projection shutters, digital cinema and home consumer viewing

steve waschka · July 28, 2014

Anybody want to help me wrap my head around this...... I guess I'm trying to compartmentalize my efforts. For example: What are your thoughts on not having the black fractional frames you would have in a film projector? I know the two blade shutter was designed to not be noticed by the human eye. But I know we can perceive its presence. Are we missing it at home? I have read that some cinema projectors actually insert black space between frames. Is this true? Is it only between frames and not as a two blade would present a film? And then how can you take this into the home? Projection shutters are what like 25-33% of the open spaces so to have a screen process this work it would have to be really fast. Not possible? I think these are the kinds of things that get missed in the pitch to the average consumer by the marketeers trying to stay ahead of them. When inherently movie theaters may have a leg up on people buying 80" lcds at walmart for $800. How does cinema work? I really dont know. And if I dont know, the average household is just gonna buy the bluray. I believe digital projection is awesome for modern theater. And all of these shutter simulation and all the other magic I don't know abouf should be possible at that scale. But making a video on a laptop for a laptop appears to me to be futile to try to replicate a film experience. And im a believer in the single frame editing even on premiere pro. And yes it is a PIA. But maybe I wasnt listening when someone said making videos and editing on computer is cool. But it is not, nor will it ever be digital cinema. And Frame scanning your film for laptop is also cool. But then you are turning it into a laptop video. Again... not digital cinema. Who was it.... Greta Gerwig on "Side by Side" that said she sees people watch film on an iphone in the subway and says "Noooooooo". I just love the knowledge. And I try to incorporate anything I can to improve what I do. But some of this stuff is just not public knowledge. If it is I cant find it...

Edited July 28, 2014 by steve waschka

Chris Millar · July 29, 2014

What are your thoughts on not having the black fractional frames you would have in a film projector? I know the two blade shutter was designed to not be noticed by the human eye. But I know we can perceive its presence. Are we missing it at home? I have read that some cinema projectors actually insert black space between frames. Is this true? Is it only between frames and not as a two blade would present a film?

They don't 'insert' it as such, but it is there - it's integral to the idea of a (butterfly) spinning shutter. I think, one pull down per rotation, hidden in one of the 'wing' of the butterfly, the other shutter there both to better balance the shutters rotational inertia characteristics (off topic I guess) and to provide the extra flicker that meets with approval with an average viewer (for reasons of manifold complexity best not delved into by armchair perception psychologists).

I'm not sure of the shutter angles used - one might assume that it is as small as the fastest pulldown could achieve without damaging sprockets and so on, that way you could achieve maximum brightness on screen. But then maybe something more akin to a 180deg is better (which equates to two 90deg wedges on the actual shutter) for the optimum 'fuzzy-flickeriness-fudge-factor'...

Anyhoo, yeah, interesting point you make, as I understand it a pixel on screen pretty much refreshes it's state for all intents and purposes relevant to the topic 'instantaneously' - or at least with only intermediate sates between the frame to frame values i.e. >>no black state.

Could be wrong, interested to hear what others have to say on the matter ;)

steve waschka · July 29, 2014

I figured out how to hit the limits of my macbook pro's refresh using adobe's strobe effect. Change the color to black and tweek the timing. Even a 180 degree camera style shutter simulation looks bad. You can see the offset refresh pattern in the screen. Forget about a two or three blade shutter. It just cant process it.

Ive read the theater projectors made by Barco cache the image frame and run through a black frame in between image pulldown. It was single statement. Not a manual spec. And they didnt mention if it projects the same image twice to simulate a double shutter.

I have experimented with adobe and this wouldnt be hard to generate projection files using image sequences then the projector scans through a black frame space every image frame. It could be done. They could be doing it. But my software stops at 60hz. And my macbook pro struggles with true 60hz content even at SD.

Another problem lies in my software. The precision needed to generate the black space isnt there. You can type in .008366 as a value. But it will round it up to .01. Interestingly when you hold your mouse back over it it shows the .008366. But my Adobe itself maxes at 60hz files. It would be better if there were a frame space tweek. You could work with image sequences with that feature and replicate pretty much any projection scheme you want. Especially if newer software runs at faster playbacks than 60hz. But if the screens cant refresh fast enough then.......

Even then i'm experimenting. Amass all this equipment and effort to accomplish and then to say "no that sucks... go back to the other way" good knowledge but that would be a let down. I dont want the theater experience to just be a big projection. I would be disappointed.

Edited July 29, 2014 by steve waschka