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The credits in Avatar just didn't look sharp, and when I looked without the glasses, both eyes were clearly separated and both showed obvious side weave.

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You answered the question when you took your 3-D glasses off. The side weave will affect the perceived focus (and also probably trigger a huge headache).

Labs have gotten worse at image steadiness over the years, and since the credits are often the very last element I'm sure they were rushed through the transfer to meet the printing deadlines.
 

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Posted by Hillary Charles (Member # 769) on 03-05-2010, 06:31 AM:
 
Side weave on an IMAX film? For a horizontally-traveling film, wouldn't that mean a serious projection issue?
 

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Posted by Tony Bandiera Jr (Member # 2365) on 03-05-2010, 12:04 PM:
 
Hillary, if it was caused by the projector, yes indeed. But since the feature was ok and the credits weren't, it is obviously a lab/printmaking screwup.

I have heard of the horror that happens when an IMAX film has a pileup.
 

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Posted by Sam D. Chavez (Member # 1841) on 03-05-2010, 03:00 PM:
 
I noticed the same thing at Regal Hacienda in Dublin, CA, a sideways jitter only on the cast, but this was only with glasses off at the end.

Maybe the whole print was doing this, but was not as noticeable as it is white letters on a black background.
 

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Posted by Dave Callaghan (Member # 1544) on 03-05-2010, 03:51 PM:
 
I can see how "side weave" - especially with the horizontal film motion through an IMAX projector - might be interpreted as a projector issue.

Just to clarify - sometimes in 35 mm the image shows side weave.

If you pull the aperture plate you can compare the perforations to the picture image. The perfs show the projector side weave - what is happening with projector control of sideways motion of the film base.

The image will either be the same (best case) or worse by a little or a lot. Any extra is side weave in the printed emulsion, which is a combination of what the lab might contribute and "what we see is what they got" after post-production.

I believe what I am seeing is image side weave as printed.

I have seen what happens when an IMAX projector loses the loop - sort of like the image is being shaken from side to side by an earthquake. Let's just say it isn't subtle.

I have also noticed the same lack of sharpness in scrolling end credits at the most recent AMC in Toronto projecting with SONY video projectors which ought to eliminate all film issues - or is this something to do with scrolling end credits?

In that case, I walked up to the booth and the credits looked sharp. Heading back down, focus appeared to hold until I was about a third of the way back to the screen.

I'm not trying to go off on tangents here by mentioning 35 mm and video, but while it was an IMAX film print, the picture source for Avatar was video and who knows about the end credits?

One of the last credits - which included all the sound logos - was a still image and it was sharp.

Another point - while the picture during the feature extended to the top of the screen - the scrolling credits did not. I was reminded of a flat trailer of a scope feature that maintains the aspect ratio with a broad hard mat.
 

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Posted by Hillary Charles (Member # 769) on 03-05-2010, 05:03 PM:
 

quote: Tony Bandiera Jr

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I have heard of the horror that happens when an IMAX film has a pileup.

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quote: Peter Castle

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RealD was readable without glasses while IMAX's two images were well separated. Is that related to linear and circular polarisation differences?

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Not at all. If the images w/o glasses looked pretty much "together" in realD and pretty "separated apart" in Imax, the explanation is probably the one underneath, but certainly nothing to do with the polarizion system used.

There are "no theoretical differences in performance" from both polarizing systems, linear or circular (or elliptical), other than with circular the extintion ratio is theoretically pretty independent on the position of the analyzer (that is, it doesn't matter much the rotation angle between the filter in the projection and the filter in the glasses). With linear it matters a lot.

That's in theory. In practice, the only differences between using circular and linear polarization due to current manufacturing methods are:

-Circular polarizers are slightly LESS efficient in light (say 1-2%)
-Circular has slightly WORSE performance in crosstalk (=worse ghosting, say 10x)
-Circulars are more expensive to manufacture (say 10-100%, but keep in mind they are dirt cheap anyway).

With circular, though, the crosstalk ("ghosting") performance remains pretty much the same on a wide range of head possitions while with linear it quickly becames worse-and-worse with each degree you tilt your head left-or-right.

I don't know in Avatar's precise case, but Imax 3D presentations have traditionally tried to minimize possitive parallax (=the image separation that makes stuff appear behind the screen) while allowing most of action to contain negative parallax (=the image separation that makes stuff appear in front of the screen).

Thus, most action in Imax 3D films have traditionally taken place in front of the screen. They can "get away with that" because the limits of the screen (the frame) on Imax theaters is (was) pretty much out of the field of vision of the viewer on such large screens.

Again, don't know in Avatar's case in particular, but traditionally, they would've taken such a 3D film and during the mastering to Imax they would've altered the registration to minimize possitive parallax and maximize (w/o going overboard) the negative one, thus "bringing most of the whole movie closer to the viewer and not so far away into the screen".

On one side they have to do it if some scenes on the film were shot pre-converged (most), as on such large screen sizes the possitive parallax (separation of far objects) can become magnified (with the screen size) to way over the maximum of aprox. 7cm(+a little angular divergence amount) we humans can adjust to.

On the other side, we are much more forgiving to negative parallax as we humans can easily cross our eyes "closer together" (converge, like looking at our own nose) but we can't easily move our eyes much "further apart" than parallel (we can't "diverge our eyesight" like trying to look at both our ears at the same time, with the right-eye pointing to the far right while the left eye points far to the left at the same time).

So perhaps they just readjusted the converge plane to bring Avatar closer into the "theater space" in Imax presentations and decided to do the same with the end titles (a bad choice, if you ask me).

We have to add the weave that all such mechanical systems have (even if small) as the film travels horizontally semi-independently on each view.

Maybe
 

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Posted by Gordon McLeod (Member # 33) on 03-15-2010, 01:34 PM:
 
My suspision is the weave is in the source material since all 15 perf printers run very slow and they are usually not the culprit
 

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Posted by Kyle Butler (Member # 5601) on 05-05-2010, 06:19 AM:
 
Weird.
Our digital 2D version did the same thing.
I can't recall how many times our door person called up to booth
"6 IS OUT OF FOCUS"
 

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Posted by Andy Linde (Member # 5664) on 05-24-2010, 07:15 AM:
 
I remember seeing Avatar in IMAX 3D and thinking the same when I saw the credits. As if the focus had slipped at the end or something.
 

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Posted by Marco Giustini (Member # 4544) on 06-07-2010, 03:21 PM:
 
The side weaviness is something I noted in London at the BFI Imax when I saw Oceans 3D, during credits. Don't remember if it could be seen during entire movie though.
 

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