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Author Topic: Canon 5D MkII: almost there  (Read 46750 times)
Ray
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« Reply #20 on: September 20, 2008, 11:17:50 PM »
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For anyone who is still confused about the significance of 24p, I'll offer my opinion which can be read by those who have not put me on their 'ignore' list.

For digital videocams and general video recording devices, the significance is in the 'P', not the 24, except in so far as the 24p standard may lend itself to the in-built algorithms of certain displays which incorporate convoluted methods of converting the traditional film movie standard of 24fps into the electronic display standard of 60Hz, in the case of NTSC.

Converting 24fps movies into PAL has always been easier than for NTSC. One simply speeds up the movie almost imperceptibly to 25fps, then one doubles the frame rate to 50Hz, and Viola!

The downside with PAL is that sound can also be speeded up (without software to counteract that) so that those who have a sense of absolute pitch feel a bit uncomfortable. But I guess most people wouldn't notice the slightly higher pitch.

Generally, 30p is better than 24p, just as 50p would be better than 30p and 60p would be even better. P for progressive is generally better than i for interlaced.

The interesting thing about the video from the 5D2 is that each of the 30 frames per second is comprised of 1920x1080 fairly large pixels of 6.4 microns. If one were to construct a sensor that could hold 1920x1080 6.4 micron photosites, it would have to be around 12.3mm x 6.9mm in dimension. That's much larger than most (and probably all) consumer grade videocams. Small P&S digicams with video capability have a sensor size of around 5.4mmx4mm. More professional videocams have a sensor size of around 8.8mmx6.6mm (2/3" format).

The 5D2, seems to be very competitve regarding video quality, especially considering the low noise circuitry built into Canon sensors. P&S digicams and consumer grade videocams do not, I believe, have specialised pre-amplifiers at each photosite. Correct me if I'm wrong.

This camera is going to be difficult to resist for a spiritual person such as myself   .
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Jonathan Wienke
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« Reply #21 on: September 21, 2008, 06:28:30 AM »
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But not necessarily in a high quality manner, Jonathan. Video enthusiast have and do spend thousands of dollars on additional equipment to take care of conversion that is seamless and natural, and if they no longer do this, they are still very aware of these conversion issues when selecting a display or projector.

You've completely missed the point. Display designs have long since progressed past the point where their refresh rate is tied to the AC power frequency. When the display can natively offer a variety of vertical refresh rates, there is no frame rate conversion involved. I have a HDTV that can display 1080p at either 24 or 30 frames per second. It does so by altering the vertical scan rate of the LCD. There is no 3:2 telecine or frame doubling or any other frame rate conversion going on, it simply changes the frequency of the clock that drives the LCD refresh circuit so that the frame rate of the display matches that of the source video. As a result, there are no interlacing artifacts, and pans are smooth when viewing both 24p and 30p video.
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Ray
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« Reply #22 on: September 21, 2008, 08:06:24 AM »
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You've completely missed the point. Display designs have long since progressed past the point where their refresh rate is tied to the AC power frequency. When the display can natively offer a variety of vertical refresh rates, there is no frame rate conversion involved. I have a HDTV that can display 1080p at either 24 or 30 frames per second. It does so by altering the vertical scan rate of the LCD. There is no 3:2 telecine or frame doubling or any other frame rate conversion going on, it simply changes the frequency of the clock that drives the LCD refresh circuit so that the frame rate of the display matches that of the source video. As a result, there are no interlacing artifacts, and pans are smooth when viewing both 24p and 30p video.
[a href=\"index.php?act=findpost&pid=223004\"][{POST_SNAPBACK}][/a]


I don't believe I've missed the point. It has always been possible with modern technology to convert different systems to different refresh rates with greater or lesser success depending on the sophistication of the equipment. Of course, in this modern age, refresh rates are not tied to the AC power frequency, although that was built into the NTSC and PAL TV systems when they were first developed.

The point I'm making is that 24p is unwatchable as 24p. It's stuttery just like very old movies projected on old equipment. It has to be upgraded (converted) to a higher refresh rate, say 60Hz as a minimum. However, high end LCD TV displays now boast refresh rates of 100Hz which is what my 10 year old, standard definition CRT PAL TV also uses.

If it's necessary to convert the frame rate of video footage to a higher frame rate for the sake of smooth motion, then its better to start off with 30p rather than 24p.

If I've got that wrong, please be specific.
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Jonathan Wienke
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« Reply #23 on: September 21, 2008, 08:54:37 AM »
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The point I'm making is that 24p is unwatchable as 24p. It's stuttery just like very old movies projected on old equipment. It has to be upgraded (converted) to a higher refresh rate, say 60Hz as a minimum. However, high end LCD TV displays now boast refresh rates of 100Hz which is what my 10 year old, standard definition CRT PAL TV also uses.

24p is not stuttery when played back on a display that actually plays at 24p. It's only stuttery when played back on a display that is refreshing at a rate not evenly divisible by 24 and some frames are displayed for a longer period of time than others. If each frame is not displayed for the same length of time, the video will be stuttery regardless of whether it is 24p or 30p.
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Eric Myrvaagnes
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« Reply #24 on: September 21, 2008, 09:05:17 AM »
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One simply speeds up the movie almost imperceptibly to 25fps, then one doubles the frame rate to 50Hz, and Viola!

...

This camera is going to be difficult to resist for a spiritual person such as myself   .
[a href=\"index.php?act=findpost&pid=222973\"][{POST_SNAPBACK}][/a]
Ray, I'm going to have to take issue with your major point here. Even for a spiritual person, it takes more than than to create a Viola, as Stradivari, Amati, et al could tell you.

Or, perhaps you meant "Voila?"  
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Ray
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« Reply #25 on: September 21, 2008, 10:44:14 AM »
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24p is not stuttery when played back on a display that actually plays at 24p. [a href=\"index.php?act=findpost&pid=223023\"][{POST_SNAPBACK}][/a]

Johnathan,
I've never seen a display with a 24Hz refresh rate. You know enough about monitors to realize that LCDs have a minimum refresh rate of 60 Hz and that a flicker-free CRT, such as the Sony Multiscan G400 that I'm using as I write this, needs a minimum refresh rate of 70Hz otherwise it's a strain on the eyes. What's the matter with you?

Perhaps you misunderstand what 24p means. It refers to a display rate of 24 frames per second in a progressive mode as opposed to an interlaced mode.
When you watch a 24p movie on a display that can handle 24p material, each of the 24 frames is multiplied a few times to fit in with the refresh rate of the display.

A standard movie projector in the cinema will display each frame 3x in order to smooth out the stuttery effect. 30fps is less stuttery than 24fps and 60fps is less stuttery than 48fps.
« Last Edit: September 21, 2008, 10:46:16 AM by Ray » Logged
Ray
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« Reply #26 on: September 21, 2008, 10:52:39 AM »
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Ray, I'm going to have to take issue with your major point here. Even for a spiritual person, it takes more than than to create a Viola, as Stradivari, Amati, et al could tell you.

Or, perhaps you meant "Voila?"   
[a href=\"index.php?act=findpost&pid=223025\"][{POST_SNAPBACK}][/a]

That's a perfectly logical train of thought, Eric. Frames per second, Hz, sound frequency, hi fi, music, viola.  
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The View
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« Reply #27 on: September 21, 2008, 12:34:51 PM »
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Announcement of a Vincent Laforet movie shot with the 5dII.

http://www.dpreview.com/news/0809/08092101...eteos5dmkii.asp
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Jonathan Wienke
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« Reply #28 on: September 21, 2008, 03:50:30 PM »
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Johnathan,
I've never seen a display with a 24Hz refresh rate. You know enough about monitors to realize that LCDs have a minimum refresh rate of 60 Hz and that a flicker-free CRT, such as the Sony Multiscan G400 that I'm using as I write this, needs a minimum refresh rate of 70Hz otherwise it's a strain on the eyes. What's the matter with you?

Right back at you. A CRT has to have a high refresh rate because the phosphors in the tube emit a very short burst of light as the electron beam strikes them, and then quickly fade back to black. Any given pixel on the screen is lit less much less than 100% of the time. If you use a fast shutter speed to photograph a CRT screen (1/120 or faster) you will see a horizontal black band on the screen that follows in the wake of the beam--at any given instant, a large portion of the screen is completely dark. As a result, a CRT monitor requires a high vertical scan rate (>60 Hz) for our eyes to blend the flashing pixels into a smooth continuous image.

In contrast, one of the engineering challenges of designing LCD displays has been to make a pixel that can react fast enough to meaningfully display higher frame rates. Unlike a CRT, an LCD pixel does not fade to black between scans--it continuously displays a color until the next frame arrives, and then it fades fairly smoothly from the old color value to the new one. How long this process takes is defined by the response time of the LCD. The response time of the LCD also limits the maximum frame rate the LCD can display. A high-speed photograph of an LCD display will not show any black band in the image the way a CRT will. Each pixel is illuminated 100% of the time.

A true 24p HDTV may overscan at some multiple of 24 Hz (probably 120 Hz, since that divides evenly into both 24 and 30 Hz) to reduce the transition time from one frame to the next, but that has nothing to do with the high refresh rate needed by a CRT. While a CRT scanning at 120 Hz is flashing each 24p frame 5 times, a 24p LCD simply displays each frame for approximately 1/24th of a second. The LCD is not "flashing each frame multiple times" even if its internal scan rate is a multiple of 24 Hz. Each displayed frame smoothly fades to the next frame over a time interval determined by the response time of the LCD and its internal scan rate.

Here's an experiment for you to try:
Go to an electronics store that has a variety of plasma, CRT, and LCD displays--monitors, TV's, and HDTVs. Bring a DSLR with a fast lens. With the shutter speed at 1/1000 or faster, max ISO, and the lens wide open, photograph as many different displays as you can. Have the camera in portrait orientation so that the shutter curtains are traveling 90 degrees to refresh of the screen image. Make a note of which displays exhibit banding in the captured images, and see if there is any correlation to the perception of smoothness or flicker in the displayed video. Post your results.
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jjj
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« Reply #29 on: September 21, 2008, 06:02:58 PM »
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Here are some useful links that may explain some of the problems with the new technnology
http://dvxuser.com/jason/CMOS-CCD/   - rolling shutters - why thery are bad.
Video to demostrate the effects - http://www.ssontech.com/content/skool.mov
A discussion by filmakers, not photographers on 30fps being bad.
http://prolost.blogspot.com/2008/09/so-close-canon.html

It's sort of been mentioned above but Vincent LaFloret's blog about actually using a 5DII to make a video and the discusion after is well worth reading. Bar all the repetitive comments about hosting.
Vincent absolutely loves the camera, but has never shot video before. So it's a very different story to those who know more about filmmaking/videoing, but may be resistant to change or know the problems that Vincent has yet to meet.
« Last Edit: September 21, 2008, 06:03:44 PM by jjj » Logged

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Ray
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« Reply #30 on: September 21, 2008, 07:26:30 PM »
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A discussion by filmakers, not photographers on 30fps being bad.
http://prolost.blogspot.com/2008/09/so-close-canon.html
[a href=\"index.php?act=findpost&pid=223107\"][{POST_SNAPBACK}][/a]

Dear me! There does seem to be a lot of confusion about the benefits of 24p.

I quickly skimmed through the comments in your linked thread and I could find no explanation as to why 24p could be better than 30p other than a possible frustration at a lack of equipment to handle 30p.

The point doesn't have to be laboured, if you don't have a display capable of accepting a 30p format, then it has to be converted to another format that the display can accept. If you also don't have the software or hardware to perform such conversion, then obviously you're in trouble.

However, as Jonathan has pointed out, whether it's 24p or 30p, most modern displays will accept both and both will look very similar because neither is displayed at a rate of 24 or 30 fps.

There's nothing magical about 24p, except that it's better than 24i. Filmic movies in the cinema are never displayed at 24 fps, but usually 72 fps. Each frame is displayed 3x.

It is possible, however, that some people will make a virtue out of a fault. 24fps is well below the flicker-free threshold. It lends itself to a slightly stuttery effect, more so than 30p. It's possible that a slight imperfection regarding smoothness of motion will trigger a nostalgia effect. Early movie projectors actually did project frames at 24fps.
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« Reply #31 on: September 21, 2008, 07:49:51 PM »
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Dear me! There does seem to be a lot of confusion about the benefits of 24p.
Such as

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There's nothing magical about 24p, except that it's better than 24i. Filmic movies in the cinema are never displayed at 24 fps, but usually 72 fps. Each frame is displayed 3x.
  !!??
And what are 'filmic movies'?



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It is possible, however, that some people will make a virtue out of a fault. 24fps is well below the flicker-free threshold. It lends itself to a slightly stuttery effect, more so than 30p. It's possible that a slight imperfection regarding smoothness of motion will trigger a nostalgia effect. Early movie projectors actually did project frames at 24fps.
[a href=\"index.php?act=findpost&pid=223125\"][{POST_SNAPBACK}][/a]
Actually it was 18fps as base rate, though it could be varied for effect and 16fps is minimal level for flicker free images [for humans].
Though why lets bothersome facts get in the way.  
And if 24p give a certain look, that people like for what ever reason, let them use it.


This from the comments as to what has been feature requested from Canon in the blog I linked.
"1. Offer the option of 29.97 and 25.00 fps instead of just 30.00, because when you import any frame rate that's not exact as expected in an NTSC or PAL timeline, the video editors usually resample (instead of re-timing) and this creates ghosting in the final. Only Vegas has a manual way, and AE through a plugin, to fix this -- other editors don't. So this 30.00 is a dangerous option to have for editing, especially as most people don't know about this.

2. Offer 24.00 (film) and 23.976 (IVTC film) as options too. I specifically told him that these frame rates are very important to indie filmmakers and without them none of them would consider this product.
« Last Edit: September 21, 2008, 07:59:41 PM by jjj » Logged

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Ray
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« Reply #32 on: September 21, 2008, 08:01:53 PM »
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In contrast, one of the engineering challenges of designing LCD displays has been to make a pixel that can react fast enough to meaningfully display higher frame rates. Unlike a CRT, an LCD pixel does not fade to black between scans--it continuously displays a color until the next frame arrives, and then it fades fairly smoothly from the old color value to the new one. How long this process takes is defined by the response time of the LCD. The response time of the LCD also limits the maximum frame rate the LCD can display. A high-speed photograph of an LCD display will not show any black band in the image the way a CRT will. Each pixel is illuminated 100% of the time.

[a href=\"index.php?act=findpost&pid=223078\"][{POST_SNAPBACK}][/a]


Jonathan,
That's broadly my understanding of the differences between CRT and LCD also. We both know that LCD monitors that are used for still image processing need not have a fast response time. For moving images they do. This has always, until recently, been a disadvantage of the LCD for moving images with fast action, particularly sports. Early LCD displays used to have a falling response time of 15 or 20 milliseconds. I believe they are now as low as 3 or 4 milliseconds.

But you can't have it both ways. A sluggish response time would certainly counteract and blur a stuttery effect. However, an extremely fast response time will have the opposite effect; will accentuate the jerkyness.

I'm not aware of any display that is operating at a refreh rate of 24 fps. Can you point me to a link that explains how this occurs and what the benefits are? As I've already mentioned, even a movie projector in the cinema projects those frames at a rate of 72 fps. If the LCD display holds each of those frames for close to 1/24th of a second, the eye will detect the abrupt change to the next frame. If the liquid crystals have a persistence that smooths the transition, then that's not good for fast action. You get the trailing effect of a poor response time.
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Ray
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« Reply #33 on: September 21, 2008, 08:42:31 PM »
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And what are 'filmic movies'?

Movies recorded on old-fashioned film. (Hey! Couldn't you work that out   ).

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Actually it was 18fps as base rate, though it could be varied for effect and 16fps is minimal level for flicker free images [for humans].

It might well have been 18 fps in early technology. Before we had motor cars we used to ride on horses. That's not relevant. But I am surprised at your statement that 16 frames per second is the minimum for a flicker-free image. I've never heard of such a thing. Can you point me to some authoritative source where this is stated?

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"1. Offer the option of 29.97 and 25.00 fps instead of just 30.00, because when you import any frame rate that's not exact as expected in an NTSC or PAL timeline, the video editors usually resample (instead of re-timing) and this creates ghosting in the final. Only Vegas has a manual way, and AE through a plugin, to fix this -- other editors don't. So this 30.00 is a dangerous option to have for editing, especially as most people don't know about this.

And I can't play either 24p or 30p satisfactorily on my WinXP 64 bit system using the latest Windows Media Player, but I don't whinge about it. There's clearly something wrong, missing or incompatible in my 64 bit system, but my Vista Ultimate O/S on my laptop handles both formats fine so there's no problem.

"Please Mr Canon give me a frame rate of 29.97 because my video editor can't do a good job."    I mean, how ridiculous is that? Talk about the tail wagging the dog!!
« Last Edit: September 21, 2008, 08:46:11 PM by Ray » Logged
Jonathan Wienke
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« Reply #34 on: September 21, 2008, 08:47:15 PM »
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I'm not aware of any display that is operating at a refreh rate of 24 fps. Can you point me to a link that explains how this occurs and what the benefits are? As I've already mentioned, even a movie projector in the cinema projects those frames at a rate of 72 fps.

A film projector has the same problem as a CRT monitor--the frame must be blacked out while the film is advancing from one frame to the next. This means that the image is not constantly being displayed, but is flashing on and off. The shutter is simply cycled multiple times per frame so that the flash frequency is too high to be perceived as a flicker. With a 24p LCD HDTV, there is no flicker to disguise--each frame is displayed continuously, fading into the next frame without a flicker-causing transition to black between frames. The only effect the internal refresh rate has on the displayed image is to affect how long the display takes to transition from one frame to the next.
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Ray
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« Reply #35 on: September 21, 2008, 09:13:32 PM »
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there is no flicker to disguise--each frame is displayed continuously, fading into the next frame without a flicker-causing transition to black between frames. The only effect the internal refresh rate has on the displayed image is to affect how long the display takes to transition from one frame to the next.
[a href=\"index.php?act=findpost&pid=223140\"][{POST_SNAPBACK}][/a]

Fading into the next frame...?? Sounds like that would be just fine for a slow moving rustic scene and a gentle breeze. However, you can't have any fading from one frame to the next during fast action. Even though those liquid crystals remain illuminated to some degree all the time, that illumination has to be low in a high quality LCD display suitable for movies, otherwise the contrast ratio would be too poor.

It seems to me, whether or not there is a total momentary black-out between each frame, there has to be a sudden transition from one image to the next during even moderate movement.

But let's for a moment suppose you are right. What advantage does 24p have over 30p? This is the only reason I got into this thread because I got the impression that some people think that 24p is a better frame rate. It's certainly not better for PAL countries. Canon HD videocams like the HV20 that do 24p in America, do 25p in Australia and Europe because PAL is a 50Hz system.
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Ray
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« Reply #36 on: September 21, 2008, 11:53:20 PM »
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Ray (and others who are interested), let me help you a little in understanding why the 24fps from cinema cameras are not a coincidence at all and why it still matters at what frame rate we view movies.

A long time back in filming history it was experimentally determined that movement could be shown smoothly using 19 frames per second. Many silent films are shot using that speed. Played at modern 24fps these all look like "funnies", but at the time they came out they looked "normal". Now one may wonder why a speed of 24fps was chosen later. After all it would only cost more film while actual motion smoothness wasn't helped significantly. It so happened that by doing experiments it was discovered that a light flicker rate of 48Hz had a strong effect on people looking at it. They seemed to be more open to the emotional storyline of the movies they were watching, which made going to the movies a much stronger experience. Why this was the case was not known at the time, but it made the "dream industry" settle for 24fps, each frame projected two times (not three!) so the flicker rate was 48Hz. Only later on it was determined that the human brain has a strong tendency to sync to light impulses. It so happens that 48Hz is the typical rate of alpha waves in the brain: the very same waves that can be measured when we are dreaming... And yes, even looking at a white screen with a 48Hz flicker will open up your deeper feelings. ("Saturday night at the movies, who cares what picture you see?" as the song goes.)

Do I need to go on or can you do the extrapolation of using other flicker rates than 48Hz yourself?
[{POST_SNAPBACK}][/a]

Sounds impressive, EDp, almost convincing, except you seem to have a few statements which don't accord with purported facts that are easily accessible on the net. Can you quote your sources?

A quick Google search produced the following, from
[a href=\"http://www.web-us.com/brainwavesfunction.htm]http://www.web-us.com/brainwavesfunction.htm[/url]

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The next brainwave category in order of frequency is alpha. Where beta represented arousal, alpha represents non-arousal. Alpha brainwaves are slower, and higher in amplitude. Their frequency ranges from 9 to 14 cycles per second. A person who has completed a task and sits down to rest is often in an alpha state. A person who takes time out to reflect or meditate is usually in an alpha state. A person who takes a break from a conference and walks in the garden is often in an alpha state.

The frequency of alpha waves are even slower than 24fps, never mind doubling to 48fps. The fastest waves are beta waves, up to 40Hz, characteristic of a person engaged in strong debate, such as taking on the President or Prime Minister in parliament. Is this the state of average movie goers, lounging in their comfortable seats in the theatre?

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These beta waves are of relatively low amplitude, and are the fastest of the four different brainwaves. The frequency of beta waves ranges from 15 to 40 cycles a second. Beta waves are characteristics of a strongly engaged mind. A person in active conversation would be in beta. A debater would be in high beta. A person making a speech, or a teacher, or a talk show host would all be in beta when they are engaged in their work.

You are right, however, that a mere doubling of the 24 fps to 48 fps is often used for filmic movies. But 72 fps is sometimes used and I guess could be considered more hi tech.
« Last Edit: September 22, 2008, 12:01:53 AM by Ray » Logged
Ray
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« Reply #37 on: September 21, 2008, 11:59:40 PM »
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and 16fps is minimal level for flicker free images [for humans].
Though why lets bothersome facts get in the way.  
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jjj,
To get back to this issue, could you please check your facts first, otherwise you are in danger of misleading folks.

This is what Wikipedia has to say on the matter.

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Generally, the frame rate of 16 frames per second (frame/s) is regarded as the lowest frequency at which continuous motion is perceived by humans.

This not the same as claiming that 16 fps is flicker-free. There is a huge gulf between a perception of motion and a flicker-free perception of motion.
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Ray
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« Reply #38 on: September 22, 2008, 01:22:19 AM »
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Just in case anyone reading this is interested in getting technical, there's an interesting discussion I came across doing a Google search, which addresses this issue of exactly how 24p footage is handled on a modern LCD display.

 http://www.avsforum.com/avs-vb/showthread.php?t=832822

No-one seems to know, but there's lots of speculation. This thread from last year, ends with the question along the lines, 'do we have any TVs that display true 24p (presumably at 24Hz)?'

The latest LCD TV displays mostly have a fixed refresh rate of 100Hz and 120Hz, but precisely how 24p footage is displayed seems to be a secret.

It's a subject which I'm interested in because in the near future I will probably succumb to the lure of an HDTV set. Australia will also soon stop broadcasting standard analog definition. I'm totally undecided whether to get an LCD, Plasma or projector. At the moment, the newly announced Epson TW-5000 (7500 in the US) looks very appealing on paper.

Oh! I almost forgot. I'll also need an HDTV display to get the most out of my 5D2  
« Last Edit: September 22, 2008, 01:42:15 AM by Ray » Logged
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« Reply #39 on: September 22, 2008, 09:37:22 AM »
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If it's necessary to convert the frame rate of video footage to a higher frame rate for the sake of smooth motion, then its better to start off with 30p rather than 24p.

If I've got that wrong, please be specific.
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Ray and Jonathan,

I think you're both right.24fps does flicker---when shown on analog equipment or crt display at 24fps. So does 30fps.  That's why interlacing works on CRT displays it essentially turns 25fps into 50fps (by showing 50 1/2 frames per second).  I'm used to NTSC which is 60 1/2 frames per second and when I view PAL at 50, I see flicker until I'm used to it.

But the point is that an LCD does not redraw the whole frame by blacking out and showing a whole new frame every 1/24th sec.  It just changes pixels that change every 1/24th sec.  And the pixels stay lit almost all the time, ie. they are not black 1/2 the time.  So there is no flicker at 24fps.  There is motion judder though.  These new LCD tv's with 120hz refresh rate are interpolating frames and inserting them to eliminate motion judder.  Most filmmakers would rather their viewers turn off this feature and watch at 24fps without adding pulldown and additional frames.  Actually they don't care as long as the dvd is paid for

I have 24 fps video on my web site.  It does not flicker on my LCD display.  It shouldn't, I don't think there is a "refresh rate" for LCD displays.  On my CRT display it plays at 24fps even though my CRT is set to 80hz and refreshes 80 times per second.  It doesn't flicker there either, and it saves bandwidth, allowing a higher quality picture using the same data rate. than 30fps.
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