At last year’s CEDIA, we saw a prototype of a dual projection solution capable of showing HDR images. This product was launched in Europe, but at this year’s show, it was officially released to the U.S. market with the support of DCI Central.
According to R&D Director Domenico Toffoli, the demonstration is basically the same as was shown last year. It consists of two projectors, which are modified Sim2 SuperLumisPro models, which were stacked in a rig that includes very fine mechanical adjustments to align the two images.
Toffoli was showing The Great Gatsby movie, which was a good choice as people have seen this in HDR and is a good reference point. The images looked quite similar to other HDR demos I have seen of this movie – but Sim2 was generating this from an SDR Blu-ray disc!
According to Toffoli, the Blu-ray signal was simply split and sent unaltered to each projector. One projector is dedicated to showing the higher luminance values and the other to the lower luminance values, preserving the black level. If these projectors had only been superimposed, it would not be an HDR solution as they would merely shift the total contrast range up by having a higher peak white but also a higher black level.
To overcome this and create a real change in the contrast, the lower luminance projector was modified in the optical path in order to reduce stray light with new dedicated electronics to differentiate the video processing inside the two projectors. In a projector, that typically means the addition of apertures and baffles, so that may be what he is doing. The final contrast ratio of the paired solution was not revealed, but the images on the screen definitely had that “HDR look”.
Taking an SDR signal and creating an HDR image in real time is not easy, so this method will never be as good as one where a colorist is involved. In essence, the electronics in the projectors need to stretch the existing dynamic range of the content to the new dynamic range. Toffoli said he played with this quite a bit but finally ended up with a new gamma curve that is pretty close to the 2.4 gamma used in cinema. Note, this does not use the PQ curve specified in ST-2084 for HDR content. These are also 1080p projectors that combined create 6800 on-screen lumens.
The solution is available now in the U.S starting at $120K. – CC
