mm feature ive watched on the big screen or on dvd. once you look for it , youll find it very easily . the issue is just that people dont know how to use a 24fps aquisition camera like the DVX correctly , and then when they sit there staring at the footage looking for the "film look" they notice the strobe. i challenge anyone of these untrained people to rent a 35mm camera, and shoot the same thing they shot with the dvx, and bring me back some perfectly smooth and motion jutter free footage. we can talk tech all day about how the digital process is different than te mechanical and chemial film process, but at the end of the day the results are indiscernable to the human eye or brain anyway. this whole "strobe" issue is an old dead horse. i hate to see it get dug up just to kick it again. the issue here is whether smoothing out 24p is a good thing. .. my personal answer is of course no. i think that they may have done that just because so many people in the video world do not understand 24p, and how to handle it. specifically in japan . they shoot almost everything 60i, and mostly dont understand why we want this "jittery" 24p. being that the camera is from a japanese manufacturer, it was probably their technicians under this line of thinking and in that sort of understanding that came up with the *sweet* idea to try and fix what didnt need fixing. granted japan makes most all video cameras, and the make plenty of true 24p cams as well. it could be some obscure technical obstruction that made them do it like this for the camera or HDV or whatever. at any rate. its nothing to get our undies bundled about. it might still look fine. like barry said well have to wait and see. i personally am not too google eyed over the JVC to begin with anyway because its mpg2, and tape based. i couldnt care less about the interchangeable lense. i can change the streering wheel on my car too, but dont hold your breath waiting for me to do it.

i think htat the HDX will have alot of the same P2 functionality as its big brother the SPX800. so if anyone wants a glipmse of what the HDX could have, just check out the SPX800 brochure and pay attention to what the P2 functionality has to offer.

this JVC camera looks like its going to be a very nice camera. should make alot of people very happy. true 24p or no true 24p.. at least its a step forward in the industry. well have to wait and see just how farthat step will take each one of us in our own personal journeys.
 
The strobing to me is a non issue. Films these days use a lot of handheld, so I don't believe people when they say that you shouldn't do this or that with film or progressive.

However I think people are completely misunderstanding me and beocming defensive for no reason at all. People here like 24p because they want to get as close to film as they possibly can. I'm trying to point out something that could help things to look even more like film and I'm trying to find out the knowledge from someone who has made filmlook on video his lifes work in recent years. I'm trying to help you guys!
 
Jubal28 said:
We know. You don't care about the film look. You've made that abundantly clear.

But we're not you.
Click to expand...

You can't mean that filmlook = strobiness. Strobiness is something a cameraman don't want to have. The magical look can't be the strobiness. The magical look is the color, dof and all those things making a film look like film but strobiness is a weakness.
 
well, ...strobiness isnt really a weakness, its an asthetic choice that creates a more surreal visual experience which allows the view to get into the story more.. at least thats one of the reasons why 24fps was kept as the motion picture standard frame rate over all these years. they could have changed it at any time once the technology was there. it had the same motion back then as it does now, ..and simply put, thats because they wanted to keep that motion. otherwise they could/would/should have started shooting everything at a higher framerate years ago in the name of progress.
 
No, 24fps was not kept as an aesthetic choice. Not really. There's the cost of the film for one thing. A roll of film wouldn't last as long and would have to be changed more often. The cameras and indeed the projectors would need to be running at double speed for higher framerates hence increasing the chance of something going wrong. Then there is the simple issue of light. Simply put higher framerates on film require much more light, and even with todays stocks it would mean increasing light output for the same effect in a given shot.

I think that when 50 and 60p become common in future HD cameras and even on DVD's with films that have been shot entirely on high end HD cameras at those frame rates, that feature films at 24p will start to look a little rickety by comparison, and may well follow suit.

I like 24p for one reason, and one reason only. People associate the cadence with high end productions. At the moment. This doesn't mean it will stay that way.

Higher framerates in cinemas would open up more possibilities for camerwork and camera movement and avoid some of the motion sickness problems of some current films.

I would be very interested in seeing a 60p HD shot movie on a big screen. Very interested indeed.
 
SergejIvanovits said:
You can't mean that filmlook = strobiness. Strobiness is something a cameraman don't want to have. The magical look can't be the strobiness. The magical look is the color, dof and all those things making a film look like film but strobiness is a weakness.
Click to expand...

I certainly mean that the strobiness is the result of motion rendering which is identical between the DVX and film, and that it's a big part of the film look.
 
Simon Wyndham said:
For those interested here is Alans response;
http://www.dvdoctor.net/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=8&t=003375#000002
Click to expand...

You misrepresented what I said. What I *said* was that paper was written before the DVX and applied to then-existing HD cameras. I didn't say Alan Roberts could not or would not reach the same conclusion re: the DVX; I only said that a paper written then, not taking into account developments SINCE then, is not necessarily informative of the discussion immediately at hand.
 
iamloser said:
...they could have changed it at any time once the technology was there. it had the same motion back then as it does now, ..and simply put, thats because they wanted to keep that motion. otherwise they could/would/should have started shooting everything at a higher framerate years ago in the name of progress.
Click to expand...

The new 48fps film projection is here but I guesss never going to be a new standard because it needs millions and millions to be invested all over the world. Why invest if what we have can make money?

Back to strobiness. Everyone sayes you have to tread your 24p camcorder like a 35mm filmcamera. Why? Because during all those years cameramans all over the world had to learn how to work around this weakness. They don't want strobiness and I guess noone of you wants to watch a strobi film in the cinema.
 
You must log in or register to reply here.
Back
Top