[macintologist]

How come we never see flicker on CRTS in movies and television shows?

For example:

Image:Lost0223 anomaly.png - Lostpedia
[removed oversize image --tooki]

Is it some sort of CG superimposition?

[Dakar]

If there's one thing I recall, its when you have documentary style or outside cameras on sets, they often show refreshing on those monitors, even though on the actual show/movie they don't

So my answer is, I don't know.

Edit: Yeah, that looks added to me.

[ghporter]

First, it would bother the viewer and interrupt the story use of the screen, so they don't let it happen. Second, it's possible to sync the film camera's frame rate with the montior's so that there IS NO FLICKER. That's pretty simple with today's digitally managed film cameras.

The picture you posted looks odd, like it is indeed superimposed. But I think that instead it's just turned up so bright that there's a lot of light spill on the bezel which makes it look kind of flat.

[macintologist]

Originally Posted by ghporter

First, it would bother the viewer and interrupt the story use of the screen, so they don't let it happen. Second, it's possible to sync the film camera's frame rate with the montior's so that there IS NO FLICKER. That's pretty simple with today's digitally managed film cameras.

The picture you posted looks odd, like it is indeed superimposed. But I think that instead it's just turned up so bright that there's a lot of light spill on the bezel which makes it look kind of flat.

So if I set the refresh rate on a monitor to 60hz wouldn't that sync up with the 60fps of ntsc cameras?

[ghporter]

Not that simple; the referesh rate has to be related to the camera's frame rate AND SYNCED WITH IT. It takes some fiddling, but there are techniques for doing this. I'd have to do some research to find the specific methodology.

[phantomdragonz]

Originally Posted by macintologist

So if I set the refresh rate on a monitor to 60hz wouldn't that sync up with the 60fps of ntsc cameras?

30fps BTW

Zach

[kmkkid]

A lot are superimposed. You can tell by the mishmash of Operating systems they use on the monitor screen. I always laugh when I see a windows taskbar with OS X windows, or the invert - Menubar with Windows windows.

[rickey939]

I still prefer seeing the Windows-looking folders, within OS X in most movies. Fun stuff!

[macintologist]

Originally Posted by phantomdragonz

30fps BTW

Zach

Actually it's 60fps

Look at NTSC television, then look at a simple screensaver locked down at 30fps, its not smooth at all. Then jack it up to 60fps and it looks smooth just like TV does.

[TETENAL]

Originally Posted by macintologist

Actually it's 60fps

I think it's actually 60 half pictures per seconds which makes 30 pictures per second.

[CRASH HARDDRIVE]

Most movies and TV shows are shot on film at 24fps. The image you see on a TV has been converted to 30fps using a pulldown. (And yes, video is 60 fields per second/ 30 frames)

The simplest way I know of to film a monitor is to use a sync box on the monitor that allows precise adjustment to match the camera's shutter speed. More seat of the pants is to adjust the shutter speed to match the monitor.

Many times multi monitors are run off the same sync box, and the source is pre-recorded.

[Railroader]

Originally Posted by macintologist

Actually it's 60fps

Look at NTSC television, then look at a simple screensaver locked down at 30fps, its not smooth at all. Then jack it up to 60fps and it looks smooth just like TV does.

ACTUALLY, it's 29.97 interlaced frames per second or 59.94 hertz (nominally 60 Hz/1.001) refresh frequency.

http://en.wikipedia.org/wiki/NTSC#Li...d_refresh_rate

[macintologist]

Originally Posted by Railroader

ACTUALLY, it's 29.97 interlaced frames per second or 59.94 hertz (nominally 60 Hz/1.001) refresh frequency.

http://en.wikipedia.org/wiki/NTSC#Li...d_refresh_rate

Still but what you're seeing looks like 60fps

[ghporter]

The 60 fields per second was chosen for the same reason we use 60Hz power in North America: it's the closest we can get to the human eye/brain frame rate. 50Hz, used in Europe, is often bothersome to people because it's just a little too slow for them, and EVERYTHING flickers.

Anyway, there's a rather complex conversion between 24 film frames and 30 video frames (of two fields each) that winds up giving you PERFECT sync. There are devices used to sync the sound, film camera and an entire video system on set (which are not cheap, either) to give the perfect impression of perfect sync. And then they came out with plasma and LCD displays-this requires a different sync strategy, not because of frequencies, which are much more flexible on computer monitors, but because of the WAY digital computer monitors like plasma and LCDs refresh-it's not a "flyback" system like on a CRT. Suffice to say it's less complex, but more involved because the video cards driving everything have to be perfectly synced with each other as well as the film camera system.

[Railroader]

Originally Posted by macintologist

Still but what you're seeing looks like 60fps

I guess you're not an engineer.

[voodoo]

Originally Posted by ghporter

The 60 fields per second was chosen for the same reason we use 60Hz power in North America: it's the closest we can get to the human eye/brain frame rate. 50Hz, used in Europe, is often bothersome to people because it's just a little too slow for them, and EVERYTHING flickers.

60 fields = 30 frames.

The eye sees smooth motion at a little over 20 fps. Movies are at 24 fps, PAL at 25 fps and NTSC at 30 fps.

V

[macintologist]

30 frames yes but as previously noted it looks like 60fps.

[Gamoe]

As I recall (somewhat incompletely) the original Macintosh was known to be very sync-friendly for film cameras back in the day.

[voodoo]

Originally Posted by macintologist

30 frames yes but as previously noted it looks like 60fps.

60 fields per second that look more or less like 30 fps. A field is half a frame.

Hence possible flickering.

Look, have you ever been to the movies? Of course you have. There the film is shown at 24 fps in full frames. There is no flickering and the motion is smooth.

24 fps is more than enough.

V

[starman]

I've noticed in end credits, things like "24 FPS monitors supported by...." so they know what they're doing.

[Railroader]

Originally Posted by macintologist

30 frames yes but as previously noted it looks like 60fps.

You're not quite wrapping your head around it are you?

It's refreshed roughly 60 times per second, but only every other line. Add them together and you'll only get 30 frames per second.

It's very simple.

[OwlBoy]

The monitor in the picture above is obviously has the screen digitally placed there. (many things about the image show this)

-Owl

[macintologist]

Originally Posted by Railroader

You're not quite wrapping your head around it are you?

It's refreshed roughly 60 times per second, but only every other line. Add them together and you'll only get 30 frames per second.

It's very simple.

I know that but take a look at something running 30fps on your Mac. It's smooth but not the smoothest. Now look at something that is 60fps on your Mac. That's how smooth TV appears. It's all about perception.

[tooki]

OK, let's examine a few issues:

1. the flicker when filming a CRT (which is technically "temporal aliasing", for those who care) occurs when there's a fairly large mismatch between the refresh rate of the CRT and the frame rate of the camera.

2. "crawl" when filming a CRT is caused by a very small mismatch.

3. movies, and many TV shows, are and were filmed at 24 frames per second. "3:2 pulldown" is used to play it back on NTSC systems, while 24fps footage is simply sped up by 4% and played back at 25Hz for PAL and SECAM systems.

4. movies don't flicker in the cinema because each frame is shown twice, yielding a frame rate of 24fps and a refresh rate of 48Hz.

5. NTSC black and white TV is 30fps with a 60Hz (interlaced) refresh rate. NTSC color is 29.97fps with a refresh rate of 59.94Hz (interlaced). The missing fraction of a frame is used to insert color information.



Filming CRTs is done one of two ways: in one, the image is superimposed later. In such a case, the CRT could be off, or it could be flickering. Either way, it wouldn't matter. The sample above looks like a superimposed image.

The other way is to use modified TVs and video sources that run at exactly 24fps (with a compatible refresh rate), electronically synchronized to the camera shutter (similar to genlock in video). If you look in the credits of many movies, there's a person listed with the title "24fps playback". They coordinate this specially synced video. This method allows CRTs to be filmed with zero flicker.

tooki

[tooki]

Originally Posted by macintologist

I know that but take a look at something running 30fps on your Mac. It's smooth but not the smoothest. Now look at something that is 60fps on your Mac. That's how smooth TV appears. It's all about perception.

It's so much more complicated than that.

The shutter speed used when filming makes a HUGE difference in the perceived smoothness. So does the difference between interlaced and progressive footage. That's why 24fps (progressive) film appears smoother than 30fps video (from an interlaced source) on a computer.

There are also questions of decode lag, display lag, audio sync, etc on a computer. A TV usually doesn't have any of those issues to deal with.

tooki

[brassplayersrock²]

YEAH! you tell 'em tooki!

in all seriousness:
this thread has taught me a lot more then I ever thought I would about frame rates. thanks you guys

[Railroader]

Originally Posted by macintologist

I know that but take a look at something running 30fps on your Mac. It's smooth but not the smoothest. Now look at something that is 60fps on your Mac. That's how smooth TV appears. It's all about perception.

Yup, I was right.

You're not getting it.

[ghporter]

The 60 field refresh rate makes the image LOOK a little more "live" than it would with a simple 30fps rate. That's one of the reasons interlacing is used in the first place. But there are still only 30 frames; each interlace refresh (first the odd lines, then the even lines, then back to the odd...) is only HALF of a frame, so 60 fields is really 60 HALF-FRAMES per second. The extra motion caused by the interlaced lines refreshing looks a bit better (and brighter) than it would without, but it's still just 30 FRAMES.

[Gamoe]

However, I do tend to see flickering in the movie theatre, but very particularly in scenes where there is a lot of white or approximately white.