P3D IMAX 3D

[aifxtony@xxxxxxxxxxxxx (Tony Alderson)]

>Boris Starosta (digest 2758) Reviewed: Into the Deep

>I did not perceive any flicker at first, though later I saw a little
>"jumpiness" in bright objects moving rapidly across screen.<

I suspect this was strobing from the frame rate, not stereo ghosting.  You
can see this artifact in horizontally (rapidly) moving objects in most
movies. You need to get up to Showscan frame rates to eliminate this.

>The show did have one technical error, however - what I thought was a
>pretty severe vertical misalignment. It was hard to judge on the big,
>featureless screen, but I would guess that the left image was being
>projected some one to two feet higher than the right image. I spoke with
>the projectionist afterwards, who revealed that the vertical alignment
>adjustment mechanism on the projector was inoperable, and that they could
>do nothing about it until a technician came down from Canada to fix it.<

Holy Cow! That's a lot of vertical disparity.  I'm glad you spoke to the
projectionist; most of the audience probably didn't have any idea what was
wrong.  If nobody complains, the theatre may assume it is not a serious
problem.

>I'm not sure I would have shot the thing (or at least edited it) in quite
>the same way.<

I might not either, but let's not forget IMAX is accumulating a lot of
experience in shooting and presenting big screen 3D.  It can be a little
difficult contradicting them when one's own experience is a much smaller
format to a much smaller, and more specialized audience (i.e., we're all
stereophiles) IMAX plays to a paying, generalized audience, and has to turn
a profit.  This certainly affects their evaluation of trade-offs.

>So I think a large fraction of the audience probably felt discomfort on
>some of the extreme close-up shots. This was worsened by some jumpy
>editing - say, cutting from an extreme close-up of a little squid, to a
>medium shot of fish. However, the jump from medium distance (2ft.) to
>infinity was not a problem - a testament to the great liberating power of
>"windowless" stereo.<

I think you have a good point, but the eyestrain was made a lot worse by
the vertical misalignment.  It's been awhile since I saw this show, but I
don't recall much discomfort myself.

>Knowing what I do now about projection (which is still precious little), I
>would have "fixed" the extra close-up shots in post processing to move
>them back a little from the viewer. I would do this simply by shifting the
>images together a little bit, maybe somehow during the editing of the
>master negative. I think the result would have been slightly
>non-orthoscopic: the tiny subjects would have looked a little larger, and
>a little farther away (comments, anyone?). <

In theory, this is a not a bad suggestion, but in practice, it turns out to
be not quite simple.  You can't correct image misalignment in editing. This
process is just cutting apart and resplicing bits of film.  You can't shift
the image there.  It is obviously impractical to adjust the alignment
shot-to-shot during projection of the movie.  So this can only be done by
optical printing to make a new dupe negative, which could be spliced into
the rest of the neg.  This is difficult, expensive and costs some image
quality (by expending another generation).  So producers don't like  to
take this step unless it is REALLY necessary.

Also, there is strong pressure in commercial 3D to get things way off the
screen.   Audiences seem to demand it, and it's hard to blame them.  This
is, after all, part of the point of 3D movies, isn't it? (Audience
immersion and interaction)  The key, I think, is to get the best effect
with the least eyestrain, and not overdo it.  When EVERYTHING is constantly
in your face, the gag loses its impact.

>In digest 2759, Mark Chapman commented:

>Imax places infinity at the screen instead of the window at the screen. <

This is one of the parts of IMAX philosophy that has always annoyed me.  It
seems they are throwing away a lot of usable stereo space.  Yet I can also
see how this greatly simplifies much of the production chain, and minimizes
projectionist error.  They seem to get away with it...they have such big
theaters, maybe no one misses the space behind the screen.

Tony Alderson
e-mail:  aifxtony@xxxxxxxxxxxxx



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