Christie Considers High Frame Rate
August 8. 2012, Siggraph, Los Angles—We talked with Larry Paul from Christie about high frame rate projectors for cinema. The changes in projection will be as significant as those from film to digital, and will focus on perceived image resolution.
This transition is being driven by the oncoming changes in cinema from 2k to 4k or 8k resolution. This change will require another retooling and forklift upgrade to many theaters, many of which are still working on the relatively recent change to digital. An alternative is to change the frame rate from the traditional 24 fps to a higher rate.
The original rate is the slowest that will allow sync of audio and images and shows the least visible flicker. The driver at the time of adoption a century ago was cost, a faster frame rate uses more film per second, and over a 2-hour movie it adds up. In addition, the faster frame rates caused more film breakage, a serious problem when most projectors are unattended for a bulk of the showing time.
The good news is that the existing infrastructure is upgradeable to higher frame rates with just a firmware change. The current inventory of digital projectors are all capable of much higher rates because the image rate has no moving parts, and the images are files on a hard drive.
Tests with higher frame rate projection indicate that people perceive the images as being much sharper and exhibit far fewer aberrations than the same material shown at 24 fps. Since the eye and brain have to perform much less interpolation from image to image, the overall impression is that the picture is of higher quality. The problems of motion blur, object jitter, and color shifts are minimized at high frame rates.
The remaining technical issues for HFR include determining the next-generation rate; 48, 60, 90, or 120 frames per second. Even higher rates are possible, but there is a point where diminishing returns come in. They have run tests with projectors running at rates up to 1000 fps, and found that there is a threshold where further improvements were not observed.
The transition to high frame rate would not be as difficult as that to digital, because many theaters already have digital projectors. Increasing pixel count and changing frame rate both effectively double resolution. The pixel count does it in space, while the HFR does it in time. Both tracks to improve image resolution will require more storage, but the faster frame rate would use less additional storage than the increased image resolution. A faster frame rate increases data density linearly, while increasing pixels per frame increases data density by n2.
The primary limitation to change to higher frame rates is the lack of content. Just as people complain that there is no reason to buy a 3-D TV, high frame rate movies will have to wait for the movie industry to make more movies. In that respect, the release of "The Hobbit" may be the groundbreaker film, as "Avatar" was for 3-D. The first movie to be released in HFR will benefit from a filmmaker already known for understanding the genre and the basic storyline.