Light-loss in 3D cinema – how is that linked to High Frame Rate?

I’ve titled this post with a question to which I don’t know the answer. I apologise for that. It seems some people are suggesting there might be a link:
Mark Kermode Uncut
From a first-principles point of view, I can’t see why there would be a link. I have witnessed a presentation of The Hobbit: An Unexpected Journey in 48fps (a.k.a. HFR), and the image was pleasantly bright to my uncalibrated eyes. On the other-hand, it was a LieMAX (IMAX Digital) show, so it’s a very big screen to fill with light. Consider that the venue uses two separate projectors, which probably means that each projector is dedicated to showing the left and right eye images.
The talk from the (so-called) expert about triple-flash and double-flash, and the numbers quoted for number of flashes per second is all correct but redundant. The rates exceed the Flicker Fusion Threshold by a large margin, such that the number of flashes per second (in that range) is irrelevant.
I’ve watched 3D presentations on various types of Digital Cinema projectors. Systems that use varying solutions to the problem:

  • Those that use one projector and show the frames in the order LRLRLR, with a timed polariser (RealD) or filter (Dolby) to separate the images. Minimal light loss.
  • Those that use one projector to form the images stacked on the same imaging device, and a complicated lens (with polarisers) to superimpose those images on the screen. Requires more light input, and sacrifices spatial resolution for both 2D and 3D shows. The manufacturer used to claim this was better, but I was unable to find any evidence of this after exhaustive reading and research. The manufacturer’s name rhymes with ‘phoney’. I did notice this claim was quietly dropped once the projectors started selling.
  • Two completely separate projectors, each showing the image for one eye. Uses polarisers to keep the images separate. Minimal light loss with this approach also.

I think the best solution to not having enough light on-screen, is to push more light in to the system, so that more of the light reaches the screen. If techniques such as water cooling, and specially-coated infra-red-blocking filters are required to achieve this, then spare no expense. Cinema will always be a premium environment. If you are at the cinema, and think the image is too dark, don’t just sit there and put up with it. Find the manager and tell them.

Season’s greetings.

PS. I am not looking forward to the next Avatar film, except to see if the director can make it better than the first. You can have 24, 48 or 60 frames per second of junk, and it will still be junk.



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