3D movies start to fade

They're being screened at lower light levels than 2D films - and moviegoers appear to be noticing. Certainly, the professionals are. "On a technical level, it's fascinating," director Christopher Nolan tells The Wrap, "but on an experiential level, I find the dimness of the image extremely alienating." Here's the deal: A typical 2D film has an illumination of 14-foot-lamberts" - the unit of luminance by which screen brightness is measured. But a 3D system can lose as much as 80 percent or more of the light from a 2D system on the same screen.

[3D projection] displays two separate pictures, one designed for the left eye, one for the right. Some systems - for instance, projectors made by Texas Instruments - display the two pictures sequentially, in rapid succession; other systems, such as Sony's, display the pictures simultaneously. Both systems then use glasses to merge the two images into one three-dimensional image. But whichever system is used, the immediate result of dividing the picture into two images is that, in Lipton's words, "You lose half your light, because half the light goes to one eye and half goes to the other." Instantly, a 14-foot-lambert image is reduced to seven.

As The Wrap illustrates in the above chart, the percentage of opening weekend revenues from 3D screens keeps dropping. The reasons for this probably go beyond the brightness of the screen (having to shell out an extra two or three bucks could be a factor), but whatever the cause it can't be great news for an industry that seemed to be counting on the 3D craze as a significant revenue stream.