Film-Tech Forum ARCHIVE: Screen: Common Height or Common Width?

my profile | my password | search | faq & rules | forum home

»	Film-Tech Forum ARCHIVE » Operations » Digital Cinema Forum » Screen: Common Height or Common Width? (Page 8)

This topic comprises 13 pages: 1 2 3 ... 5 6 7 8 9 10 11 12 13

Author

Topic: Screen: Common Height or Common Width?

Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 06-02-2014 09:11 PM

The problem is that stupid 1.9 ratio chip. The chips SHOULD be 2.4 ratio. End of story. 90% of all movies are scope these days anyway. Series 3 equipment should standardize on that and the industry should start switching over to that standard.

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 06-03-2014 06:37 AM

quote: Carsten Kurz
Nothing 'is happening', Steve, you're making something up. No one confirmed putting scope at 11, no one endorses that. But the spec has a range, and no one ever believes that the idea behind the spec is that all formats have to come down at 14fL all the time.

I'm not making anything up...I'm looking your and other words...and just in that statement you issue the incorrect phrase that no one believes all formats should be at 14fL all of the time. That is PRECISELY what the film makers believe and what the goal is. No movie is EVER tested at 11fL (or 17fL for that matter) to see what the negative effects will be at the extremes of the theatre range. You could argue what the point of the spec is to allow the +/- 3 fL and I would agree with that. However, historically, there is an acknowledgement that theatres in the field, without other supervision, will stray from the optimal for a whole litany of reasons...mostly financial others from a practicality of a theatre's ability to have the resources to adhere to a more stringent spec. In Hollywood, theatres are checked before each screening...clearly not something the typical theatre owner can do.

The flaw in the specification, as it is currently written, is highlighted in this discussion in that the movies are NOT tested at the extremes to know just how detrimental they are. Nor are the full ramifications checked because most theatre designers and installers get the whole light on the sides versus center thing and put in these 1.4 and 1.8 gain screens to save on light...when in fact, they are darkening the picture as they hold the center at, apparently, 11, in some circumstances.

A clue to how important 14fL is to current digital projection is in the review room spec... .7fL...tighter than film. If one strays from it much, the blacks turn to grays, or the detail in the darker parts are lost. Also, as technology improves...the direction of the light is only going to go up...it is already happening with 3D...but even with film there has been a desire to get the white point over 20fL.

quote: Carsten Kurz
Features are mastered AT 14fL with the assumption that theaters MIGHT be as low as 11 or as high as 17. That's what's behind the +/- 3fL spec.

While it may be your assumption they are assuming that may be the case...but they aren't. That is the flaw.

quote: Carsten Kurz
DCI neither mandates the use of anamorphics nor constant width screens. So integrators have to work with a small, very limited equipment market that has been established so small because of the same spec.

A specification does not specify the path one takes to attain the result...just what the result should be. Anamorphics are a tool that are available to anyone to use. If you have a common-height screen, then they are the best tool to having a brighter scope picture and longer lamp life (or at least more stable during its life). The closer you keep the current demands between the formats, the better it is for lamp. The only reason anamorphics are not used more than they are has to do with cost. They are roughly $10K US per screen by the time you have it automated to move in/out. The other one is the myth that they are somehow non-DCI compliant. Nevermind that EVERY DCI projector thus far can handle them (allow for a 1.25 squeeze on the imager). Plus the DCI text is such that one has to be free from visible artifacts...of which an anamorphic in a cinema isn't visible from the seats (if you can see the pixels, then yes you will see they are wider than tall...but you will also see a lot of other "artifacts too not related to the anamorphic).

quote: Carsten Kurz
Over- or underlighting should be judged based on the projector/lens in use, perceivable contrast/ambient lighting, screen quality, etc.

I'm with you there.

quote: Carsten Kurz
DCI could have easily mandated the use of anamorphic lenses for common height screens if they'd wanted it. There is a reason why they didn't.

You are incorrect there...it isn't the spec's job to specify the method to the end-result. Perhaps with lasers, we won't have the issues we do with xenon matching the light on both formats...perhaps a different technology all together will evolve...who knows...why would one tie themselves to the technology of the day? That would be a poorly formed specification to state one were to use Anamorphics or DLP or such. Even those things like SMPTE 292 (HDSDI) was mentioned in the spec...it was more of an "if you use this method, then you will need to take security precautions) sort of thing...it never ties the hands of future technology nor stipulates this is the only technology to be used. Unfortunately, that spec did cause the biggest grief with using HDSDI as the transport medium for the picture...the dreaded Enigma module that has caused far more lost shows than keeping unauthorized copies of movies from being shown.

Brad, while I agree with you on the 2.39 imager...it does necessarily make the light less efficient with the current technology. Light tends to start in a roundish form...getting it to fit a rectangular opening generally wastes a lot of light...again, perhaps lasers will work towards this.

For those with the dreaded common width screens...which represent the VAST majority of all cinemas in use and being built today, we get a great light disparity again, but this time making flat the darker picture.

| IP: Logged

Carsten Kurz
Film God

Posts: 4340
From: Cologne, NRW, Germany
Registered: Aug 2009

posted 06-03-2014 06:51 AM

quote: Steve Guttag
No movie is EVER tested at 11fL (or 17fL for that matter) to see what the negative effects will be at the extremes of the theatre range.

As I wrote before, Steve, mastering takes place at 14fL, and theatrical is allowed to be 11 to 17, because that range is considered acceptable perceptually for the mastering centered at 14fL. If it wasn't like that, the spec would be 14fl +6/-0.

quote: Brad Miller
The chips SHOULD be 2.4 ratio

It's clear that, especially in the beginning of digital cinema, there was no efficient lightsource to support an imager aspect ratio like this. And I don't think it's there now. There are a few LED devices for projection with a specific 16:9 etendue/ratio built in.

http://www.luminus.com/products/PT-120.html

But I don't think this is possible with laser sources yet. Maybe they'll find a way with clustered laserdiodes at some point. The current fibre transmission for 3p/6p LIPs won't support that I guess.

You would have the same issue as you have with the way scope and flat are done now - a lot of wasted light.

- Carsten

| IP: Logged

Scott Jentsch
Phenomenal Film Handler

Posts: 1061
From: New Berlin, WI, USA
Registered: Apr 2003

posted 06-05-2014 09:16 AM

quote: Brad Miller
The problem is that stupid 1.9 ratio chip. The chips SHOULD be 2.4 ratio. End of story.

It's baffling as to why 2.4 wasn't done to begin with. It's not like home theater and business projectors with DMD chips were using the 1.9 aspect ratio.

There must have been a reason, such as yields on the manufacturing process or something...

| IP: Logged

Carsten Kurz
Film God

Posts: 4340
From: Cologne, NRW, Germany
Registered: Aug 2009

posted 06-05-2014 01:33 PM

They could have easily done 2.35 on the imager level. The problem is to build an efficient rectangular light source for that aspect ratio. Think back 15 years when it started and how low the light efficiency of early projectors was. No way they would have wasted even more light with native 2.35.

- Carsten

| IP: Logged

Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 06-05-2014 01:53 PM

It's a valid point, but they could've also done a 1.2:1 ratio and required everyone to use a 2x anamorphics. They could've had slight pillarboxing for the silly flat ratio.

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 06-05-2014 07:54 PM

They pretty much did start there. They used 1.25 chips (Since SXGA was current then) and 1.9x Anamorphics.

I agree tha the 1.8963 chips make little sense from an intended final ratio standpoint.

| IP: Logged

Carsten Kurz
Film God

Posts: 4340
From: Cologne, NRW, Germany
Registered: Aug 2009

posted 06-06-2014 05:13 AM

At the time DCI took up pace, they probably didn't consider anamorphics and non-square pixels state-of-the-art technology for the digital future of cinema.
With a standard for anamorphic lenses in it, a call for non-square pixels on the container level would also have been a logical step. I guess they simply wanted to get rid of that stuff, lens adjustments,lens movers, drift etc.
No scaling, no jaggies, no aliasing, just 1:1 pixel from DI to projection.

- Carsten

| IP: Logged

Bobby Henderson
"Ask me about Trajan."

Posts: 10973
From: Lawton, OK, USA
Registered: Apr 2001

posted 06-06-2014 10:09 AM

The problem with the current approach is it's just too much like HDTV at home. The 'scope format is smaller/lower quality than the flat format.

The first generation of d-cinema did support anamorphics, but the imaging chip was just too low in resolution (not to mention the video being played wasn't the greatest of quality either).

IMHO, for the next generation of projectors and delivery formats (because we all know this stuff is going to change and change again since change is the only constant with digital) they need to shift to an anamorphic design that makes 'scope the biggest format once again.

DLP chips with a 2048 X 1536 resolution for 2K and 4096 X 3072 for 4K would have more efficient lens and light coverage than the current rectangular chips. A 1.8x anamorphic squeeze would yield a 2.39:1 aspect ratio.

| IP: Logged

Mike Blakesley
Film God

Posts: 12767
From: Forsyth, Montana
Registered: Jun 99

posted 06-06-2014 11:19 AM

quote: Bobby Henderson
IMHO, for the next generation of projectors and delivery formats (because we all know this stuff is going to change and change again since change is the only constant with digital) they need to shift to an anamorphic design that makes 'scope the biggest format once again.

They need to come up with a change like you mentioned to make scope the highest quality size, but they also need to come up with a "retrofit kit" to put it into an older machine for, say, 10 to 15 grand. There's gotta be a lot of stuff in a projector that could still be usable, such as lens, power supply, cooling system, lamp system, etc etc.

If the only upgrade path is by replacing the whole projector at full price, it's going to be a lot harder to get every theater in the country to upgrade than it was to get them to go to digital in the first place. Most places are apt to wait until it's absolutely necessary (and that's the time when we will REALLY see a lot of smaller places go out of business since there won't be a VPF program this time).

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 06-06-2014 02:53 PM

You are going to want to make that squeeze 2.0:1 if you are going to be that close to it. From a scaling/artifact standpoint, doubling/halving is much more palatable from an end result. The original systems used a 1.9 "Scope" lens and 1.5 "Flat"

However, lets not forget...anamorphics are CURRENTLY available at a mere 1.25x but almost nobody uses them because they add about $10K to the bottom line (give or take). What makes you think they will go to them in the future? Especially since so many theatres are built for constant width nowadays (which won't take advantage of an anamorphic).

| IP: Logged

Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 06-06-2014 04:33 PM

The industry just needs to abandon 1.85
Problem solved. [thumbsup]

| IP: Logged

Lyle Romer
Phenomenal Film Handler

Posts: 1400
From: Davie, FL, USA
Registered: May 2002

posted 06-06-2014 05:04 PM

quote: Scott Jentsch
It's baffling as to why 2.4 wasn't done to begin with. It's not like home theater and business projectors with DMD chips were using the 1.9 aspect ratio.

My guess would be that it has something to do with the resolution of film scanning. On a 35mm film negative, 1.85 is taller than super35 scope.

My assumption is that when super35 film was scanned the width of the frame was 2048 (for 2k) and 4096 (for 4k). Therefore, the scope image was defined to be 2048x858 for 2k (double both for 4k).

Next, I can only guess that flat wasn't quite that tall but they bumped it up to 1080 pixels tall (double for 4k) to be compatible with HDTV. The width of flat was then whatever the math calculated to with a 1080 pixel high image.

Therefore, super35 is confirmed to be the root of all evil. After ruining scope on 35mm film, it also ruined scope in digital cinema.

I could be wrong but I think the vast majority of scope films were shot on super35 at the time DCI was being defined so specifying scope to match super35 would make some sense.

What they should have done (and still should do) is make the chip 1080x2592 (2k) and 2160x5184 (4k). Common height screens would just pillar box flat and no lens zoom or light adjustment is needed. For crappy common width screens they can just letterbox scope in the flat image and you get the same benefit of no adjustments between formats.

| IP: Logged

Jonathan Goeldner
Phenomenal Film Handler

Posts: 1360
From: Washington, District of Columbia
Registered: Jun 2008

posted 06-06-2014 09:16 PM

quote: Brad Miller
The industry just needs to abandon 1.85
Problem solved.

I approve this statement.

| IP: Logged

Terry Lynn-Stevens
Phenomenal Film Handler

Posts: 1081
From: Toronto, Ontario, Canada
Registered: Dec 2012

posted 06-06-2014 10:37 PM

quote: Bobby Henderson
The 'scope format is smaller/lower quality than the flat format.

If scope images were simply delivered in squeezed anamorphic and theaters were required to have an anamorphic lense then there really would be no discussion. The 16x9 chip is really the best of both worlds, if a theater uses an anamorphic then 100% light efficiency is being used for scope and something like 96-99% is being used for flat (I can't remember the exact spec). Everyone wins if the whole sensor is used.

quote: Bobby Henderson
they need to shift to an anamorphic design that makes 'scope the biggest format once again

The only way to get the entire use of the full 16x9 sensor is to use an anamorphic lense (this is current, no need to change the projector spec), this is only way to the full 2048 x 1080. It is the delivery of the scope DCP image that is the problem.

| IP: Logged

All times are Central (GMT -6:00)

This topic comprises 13 pages: 1 2 3 ... 5 6 7 8 9 10 11 12 13

Printer-friendly view of this topic

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.