6p laser projection offers many advantages for theatrical 3D such as high luminance and high contrast. 3D separation is based upon glasses that use two different sets of RGB filters to pass the 6 primaries to the left (RGB) or right eye (R’B’G’). In paper #66-1 at SID, RealD exposed some real performance problems with the current 6p glasses.
It is widely known that the 6p glasses are not coated for anti-reflection on the inside, which allows stray light to enter the eye and even the reflection of the wearer’s eyeball can be visible at times.
In testing that RealD did, the company found there is also a significant problem with the left lens. It has a very pronounced roll off in stereo contrast as a function of viewing angle. It is so bad that images viewed at more than about a 35 degree angle are essentially black.
Is this a practical problem? Yes and no. In standard theaters, the widest field of view is typically around 20 degrees, so you don’t see the adverse affect of the steep roll off that much. But in premium large format (PLF) theater, like IMAX, the viewing angles can increase to nearly 40 degrees. That means a person sitting in the front in the middle or left side, will experience the effect.
The photo below shows a comparison of this left lens at normal incidence and at 40 degrees for the 6p solution and for a polarization switching solution, such as the one offered by RealD. The color shift and loss of contrast is quite evident in the 6p solution, but is not an issue with a polarization solution.
Naturally, RealD would rather have theaters opt to continue to use the RealD polarization solution, but it does acknowledge the benefits of laser 6p in terms of 3D brightness. Nevertheless, improvements in the glasses are clearly needed for the PLF market, which also includes many theme park attractions as well.
The reflections from the glasses, along with the weight, were the main complaints from viewers at the 6P laser projection event that I attended at IBC last year. The performance on other aspects, though, was spectacular in most other ways. Having said that, I was in the ‘reserved for the press & VIPs’ section’ exactly in the centre line of the screen, so with no viewing angle problems. (BR)