James Cameron's 'Avatar' - The next gen of cinema

Lashout_UK said:
That's not how it works Neil, in the case of stereoscopic 3D films like Avatar :)

The 'full' 3D image you see (at 24fps, the same as the 2D version) through the glasses is composed of two distinct sets of images, both of which are projected (and synchronised) at full rate (24fps) - so if you close one eye, you're simply seeing one of the two images projected at you at full rate :)

If you look over your glasses during the presentation you can see the two separate images :)

I'm not quite sure how DLP projectors work these days - with old film projectors each frame would be exposed twice to give 48fps, which is fast enough to give a flicker-free image, but with DLP projectors there is no flicker, so presumably 24fps is enough to display smooth motion. Few things are actually filmed, and displayed, at 48fps - and it requires specific hardware to do so.

I don't know about the lag aspect - but I guess it depends on what you see it on. Some hardware could be doing some up or downscaling, or working hard, that creates the effect you see - I'm not sure. Can't say I noticed myself!
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It's not done this way any more.

These days, only one projector is used at a framerate of 144fps. The projector alternates between displaying left and right eye images, and does so three times, so that infact each frame is displayed 6 times (3 times for each eye).

A special filter is placed infront of the lens, in sync with the projector. This flicks between clockwise and counter-clockwise circular polarisation, and polarises each frame accordingly. I think this filter used to be similar to shutter glasses but now it's some sort of chemical element which reacts according to light changes, and flips its polarisation accordingly.

Each eye on the glasses is designed so that each eye can only see one type (Clockwise or counter-clockwise polarised light).

So in essense, if you were to close one eye, you would still be seeing 24 fps, but each frame would be shown three times for a total of 72fps. :)

Edit: As stated, this is how RealD does it, and they're the most commonplace in cinemas...
 
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Xenoxide said:
It's not done this way any more.

These days, only one projector is used at a framerate of 144fps. The projector alternates between displaying left and right eye images, and does so three times, so that infact each frame is displayed 6 times (3 times for each eye).

A special filter is placed infront of the lens, in sync with the projector. This flicks between clockwise and counter-clockwise circular polarisation, and polarises each frame accordingly. I think this filter used to be similar to shutter glasses but now it's some sort of chemical element which reacts according to light changes, and flips its polarisation accordingly.

Each eye on the glasses is designed so that each eye can only see one type (Clockwise or counter-clockwise polarised light).

So in essense, if you were to close one eye, you would still be seeing 24 fps, but each frame would be shown three times for a total of 72fps. :)

Edit: As stated, this is how RealD does it, and they're the most commonplace in cinemas...
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Slight issue there, FPS and refresh could be confusing.

You could refresh an image 144 times a second, but may only show 1FPS.

So the refreshes really are not important, what I'm getting at is, maybe, just maybe you're still only getting 1/2 the amount of FPS (per eye) with 3D.

So if you close an eye, with a 2D film you might get 24FPS, but possible with a 2D film, you're olnly getting 12 FPS.

I doubt this is the case, but you never know...

I guess the question is, if you close an eye at a 3D show, in 1 second, how many distinct different frames (not refreshes) are you getting. And likewise at a 2D showing.

A 3D film would have to show at 48FPS to be comparible to a 24FPS 2D movie - ignoring refreshes.
 
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NeilFawcett said:
Slight issue there, FPS and refresh could be confusing.

You could refresh an image 144 times a second, but may only show 1FPS.

So the refreshes really are not important, what I'm getting at is, maybe, just maybe you're still only getting 1/2 the amount of FPS (per eye) with 3D.

So if you close an eye, with a 2D film you might get 24FPS, but possible with a 2D film, you're olnly getting 12 FPS.

I doubt this is the case, but you never know...

I guess the question is, if you close an eye at a 3D show, in 1 second, how many distinct different frames (not refreshes) are you getting. And likewise at a 2D showing.
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*I believe* you still get 24 frames in a second.

For a single frame, there is two versions of it. One for the left eye, one for the right. The projector uses a "left, right, left, right, left, right" sequence for each frame.

I think some older systems use the technique you're thinking of, which in a 24 fps video, they will alternate frames and polarisation together. So frame 1 would be a left eye image, frame 2 would be for the right eye, frame 3 for the left eye, and so on. I think the newer RealD system has two seperate images for each frame.
 
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Xenoxide said:
*I believe* you still get 24 frames in a second.

For a single frame, there is two versions of it. One for the left eye, one for the right. The projector uses a "left, right, left, right, left, right" sequence for each frame.

I think some older systems use the technique you're thinking of, which in a 24 fps video, they will alternate frames and polarisation together. So frame 1 would be a left eye image, frame 2 would be for the right eye, frame 3 for the left eye, and so on. The newer RealD system has two seperate images for each frame.
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Ah! That sort of makes sense. So same number of FPS, just he 3D one has two versions of each frame and flicks/refreshes between each one 2-3 times.

Still recon the 3D looked a little jolty with fast moving stuff... Any, probably just my imagination!
 
IMAX 3D is quite old tech, before we knew how to synchronise projectors with shutters or Z-Screens. ;) They also use linear polarisation instead of circular, so if you tilt your head the picture will be blurred. This doesn't happen with RealD or Dolby3D.

I think the reasons for lack of adoption of Dolby3D are cost and size. It uses some weird prism wheel thing which must be installed within the projector, rendering a lot of older projectors incompatible due to their size and configuration. Also the glasses cost more to make, so cinemas are more hesitant to give out more expensive glasses.

I must admit, I don't really know much about Dolby3D as I've never played around with it... :)
 
NeilFawcett said:
Still recon the 3D looked a little jolty with fast moving stuff... Any, probably just my imagination!
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Perhaps this was down to the depth of field? The common problem with 3D systems (That has always existed) is that they still use 2D cinematography techniques for 3D films. For example, a shot of someone speaking will have a very shallow depth of field, ie. the head in focus but the background blurred.

The problem is that isn't how our eyes work. When we look at something, we focus on it, and everything else becomes blurred. However when you then go to look at something else, your eyes adjust, causing that to come into focus instead. You can't do this with a movie though as you are restricted to focussing on what the director was focussing on.

This is especially prevalent in action scenes where a lot is happening, and your eyes are constantly seeking around to see the whole picture as it's happening, rather than simply focussing on a head or something. This is pretty much the cause of eyestrain and headaches in 3D movies these days.
 
Xenoxide said:
I must admit, I don't really know much about Dolby3D as I've never played around with it... :)
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Well Dolby doesn't use polarisation, the main upshot of which is the screen doesn't need to be replaced/made silver and the end result is a bit brighter than RealD.
 
NeilFawcett said:
Ah! That sort of makes sense. So same number of FPS, just he 3D one has two versions of each frame and flicks/refreshes between each one 2-3 times.

Still recon the 3D looked a little jolty with fast moving stuff... Any, probably just my imagination!
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Wasn't just you, there were a couple of scenes where it was pretty juddery to my eyes too.
 
Just got back from watching it. Really good film but 3D was unnecessary.

Female smurf was hot and want human/alien sex with her
 
Watched it on Weds at the IMAX in Manc.

What a stunning bit of cinema that was! Set the standards that has.
 
Saw it for the third time on Tuesday at the BFI IMAX. Was sat at the side and fairly near the front because you need to book your seats, and the 3D wasn't as good as the two times I saw it at the Birmingham IMAX where we were sat bang in the middle. Definitely makes a difference!
 
Yup ^^

First time i saw it was at the BFI IMAX slap bang in the middle and the 3D was immense. Second time was in the local cinema right at the side at the front and the 3D was pretty poor.
 
saw it last night and thought it was spectacular

how people can call it depressing , i dont get

def set a new level in film making for others to aspire too
 
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