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A Technical Review: Alice in Wonderland 3D
A Technical Review: Alice in Wonderland 3D

From the perspective of Mike Levi, President of DPI

Last weekend, my family and I attended our 3rd 3D film is so many months - Alice in Wonderland. This review will not focus on the performance of the actors, or the entertainment value of the story, or even the success or failure of the film-makers application of 3D technology. Rather, this review will focus on the implementation of 3D technology within the commercial cinema auditorium where we watched the film.

In short, the venue was not up to the task of properly presenting 3D entertainment due to two major problems.

The first problem was that the theater geometry was not conducive to an immersive 3D experience. The screen was only 22’ wide, yet the first row of seats in the stadium seating section was at least 35’ from the screen. Since the first, second and third rows were well below the bottom of the image, we sat in the 4th row. That placed us at the bottom of the projected image, but roughly 45’ from the 22’ wide screen.

I have to admit, I expected the 1.85 screen to morph into a scope aspect ratio before the movie started. Had I done a bit of research in advance of going to the theater, I could have learned that Alice in Wonderland 3D was presented in 1.85:1. That being the case, the screen did not morph from 22’ wide to 28’ wide, so we found ourselves sitting nearly two times the image width from the screen. That is too far away to become immersed in 3D content. The small and distant screen consumed only a fraction of my field of view. That would be fine for watching TV, but it was marginal for cinema viewing and even worse for viewing a 3D film.

My normal rule of thumb is to try to sit 2.5 to 3 times the screen height from the image. Given the size of the screen and the geometry of the theater, there were only two rows of seats that would have met my rule of thumb, and those seats were below the bottom of the screen so they would have left us all with sore necks. The unbelievable point being, in this particular auditorium, 90% of the seats were not conducive to conveying immersive 3D entertainment. Not surprisingly, my 3D experience in this venue was underwhelming, to say the least.

The second problem was the brightness produced by the cinema projector / screen combination. It was bright enough for the 2D content that preceded the 3D feature – I estimate it was putting about 14-16 FtL of light on the screen, but when 3D started rolling and we all put on the glasses, the image was unacceptably dim. It was so dim, in fact, that it destroyed the integrity of the film. I found myself constantly flipping the 3D glasses on and off, just to see how bright the image actually was. There were a lot of dark scenes with muted colors in the film, and with the glasses on, those dark scenes and muted colors looked like a muddy haze. There was no discernable dark area detail. Even bright scenes with colors that were intended to be highly saturated with high luminance looked dim and underwhelming.

In short, the under-powered projector / screen combination created inadequate dynamic range to convey what should have been a very dynamic trip through Alice’s fantasy. To me, this was unforgivable. The screen was only 22’ wide, so there was no reason that the image should have looked so dim. Sadly, everyone who paid $10 to watch Alice in Wonderland in that theater, on that day, was a victim of the theater company’s maintenance neglect or cost savings strategies.

Here is a little publicized, but very important fact: when we view content in 3D, the light that reaches our eyes is approximately 20% of the light that would reach our eyes if we were watching that same content in 2D. The reasons for this significant loss of brightness relate to a variety of factors, but the biggest consumers of light in the 3D photon path are:

    • The increased frame rate of the source and the projector, which increases the number of dark periods between frames (double the frames, double the dark periods). This temporal reduction in illumination has a direct impact on what we see. In simple terms, when a projector spends less time producing light on a screen, the light reflecting from the screen is reduced.
    • The increased length of the dark periods between the frames. This is required to insure adequate temporal separation between of the left eye and right eye content, which helps to minimize ghosting. Again, increasing dark time results in fewer lumens leaving the projector.
    • The 3D glasses we all wear. Even the best 3D glasses only transmit about 45% of the light our eyes would normally see. Less expensive glasses may only transmit 40%.

Add the compounding effect of these three major factors, plus the impact of a few smaller ones, and in any 3D application, current technology dictates that what our eyes see will only be roughly 20% of the maximum reflected brightness the projector / screen combination are able to produce for typical 2D content. No doubt, the operators of the theater where I viewed Alice in Wonderland either did not understand this fact, or they did not care.

There is a simple lesson here. In order to create great 3D viewing, we need to have significant lumen / FtL headroom in our display / screen designs. A reasonable target would be to design 3D venues such that the projector / screen combination produces 50-60 foot lamberts for 2D content. If it is a theatrically dark venue, this would require reducing lamp power (or turning one lamp off) so as not to overpower our eyes, but when viewing 3D content, with lamp power restored, a premium 3D presentation is achieved.

Sadly, given the larger screens that are employed in most commercial cinemas, and the cost of replacing lamps more often (than is necessary for 2D content), the likelihood of going to a local cinema and being treated to an under-illuminated 3D presentation is pretty high. Add the risk of sitting in a theater with poor geometry for 3D immersion, and it becomes clear that enjoying consistently powerful 3D movies is likely to be hit and miss in a commercial cinema environment. I take heart in knowing that our 3D salvation is near!

With 19 spectacular 3D projection systems in our lineup, DP offers the projection technology to create amazing 3D theaters – even for venues with screens approaching 30’ wide. Of course, since these are our theaters, we can design the room to produce optimum 3D viewing geometry as well.

Personally, I look forward to the day when I can treat my family and friends to Hollywood’s latest 3D spectaculars, ESPN-delivered 3D sporting events and Discovery Channel 3D adventures, from the comfort and technical superiority of our own 3D home theater.

That day is coming very soon. Our local Best Buy is already selling 3D Blu-ray players... and I have a contact or two at DP.


Posted on Friday, April 02, 2010 (Archive on Monday, January 01, 0001)
Posted by mbridwell  Contributed by mbridwell

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