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2K better than 4K !


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#1 alan mourgues

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Posted 13 January 2009 - 12:07 PM

Hi there
I´m just testing my new RED ONE camera. I found straight away a noticebale strobing effect, alot worse than in other 24p cameras

With shutter control you can reduce the exposure time to avoid motion blur, but you get flicker anyway. If you have fast movment within the frame (either the camera or the object moves), the only thing you can do to avoid flicker is to increase the frame rate (besides reducing dof so focusing on the object only). Isn´t that a reason good enough to prefer 2K rather than 4K in takes with fast movment ? (2k allows higher frame rate, so you can record at, say 100 fps and then speed it up in post). I´m wondering

I haven´t quite gone through the post workflows yet, and I was wondering how to handle different takes recorded at different resolutions and different frame rates in post.

Let´s say that I´m recording at 4K 2:1 @ 24fps, but I have some takes in between where I decided to shoot at 2K 2:1 so to get 100 fps and therefore avoiding too much flickering. I´ll need to overcrank the 100 fps take to get it to the normal speed within the project. Is it achiveable such a workflow ? Any reccommendations ?...any particular post software better than the other in this matter ?
Thanks a lot
Alan
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#2 Peter Milanov

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Posted 13 January 2009 - 01:12 PM

My first impression after reading your post: eh...what? :unsure:


I have not found RED fotage to have more noticable strobe than other 24p cameras. It´s all about the shutterangle/time. If you are at 180 degrees you have about the same strobe effect as shooting on film. On digital you can go 360 degrees for a smoother look, but you will also get a look more associated with video. If you shoot at 100 fps and then speed it up in post it will be about the same thing as shooting at 45 degrees (or a shutterspeed at about 1/200 sek) (hope I got the math right, I am a little tired today)

To get a smoother look when shooting at 100fps you also need to playback at that speed.
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#3 Scott Fritzshall

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Posted 13 January 2009 - 02:15 PM

I'm also not exactly sure what you're talking about. You either have motion blur, or you have strobing. If you shoot at a higher frame rate with intent to retime it back to normal in post, you're either going to just take whole frames (for instance, shooting at 96fps and using every 4th frame), in which case you've got the exact same strobing as if you had shot 24fps with a 45deg shutter, or you do some sort of frame blending, which can be much more difficult than you would expect, and the goal of that is to get it to look like it had been shot normally to begin with... I don't quite get what problem you're having or why you're going so far out of your way for it. It's probably not a good idea to mix 4k and 2k RED footage, as there is a pretty significant difference in sharpness, and it will probably intercut poorly.
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#4 John Sprung

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Posted 13 January 2009 - 03:32 PM

It seems that what's missing here is an understanding of the fundamentals. Motion blur isn't a bad thing, it's a necessity. Without motion blur, there are no motion pictures. Instead, what you get is an overly fast slide show.

Skipping (mistakenly called strobing) has been well known for about a hundred years. Until recently, it has been unavoidable except by avoiding things that move too fast. Now we can shoot at very nearly a 360 degree shutter, and get enough motion blur to accurately reproduce any moving object. Have a look at the circular dolly shot in "What Love Is" -- where Cuba Gooding Jr. gets the bad news. He stays sharp, the BG swirls into a blur, but all without skipping. That was impossible to do before digital cameras. (DP: Dave Stump, ASC)

You may want to shoot a small shutter angle once in a while as a gimmick, but for normal work, 180 degrees or more.....




-- J.S.
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#5 Joe Taylor

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Posted 13 January 2009 - 04:38 PM

I´m just testing my new RED ONE camera. I found straight away a noticebale strobing effect, alot worse than in other 24p cameras.



Not sure how long you have had your camera, but it almost sounds like you are basing your viewing experience by watching your QT Proxies. Have you had time to render and work with you footage?
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#6 Sing Howe Yam

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Posted 13 January 2009 - 07:12 PM

I've just finished shooting a feature on the camera and I didn't get an of the problems you've listed. As Joe said it might be your playback that is causing this, I shot the whole film at 4K @ 2:1 @ 24fps and had no problems and did some fast dolly shots. Shot some at 2k for slow motion and the footy cut together really well. Then again t depends what you're projection is going to be, the 2k I would be more worried about my lenses getting longer, which can be a bummer at times.
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#7 Zakaree Sandberg

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Posted 14 January 2009 - 04:45 AM

what everyone else said. Check your computer (make sure it can handle the footage).
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#8 alan mourgues

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Posted 14 January 2009 - 09:20 AM

thanks guys for your comments
The issue I´m pointing out is simple. Recording 24p generates strobing / juddering. With the RED ONE, the results seem to be a lot worse than in other 24p cameras. This issue has been highly addresses in many forums all over the net. So, when you have fast movement within the frame, the only way to reduce judder is increasing the frame rate. So, I was wondering; I have one take at 4K 24pfs, then, for the next take, I wanna record it at 96 fps, but I need to go down to 2K to achieve this. Then overcrank 400% this take and finally build my 2-takes project at 24fps. Is there any problem for this in post ? That was my original question

Then form your comment, I realize I´m missing the shutter angle concept. Can anybody tell me in straight english what is this ?...the camera allows you to set the shutter speed and a variable named phase, nothing else. What is this shutter angle stuff ?..any explanation o good link wold be much appreciated
Thanks again
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#9 Filip Orlandic

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Posted 14 January 2009 - 11:56 AM

RED = FILM stobing effect :P

Don't worry :P
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#10 John Sprung

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Posted 14 January 2009 - 04:33 PM

> The issue I´m pointing out is simple. Recording 24p generates strobing / juddering.

Not necessarily. It depends on your shutter angle and how fast things are moving in frame. The correct name for it is "skipping".

> With the RED ONE, the results seem to be a lot worse than in other 24p cameras.

Using the same frame rate and shutter angle, all cameras should give you the same amount of skipping. Latency in feeding your display could be the problem.

> So, when you have fast movement within the frame, the only way to reduce judder is increasing the frame rate.

No, shutter angle and/or frame rate. The problem with increasing the frame rate is that you then have to display it at that rate. That was what ShowScan was all about, shooting and projecting at 60 FPS.

> So, I was wondering; I have one take at 4K 24pfs, then, for the next take, I wanna record it at 96 fps, but I need to go down to 2K to achieve this. Then overcrank 400% this take and finally build my 2-takes project at 24fps. Is there any problem for this in post ?

From the context above, I wonder what is your understanding of the term "overcrank"? To most of us, it merely means shooting at a higher frame rate than the display frame rate, which results in a slow motion effect.

> Then form your comment, I realize I´m missing the shutter angle concept. Can anybody tell me in straight english what is this ?...

Ah, this is the crux of the problem. Motion pictures were first made by mechanical cameras, and for most of their history, such cameras were the only way to make motion pictures. So, the mechanical way of looking at it is how we quantify the relationship between frame rate and exposure time. The shutter in a film camera is usually a spinning disc, part of which is cut away to let light reach the film, the rest of which protects the film during the mechanical pulldown. Often it's a two blade disc for balance and vibration reasons, but the specification is always given in terms of a single blade shutter. The shutter angle is just the angle of the open part. One divided by the frame rate in frames per second gives you the time in fractions of a second represented by each frame. Multiply that by the shutter angle and divide by 360 degrees to get the exposure time per frame.

Using shutter angles rather than actual exposure times is sort of handy in that it helps avoid the mistake of specifying an exposure time longer than the frame period, which is physically impossible. It's also handy for sampling theory purposes, because it tells us how far undersampled we are. It would have been even easier if they had used percentages, like the electronics guys do with duty cycles, but for historic reasons, it's angles.

So how does this all work in the real world? Suppose we have a wide locked off shot, and somebody throws a ball across the frame fast enough that it goes twelve times its diameter per frame. If we're shooting with a 180 degree shutter, the shutter opens and we capture the ball as it advances six diameters. Then the shutter is closed while it continues six more diameters, and it all happens over again. The ball appears on screen as streaks one ball diameter high by six ball diameters long, and the streaks from frame to frame are six diameters apart. That's skipping.

Suppose we go to a much smaller shutter angle, say 15 degrees. Now the ball only moves half its diameter during each exposure, so it's a slightly elongated blob instead of a streak. But the blobs are now 11.5 ball diameters apart. The skipping is much worse.

Next think what happens if we go to the largest shutter angle we can actually make electronically, say 359.5 degrees. Now the ball appears as continuous streaks, the half degree worth of gap is too small to notice. There's no detectable amount of skipping.

Because it takes time to physically move the film, film cameras typically don't do much better than 180 degrees as a maximum shutter angle. There were special kinescope movements that could do 288 degrees, but for general production use, 180 was about it. This means that we could capture at most about half of the motion information, which is quite severe undersampling. The rest of the motion information from the real world is lost, like the gaps between the ball images above. Undersampling causes artifacts, and this kind of temporal undersampling is why the wagon wheels sometimes go backwards in old westerns.




-- J.S.
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#11 David Mullen ASC

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Posted 14 January 2009 - 04:34 PM

thanks guys for your comments
The issue I´m pointing out is simple. Recording 24p generates strobing / juddering. With the RED ONE, the results seem to be a lot worse than in other 24p cameras. This issue has been highly addresses in many forums all over the net. So, when you have fast movement within the frame, the only way to reduce judder is increasing the frame rate. So, I was wondering; I have one take at 4K 24pfs, then, for the next take, I wanna record it at 96 fps, but I need to go down to 2K to achieve this. Then overcrank 400% this take and finally build my 2-takes project at 24fps. Is there any problem for this in post ? That was my original question

Then form your comment, I realize I´m missing the shutter angle concept. Can anybody tell me in straight english what is this ?...the camera allows you to set the shutter speed and a variable named phase, nothing else. What is this shutter angle stuff ?..any explanation o good link wold be much appreciated
Thanks again


If you want a 24 fps look, shoot at 24 fps. Don't try and get too clever. What could look more like motion sampled 24 times a second than sampling motion 24 times a second?

If you match the shutter angle of a film camera, usually 180 degrees (i.e. half closed / closed 50% of the time) which means a shutter time of 1/48th at 24 fps, then you should get fairly close to the same look on the RED camera. A digital electronic shutter will never be 100% like a spinning mechanical shutter, but it's close enough.

The strobing is just endemic to 24 fps photography -- it's a fairly low number of samples over time to capture motion smoothly. 24 fps film has the same strobing issues.

If you are seeing something bizarre or unusual, then it's probably not due to shooting the RED at 24P with a 1/48th shutter, it's something wrong in how it's been posted or how it is being viewed.

A film camera shutter is a spinning circular disk rotating in front of the aperture with a pie slice opening to expose the film. A 180 degree shutter is a half-circle.
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#12 Chris Gloag

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Posted 15 January 2009 - 10:06 AM

If you want a 24 fps look, shoot at 24 fps. Don't try and get too clever. What could look more like motion sampled 24 times a second than sampling motion 24 times a second?

If you match the shutter angle of a film camera, usually 180 degrees (i.e. half closed / closed 50% of the time) which means a shutter time of 1/48th at 24 fps, then you should get fairly close to the same look on the RED camera. A digital electronic shutter will never be 100% like a spinning mechanical shutter, but it's close enough.

The strobing is just endemic to 24 fps photography -- it's a fairly low number of samples over time to capture motion smoothly. 24 fps film has the same strobing issues.

If you are seeing something bizarre or unusual, then it's probably not due to shooting the RED at 24P with a 1/48th shutter, it's something wrong in how it's been posted or how it is being viewed.

A film camera shutter is a spinning circular disk rotating in front of the aperture with a pie slice opening to expose the film. A 180 degree shutter is a half-circle.

What do you think about a 30p cinematography? Canon 5D MK2, for example? Converting later to 24 fps.
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#13 John Sprung

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Posted 15 January 2009 - 01:51 PM

What do you think about a 30p cinematography? Canon 5D MK2, for example? Converting later to 24 fps.

The big problem is how do you fake the missing information? If you want 24, the best thing to do is shoot 24.



-- J.S.
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#14 Chris Gloag

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Posted 16 January 2009 - 02:02 AM

The big problem is how do you fake the missing information? If you want 24, the best thing to do is shoot 24.



-- J.S.


I have found these methods.

http://cinema5d.com/...p...=a&start=10

http://cinema5d.com/....php?f=13&t=389

http://cinema5d.com/...c.php?f=13&t=73

http://www.dvinfo.ne...-you-judge.html

Thoughts?
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#15 Will Earl

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Posted 16 January 2009 - 06:56 AM

Retiming 30p to 24p wouldn't present to much of a problem in itself - although I haven't ever needed to retime 30p to 24/25p. You may occasionally get the odd artifact and a slight loss in resolution.

It'd also be a headache retiming an entire long form project.
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#16 alan mourgues

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Posted 16 January 2009 - 08:17 AM

Ok. Thanks a ot for your replies
Practical questions:

1) Shooting 24p, having movement from medium to fast within the frame. Do you prefer 1/24th or 1/48 ?. The first gives more bluring within each frame but no skipping, and the second reduces motion but adds skipping. Anything in between maybe (1/32th) ?

2) Why while shooting with RED, my HD monitor shows so much flicker ?....The proxys shown on the QT player in my MAC show the same flickering images, but after rendering, exporting, the fickering is reduced a lot when viewing the exported .mov with the same QTPlayer in the same MAC. My monitor is a PANASONIC BT-LH1700WP, and my MAC is a MAC Book Pro 17", 2.5 GHz Intel Core duo, HD 320 GB Serial ATA @7200rpm, Super Drive 8X DL, memory 4GB, SDRAM 2x2GB

3) For a TV commercial, is it preferable to shoot 30p (TV display rate) or 24p ?...this first reduces skipping but is more videoish, and the second gives the "film-look" but more skipping.

4) This so called film-look of 24p, isn´t it lost when taking it to 30 fps for tv transmission ?....Wher in the pipleines is this conversion done anyway ?...Do I have to make it myself in post and export a 30fps movie ? Or I just finish at 24p and forget about it ? (For tv commercial)
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#17 Matthew Rogers

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Posted 16 January 2009 - 09:46 AM

1) Shooting 24p, having movement from medium to fast within the frame. Do you prefer 1/24th or 1/48 ?. The first gives more bluring within each frame but no skipping, and the second reduces motion but adds skipping. Anything in between maybe (1/32th) ?


1/48 is what you normally shoot at when shooting 24fps. 1/24 gives to much motion blur. Anything above 1/48 is probably going to look too "suttery".

2) Why while shooting with RED, my HD monitor shows so much flicker ?....The proxys shown on the QT player in my MAC show the same flickering images, but after rendering, exporting, the fickering is reduced a lot when viewing the exported .mov with the same QTPlayer in the same MAC. My monitor is a PANASONIC BT-LH1700WP, and my MAC is a MAC Book Pro 17", 2.5 GHz Intel Core duo, HD 320 GB Serial ATA @7200rpm, Super Drive 8X DL, memory 4GB, SDRAM 2x2GB


Are you seeing flicker, or does the image have a stutter? There is a big difference there. You can get flicker in lights like Kinos and HMI's, but at 24fps, you shouldn't have an issue with most lights. Are are you seeing a stutter when compared to 60i video footage?

3) For a TV commercial, is it preferable to shoot 30p (TV display rate) or 24p ?...this first reduces skipping but is more videoish, and the second gives the "film-look" but more skipping.


It depends on the look you are going for. High end spots are normally shot on film at 24fps. Lower end spots are normally shot 60i (30fps). I don't know why you are having issues with stuttering. I've never had an issue with the RED, or any other 24p camera, when shooting 24p. Of course, if you've only ever shot 60i, then 24p might look weird, and you might not like it. Personally, I love it. Doesn't look like reality.

4) This so called film-look of 24p, isn´t it lost when taking it to 30 fps for tv transmission ?....Wher in the pipleines is this conversion done anyway ?...Do I have to make it myself in post and export a 30fps movie ? Or I just finish at 24p and forget about it ? (For tv commercial)


You would think so, but when you telecine it up to 29.97 (60i) you are not creating frames with new information. You are actually smartly duplicating certain frames. Personally, I normally edit the entire spot in 24p and when I'm done telecine it up to 29.97.

Matthew
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#18 Chris Durham

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Posted 16 January 2009 - 01:38 PM

Are these rolling shutter artifacts he's talking about? He mentioned them occurring with any kind of fast action in frame.

If it is, then the trick is to get the shutter speed correct. A rolling shutter artifact on CMOS is caused by the scanning of the chip. It scans the same way a tv paints lines on a screen, so if you capture a new frame and the scan is off-sync you get an image that is half one frame and half the next. (At least this is my understanding - having only seen samples and not dealt with the issue myself).

As I understand it, you can mitigate the effect by increasing your shutter speed while leaving your frame rate alone. Just remember that if you change your shutter speed to 100fps (approx. 45 degree shutter angle) you lose a stop of light so you have to compensate.
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#19 John Sprung

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Posted 16 January 2009 - 02:17 PM

Thoughts?

It's amazing how much talking is done by people who don't quite know what they're talking about. ;-)




-- J.S.
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#20 John Sprung

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Posted 16 January 2009 - 02:40 PM

> 1) Shooting 24p, having movement from medium to fast within the frame. Do you prefer 1/24th or 1/48 ?. The first gives more bluring within each frame but no skipping, and the second reduces motion but adds skipping. Anything in between maybe (1/32th) ?

It's entirely a matter of taste -- do you prefer chocolate or vanilla ice cream? Historically, the region between 180 and 360 degrees (1/48th to 1/24th) hasn't been available in film, so it doesn't have the "film" look. Because the images in video are actually fields, not frames, and we see either 50 or 60 of them per second depending on where we are, and the scanning of TV is in effect a rolling shutter with a 92% duty cycle, stuff shot at or near 360 degrees tends to have more of a video look.

> 2) Why while shooting with RED, my HD monitor shows so much flicker ?....The proxys shown on the QT player in my MAC show the same flickering images, but after rendering, exporting, the fickering is reduced a lot when viewing the exported .mov with the same QTPlayer in the same MAC. My monitor is a PANASONIC BT-LH1700WP, and my MAC is a MAC Book Pro 17", 2.5 GHz Intel Core duo, HD 320 GB Serial ATA @7200rpm, Super Drive 8X DL, memory 4GB, SDRAM 2x2GB

It sounds like buffering and pipeline issues between the camera and the display. The best idea is just to ignore it, since you know that the material renders out nicely, and treat the on-set monitor as you would the crappy flickering video tap on a film camera.

> 3) For a TV commercial, is it preferable to shoot 30p (TV display rate) or 24p ?...this first reduces skipping but is more videoish, and the second gives the "film-look" but more skipping.

Again a matter of taste. On a commercial, it's the client's taste that matters, so the best thing is to ask them which look they prefer.

> 4) This so called film-look of 24p, isn´t it lost when taking it to 30 fps for tv transmission ?....Wher in the pipleines is this conversion done anyway ?...Do I have to make it myself in post and export a 30fps movie ? Or I just finish at 24p and forget about it ? (For tv commercial)

Not only isn't it lost, it gets an extra "look" added on top of it. Perceptually, TV isn't 30 frames, it's 60 fields. Film gets transferred (telecine) using 3-2 pulldown. What that means is that the first flim frame is transferred to two video fields, the second to three video fields, the third to two fields, the fourth to three fields, and so on for the duration of the show. The motion sampling from the real world is still the same 24 frames per second, but now you see them with a little extra time given to every other image. People who live in the NTSC countries are used to seeing this artifact, and don't notice it. When people from the PAL/SECAM parts of the world visit here, they're very much aware of the 12 Hz vibration that gets added to anything that moves on a film originated TV show.

(OTOH, when we visit over there, we're aware of the 50 Hz flicker of the entire picture, which they're accustomed to seeing.)



-- J.S.
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