Film-Tech Forum ARCHIVE: How can I get the perfect screen brightness

This is topic How can I get the perfect screen brightness in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Yinghong Wu (Member # 6908) on 07-02-2012, 09:20 PM:

HI,I am a projectionist who work in a digital cinema.Our cinema have five screen and our projector is Christie CP2000 ZX.I use lamp loc to calibrate the screen brightness.I find the screen brightness is dissatisfied,especially in 3d mode(our 3d mode is dolby 3d).Is there any way to increase our screen brightness.I know the screen brightness is the core in the digital cinema.But I have the limited knowledge about to calibrate the screen brightness.Thx.
[Smile]

[/B] [B]Christie CP2000 ZX

Posted by Chris Slycord (Member # 4239) on 07-02-2012, 09:53 PM:

Too many unknowns like size of screen (and if it's silver or not; and I know Dolby can be used w/ white but we can't assume it's white), the size/manufacturer/model of the bulb, the brightness you're getting in 2D and 3D. There are probably others I'm forgetting.

Posted by Yinghong Wu (Member # 6908) on 07-02-2012, 10:14 PM:

THX CHRIS，Our four screen is 7X5.25m,One is 12m wide.Our server is DOLBY DSS 100+DSP 100,Our screen is normal screen not silver screen，The bulb is CDXL30.And I don't know how to measure the screen brightness and how to calibrate it.

Posted by Monte L Fullmer (Member # 2797) on 07-02-2012, 11:23 PM:

If my metric to US measure is correct, the first three screens are 22.75 ft wide and the fourth screen is 39 ft wide.

The bigger screen could use a CDXL-40 for 3D.

Posted by Brad Miller (Member # 2) on 07-02-2012, 11:25 PM:

No it can't Monte. The ZX cannot handle that bulb.

About the only thing you can do is get a higher gain screen (I am assuming you have a standard 1.0 matte white)...or get a projector that is PROPERLY spec'd for that screen size.

Posted by Monte L Fullmer (Member # 2797) on 07-02-2012, 11:39 PM:

Sorry on that.

A BARCO DP2K-20C would definitely fit the bill for that wider screen.

Posted by Yinghong Wu (Member # 6908) on 07-02-2012, 11:52 PM:

THX Monte and Brad,I forget to say the 12m wide's screen use the cp2000sb cdxl 60 bulb silver screen which the screen brightness is ok.Anthor four screen is cp2000zx cdxl30 normal screen which the screen brightness is poor.So I will adopt Brad's suggestion and suggest our boss to replace these four screen with silver screen. [Smile]

I also want to know the right way to measure the screen's brightness thus I can know our cinema's screen brightness is standard.（what tool and method)

Posted by Chris Slycord (Member # 4239) on 07-03-2012, 02:08 AM:

The tool is a light meter. It'll measure the luminance, which in the industry is measured in foot-lamberts although in other industries/applications a different unit might be used.

Posted by Monte L Fullmer (Member # 2797) on 07-03-2012, 03:04 AM:

quote: Yinghong Wu
our boss to replace these four screen with silver screen.

No, you need a high gain matte WHITE screens for Dolby 3D.

It's the other 3D systems that needs the silver screen.

Posted by Yinghong Wu (Member # 6908) on 07-03-2012, 07:09 AM:

Thx Chris and Monte.I got it^-^

Posted by Gordon McLeod (Member # 33) on 07-03-2012, 10:20 PM:

quote"No, you need a high gain matte WHITE screens for Dolby 3D."

there is no such thing as a high gain matte white screen matte is unity gain to a little above high gain non silver screen is pearlescent

Posted by Carsten Kurz (Member # 5396) on 07-04-2012, 06:14 AM:

And certainly, unlike for RealD, a silver-screen is not needed for Dolby-3D, but can give you some extra kick on brightness if the owner or installer did a bad choice on the system layout. Plus, it offers you a choice to upgrade to a usually brighter-than-Dolby polarization 3D system later.

- Carsten

Posted by Steve Guttag (Member # 268) on 07-04-2012, 06:56 AM:

As Gord points out...there is no such thing as a "high-gain matte white"...that is like saying it is a large-small.

Biggest misconception going around the industry...gain screens make your image brighter...in fact, they make them darker. But wait you say...when I measure a high-gain screen in the center it really does get brighter...well yes...there it gets brighter...everywhere else it gets DARKER and unless all of the action is constrained to the 10-degree area in the middle of the screen...the image will be darker. The only way to really mitigate that is to curve the screen and "accept" the geometric distortions that brings (particularly with the current DCinema lenses...except Schneider).

Remember the spec is not just 14-fL in the middle (or 4.5fL for 3D)...it is the middle AND the sides, which need to be not less than 75% of the center (85% for screening rooms)...which can not be achieved on a flat screen with a gain greater than 1.3. Anyone putting in a flat gain screen of 1.4 or greater are out of DCI/SMPTE compliance.

Posted by Marco Giustini (Member # 4544) on 07-04-2012, 01:16 PM:

Silver screens are EVIL. I cannot understand how come polarized systems are so commonly adopted. Particularly flat silver screens in short throw auditoria are so incredibly bad. How is that possible that people do not realize that you have 14fl on center, but only 3fl on sides?

Posted by Pete Naples (Member # 761) on 07-05-2012, 04:28 PM:

@Marco

Where is the Facebook stylee 'like' button?!

I have tried this discussion so many times with customers hell bent on ruining their image with a silver screen, all I get is 'the glasses are 50p' [Roll Eyes]

Posted by Monte L Fullmer (Member # 2797) on 07-05-2012, 04:45 PM:

..thought studios are taking care of the cost of glasses issue to the cinemas...

True, in the long run Dolby is the way to go when it comes down to cost.

Posted by Marco Giustini (Member # 4544) on 07-05-2012, 04:45 PM:

it's indeed a problem, particularly for big multiplexes. I cannot think of cinemas recycling and sanitizing 3D glasses every day. But the silver screen is not an option either. If I had a cinema and really wanted the 3D (unlikely) I'd go for XpanD. Dolby is good, but glasses' quality consistency is simply not acceptable.

Posted by Olivier Lemaire (Member # 5579) on 07-05-2012, 04:51 PM:

In France, Silver Screen will be "prohibited" in the next 5 years (at least if you dare believing what a public sector entity may declare 5 in advance...) :
http://www.today3d.com/2012/03/france-kills-silver-screens-votes-out.htm

We will see that in 5 years...

Posted by Peter Castle (Member # 1997) on 08-14-2012, 06:33 AM:

I was looking for a topic involving screen brightness so as to avoid starting a new one and found this.
We're about to update our Series 1 projector to Series 2 and are increasing lamp size, mainly to accommodate brighter 3D. The problem is:
Can a screen be too bright?
With 2D advised to be 14fL, and 3D seeming to head towards 6fL, can screen brightness be too high?
How do you determine what brightness to run at? By sight, or by meter?
Any experience out there with high brightness screens?

Posted by Bajsic Bojan (Member # 4928) on 08-14-2012, 06:49 AM:

We've had the issue of a screen being to bright here (80ftL) and what i can say is that:

-colors are a bit shiny,
-image looses some contrast
-black is not black but a shade of gray

The post production guys that come here often with their test material thought it was too bright especially when running same material side by side with 35mm.

We eventually went from 3kW bulb to 1.2kW and changed out our 1.6 gain screen with matt white. Got 14-16 ftL and we're happy.

When setting up for the first time, use a spectroradiometer for color reproduction and luminance measurements.