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» Film-Tech Forum   » Operations   » Digital Cinema Forum   » Poll - Digital Projection Framing - in the real world

   
Author Topic: Poll - Digital Projection Framing - in the real world
Adrian Hauser
Film Handler

Posts: 44
From: Sydney
Registered: Mar 2008


 - posted 06-10-2010 12:09 AM      Profile for Adrian Hauser   Author's Homepage   Email Adrian Hauser   Send New Private Message       Edit/Delete Post 
Hi Film Tech,
Can you please help me in a POLL on digital film screen presentation.
I am consulting on an upcoming Live action 3D Feature Film and require some
real world statistics on digital screen presentation.

In particular when receiving DCP's from distributors a digital projection framing chart is provided for most "big ticket" releases. I would like to know how many of your digital screens can show the whole framing chart without having to crop or mask actual picture content.

There is a concern from 3D content creators that a large number of cinema screens cannot or do not actually show this full frame. This can be due to a number of reasons, a projectors inability to correct key-stoning, poor lens selection and poor projection setup.

The inability to show the full image area can have drastic effects on the perception of the 3D content and post production methods employed to create a nauseating Free experience.

I offer two Poll options below which you can paste into your reply. Please if possible also provide a reason for ( if option B ) why the content cannot be shown correctly.
(Alternately answers can be sent to me personally at  - where users can remain anonymous. Personal and company names will not be used in my findings. It is for personal research only into creating better 3D content.)

A. Our Theatre is able to and does project the Full 3D Image area without Masking in Both
1.85 Flat 1998x1080
and 2.39 Scope 2048x858

B. Our Theatre is not able to project the Full 3D image area.
Reason.

Thank you for your time.
Adrian Hauser

[ 06-10-2010, 12:14 AM: Message edited by: Brad Miller ]

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Demetris Thoupis
Phenomenal Film Handler

Posts: 1240
From: Aradippou, Larnaca, Cyprus
Registered: Apr 2001


 - posted 06-10-2010 10:08 AM      Profile for Demetris Thoupis   Email Demetris Thoupis   Send New Private Message       Edit/Delete Post 
DC projectors do NOT correct keystoning, to set one thing straight. One solution is to tilt the projector in order to have the lens in a straight path with the light beam and thus do not loose any light. This though most probably will cause excessive keystone effect especially in humongously tilted theaters due to stadium seating. The other althernative which I prefer for various reasons is to keep the projector straight and lens shift the lens to bring the image to the screen limits. This option I prefer first o all because when playing Flat content in Scope format (DCP is in Scope but uses Flat ratio) then the lines at the sides of the content are straight and not sloped. I think that one particular theater which suffers the most of this is Odeon Leicester Square in UK since the height of the booth forces one to tilt the projector in extreme angles. That being said though, considering the screen uses the standard aspect rations 1.85 to 2.39 (if I remember correctly DCP scope content is 2.39 and not 2.35), then the lens shift is the best solution and will not screw up any framing problem. The worse is when companies believe that Scope movies are meant to be shown in 1.85 ratio to offer the top/bottom screen exit effect (used in G-Force). For some theaters that might be valid but most theaters who use the correct common height screen for flat and scope movies is not a good thing.
Demetris

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Brendan Penny
Expert Film Handler

Posts: 121
From: Bundoora, Australia
Registered: Dec 2008


 - posted 06-10-2010 04:15 PM      Profile for Brendan Penny   Email Brendan Penny   Send New Private Message       Edit/Delete Post 
I agree with Demetris, keep the projector level with only a slight down tilt to match the rake of the screen and then lens shift. This eliminates key stoning significantly which is half the battle of cropping.

Now, the biggest problem we face is with heavily curved screens. What do you do at the bottom of the screen. You either set the image so the frame just touches the middle bottom which leads to some small non image pockets bottom left and right or you bring the image down until the entire screen is filled but by time this is done you are cropping the bottom middle of the screen.

1st method allows the entire image to be projected but the exhibitor won't like it, they don't want any part of the screen not used even if its a foot of black at the bottom corner.

2nd method fills the screen but some cropping is present.

How does everyone deal with this issue? Are people still building curved screens for all digital locations? I notice Harkness say you don't need to curve a 140 screen for d-cinema but what about 180 and 220 surfaces?

Adrian, there is no yes or no answer to your poll. Every cinema presents different challenges. Don't wander too far from your safe area!!

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Adrian Hauser
Film Handler

Posts: 44
From: Sydney
Registered: Mar 2008


 - posted 06-10-2010 06:44 PM      Profile for Adrian Hauser   Author's Homepage   Email Adrian Hauser   Send New Private Message       Edit/Delete Post 
Thanks for the Replies.
How about this. Instead of reporting on your own screens, What percentage of screens in your locality do you think would be capable of screening a 3D DCP as a full edge to edge, with all 4 corners of the frame visible on-screen? (less the padded unused 2k area for 1.85 releases that only use 1998 pixels of the 2048 image.)

I have noted in some Feature release projectionist instructions that implicitly request that the entire "picture frame" is viewable regardless of Keystoning. Do you abide by these requests?

Thanks,
Adrian

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Mike Olpin
Chop Chop!

Posts: 1852
From: Dallas, TX
Registered: Jan 2002


 - posted 06-10-2010 07:04 PM      Profile for Mike Olpin   Email Mike Olpin   Send New Private Message       Edit/Delete Post 
Let me read into your intentions a little bit, I'm sorry if I missread.

The reason I think you are wondering about the charts is that a 3d object in positive space (appearing closer than the screen) cannot intersect the edge of the screen. If it does, the viewer will receive two conflicting depth cues. One cue from the stereopsis effect telling them the object is closer and the other cue from the known position of the screen relative to the viewer, telling them the object is at the same depth as the screen itself. This might be a contributing factor to discomfort and headaches some people associate with 3D.

Unfortunately, I believe a large percentage, at least half, of digital screens are over cropping slightly. A lot of screens have a slight curve. Some auditoriums were built with incorect aspect ratios, and the owners didn't care to fix them when the transition to digital occured.

I would recommend that a positive 3D object be treated the same as titles or other important compositional elements. Give it a "safe area". Make a rule that no object within 3 percent of the screens edge should ever enter positive space. That should keep you safe for most theaters.

Also as a side note, most of the day to day projectionists at theaters do not have the training or the tools to make changes to the DCinema image, and as a result, almost never run the included charts.

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Adrian Hauser
Film Handler

Posts: 44
From: Sydney
Registered: Mar 2008


 - posted 06-10-2010 08:51 PM      Profile for Adrian Hauser   Author's Homepage   Email Adrian Hauser   Send New Private Message       Edit/Delete Post 
Thanks Mike,
You read my intentions correctly.
Part of the last process of creating a 3D feature is to perform a convergence pass over every scene. This process is to help guide the viewers attention to appropriate the Depth Cue within the 3D shot. Ie to minimize constant eye strain moving up and down the z axis over cut points. So... sometimes you have to put someone's shoulder, for example, into the auditorium.

There is a tried and tested method to reduce the effect of this edge violation with the use of floating windows. These windows, per eye masks, perceptually bring the screen edge forward to minimize the conflict.
However if 'most' 3D screens are masking this area the audience will get headaches which makes it most important for projectionists to use these guides.
3D will not take off until some of these discomfort factors are addressed.
One thing for us to try is to add our own additional edge masking to compensate for this.
Im trying to work out what percentage of screens out there display 3D content without additional masking. This will influence our post process.

One of the other main factors is ghosting introduced by certain projection systems but i'll leave that to another post.

thanks ,
Adrian

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