"Why 3D doesnt Work"

From master editor Walter Murch via Roger Ebert's blog...

http://blogs.suntimes.com/ebert/2011/01/post_4.html

The biggest problem with 3D, though, is the "convergence/focus" issue. A couple of the other issues -- darkness and "smallness" -- are at least theoretically solvable. But the deeper problem is that the audience must focus their eyes at the plane of the screen -- say it is 80 feet away. This is constant no matter what.

But their eyes must converge at perhaps 10 feet away, then 60 feet, then 120 feet, and so on, depending on what the illusion is. So 3D films require us to focus at one distance and converge at another. And 600 million years of evolution has never presented this problem before. All living things with eyes have always focussed and converged at the same point.

If we look at the salt shaker on the table, close to us, we focus at six feet and our eyeballs converge (tilt in) at six feet. Imagine the base of a triangle between your eyes and the apex of the triangle resting on the thing you are looking at. But then look out the window and you focus at sixty feet and converge also at sixty feet. That imaginary triangle has now "opened up" so that your lines of sight are almost -- almost -- parallel to each other.

A more technical, than preferential reasoning against the 3D craze...
 
A more technical, than preferential reasoning against the 3D craze...

Maybe the gut dislike a lot of people have for 3D is because of this human visual quirk...

I can't see how it could be solved technically, but you never know.
 
Last edited:
When you set your shot with a shallow 3d depth of field where focus and convergence are at the same point, other things are out of focus and it should work fine. Granted, every shot can't do that, still...
 
I really like Disney Digital 3D where it just adds depth and nothing jumps out of the screen. It always looks perfect to me. Even if you take off the glasses, it doesn't look bad.
 
When you set your shot with a shallow 3d depth of field where focus and convergence are at the same point, other things are out of focus and it should work fine. Granted, every shot can't do that, still...
This is still unnatural, isn't it?

If I look at a salt shaker on a table and I then look past it to the
pepper shaker on the kitchen counter my eyes will focus on it. If
you shoot that scene in 3D, focus on the salt shaker and have the
pepper shaker out of focus as I sit in the theater looking at the
screen I can't see the pepper shaker in focus.

So the entire scene now looks unnatural in 3D. Great flat, but not
so good in 3D.

I always knew I didn't like 3D - this helps me understand why. And
I've never liked shallow DOF in 3D - that really gives me a headache.
 
Worst part for me is crossfades with items in each shot at different depths.

In avatar, right at the moment they fade away from the two making out... painful as the eyes try to account for the difference in convergence points between the shots. Had that happen in a science museum type film about paleontology as well.
 
Okay, I'm gonna reveal my secret to enjoying 3D. You can all thank me later.

Giant bong-rip.

:)

i only saw 2 movies in 3d, avatar and tron. I was stoned for both. Hated the 3d both times. It's really just pointless. gives me a headache. doesn't add anything to the experience, i think it takes away.

it wouldn't be as bad if the 3d actually had 3 dimensional SHAPE to it. Instead it just looks like multiple planes. maybe he addressed that in the article, i didnt read it.

hopefully this 3D thing is just a fad. again.
 
Here's a reply to Murch from The Atlantic Monthly (I don't know enough to judge the controversy):




Here's Murch's argument stated more concisely. For any light entering your eye (or your camera lens) to be a focused image then your eye lens has to be focused to the distance the light came from. Since all light comes from the scattering screen in a movie your eye must focus there. But steroscopic 3D relies on the eyes converging to different depths to see the apparent source of the light. Murch's claim is that we evolved in a world where the convergence point and focal point are always the same. Ergo we can't learn to like stereo 3D.

Sounds good but it's wrong, not just for one reason but two.

First, he's wrong about the focus. What he says is true only if your eyes had infinitely large and perfect lenses. For finite sized lenses the hyper focal effect dominates. What this means is that as long as the smeared out size of a defocused point source is smaller than the resolution limit of your vision (i.e. the blur circle of a perfectly focused spot) then the point is effectively in focus. In practice this happens for any object located far from you. For human eyes in a darkened room this might be something like 20 feet. If you are that far from the screen then, when your eyes focus on the convergence zone behind the screen, the screen itself is effectively still in focus. Thus 3D works for everyone who is not in the very front row.

Second, it's patently obvious that stereo-scopic vision does give a great 3D look. If you ever looked in one of those old view-master stereoscope you can see that not only was the object 3D but it was in focus as well. How does this Jibe with Murch then? Well Murch is mistaking two different things called a convergence zone. Your eye balls don't do the 3D processing, your brain does. It compares the two slightly different images to infer the 3D. It is your brain that is inventing the concept of a convergence zone not the eyeballs. Now for objects very very close to you, your brain will also notice that your eyeball muscle are pointing the eyes in a non-parallel way. And your brain may use this info as well. This is the physical eyeball sight line convergence that Murch is worried about, not the one that comes from the brain processing. And again for any object farther away than 10 times the distance between your eyes then your eyes are pointing nearly parallel and there is no sightline convergence info for the brain to consider. All that remains is the cognitive inference of depth and that works fine because that is EXACTLY how your brain was built to work.

Thus to the extent that Murch has a point it is these two: 1) don't sit in the front row. 2) film makers should not project the 3D objects out of the plane any closer than 10 feet from my nose for long periods of time. Other than that Murch is wrong.
 
After watching Avatar...it works. I get the science and evolutionary problems...but let's just say it's a great 'trick' to add depth (if done properly).
 
Avatar was beautiful except for that one spot... I think the PRETTY helped cover up the fact that it was just ferngully meets dances with wolves plotwise (or Jimmy Stewart in Broken Arrow if we look back to the 50's). I found my self looking all over the place in the frame to try to see more before the shot was over... eyes dancing more than in any other film I've ever seen.
 
Saying 3D doesn't work is a bit like saying root beer tastes gross.

It may be 90% washing up liquid, but if it tastes good, it tastes good.
 
Side tracked, sorry: I think the story of Avatar was hit too hard...I could name a hundred other great films that use the same plot device. It's what story-tellers do...tell a story that's been passed down through the ages.

I think they took that 'plot device' and used it just fine...just like a thousand movies before it.

OK, back to the topic at hand.
 
Side tracked, sorry: I think the story of Avatar was hit too hard...I could name a hundred other great films that use the same plot device. It's what story-tellers do...tell a story that's been passed down through the ages.

I think they took that 'plot device' and used it just fine...just like a thousand movies before it.

OK, back to the topic at hand.

I totally agree (Prisoner of Zenda was remade tons as was Robin Hood)... I recognize the same technical issues that Mr. Murch stated, but loved the 3D of Avatar... Lovely! Captivating!
 
So the entire scene now looks unnatural in 3D. Great flat, but not
so good in 3D.

Yeah I guess you're right.

Still, I've enjoyed all the recent 3D. I think they did a great job with Tron. I just saw the Green Hornet too. Not as well done (talking 3D now, of course pretty much everything wasn't that well done haha). It had a shot where they showed information being passed from person to person and it got complicated. The screen kept splitting in two with each person in his own window. It ended up being maybe 15 shots of different people in different locations at different distances from the camera all on the screen at once. That hurt. That's really the only "headache" moment I've had from the recent 3D.

Now some of the older stuff in the 90's and before when most of it was split by color.... that was guaranteed headache haha.

I still think it's going to be here for a while. It'll eventually loose it's "oooooh" factor, but will still be around.

Shoot, at the rate science advances we may be watching holographic movies, essentially 3D without glasses, in our lifetime... who knows?
 
Oh definitely Paul. I've seen some holographic videos on YT that will blow your mind (examples at trade shows and such). Images of light that you don't see through...seemingly solid. The problem is, the technology requires a pretty high tech triangulation rig...the quality ones.

The ones I've seen thus far are much larger than your home would support, but perhaps a theater in the round idea? The audience watches the movie from an amphitheater setup? Not sure how they would separate the BG from the image...in terms of forgetting it's in 3D space...a huge CU of a face might be odd in this medium...I suppose if everything around the viewing area was blacked-out, it could work.
 
Back
Top