Film-Tech Forum ARCHIVE: Recommended Screen surfaces for Laser

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Posted by Danial Simmonds (Member # 4638) on 07-19-2019, 01:06 PM:

Hi Everyone,

I would like to find out from anyone with experience on laser installs being laser phosphor or RGB, what type of screen surfaces has been used for 2D and 3D applications.

How acceptable is the speckle with a silver 2.4 gain if using it for dual 2D/3D? Or does clarux performs better with laser or do you really need screen shacker?

Is the Hi-White type of screens good enough for 2D with laser without screen shacker? What type of screen gains to limit in laser applications ?

Posted by Marcel Birgelen (Member # 6801) on 07-19-2019, 03:08 PM:

Most phosphor laser machines don't really have a lot of speckle and don't need any screen shakers at all.

I'm afraid that a 2.4 gain silver screen with RGB laser will yield some terrible speckle. Usually, the projector manufacturer can give you some lists of screens they tested and what countermeasures are necessary for RGB laser setups.

Barco, for example, claims that their 6P machines don't need screen shakers at all for most screen types. I've not yet seen them in production, but they claim the same for their new series 4 3P machines.

Posted by Andrew Carr (Member # 9264) on 07-23-2019, 12:13 PM:

Strong MDI has a new high gain surface for laser projection:

https://strongmdi.com/blog/introducing-premium-hga-1-7-screens-the-new-standard-for-laser-projection/

I've been told it will work for passive 3D applications depending on the application and media.

Posted by Muhamad Taufiq (Member # 8868) on 07-23-2019, 01:00 PM:

I'm not a technician, so please take my post with a grain of salt.

I have seen Barco 60L in 2 different cinemas, one with white screen and another with silver screen. The one with white screen, I can definitely see some speckle but most of the time there's no problem ignoring it. While the silver screen one definitely has a lot more speckle and it's kinda hard to ignore.

For Christie CP4325-RGB, so far I've seen it in 5 different cinemas, all with white screen. There's some variation between cinemas, but generally speckle is a bit less than 60L with white screen, almost not noticeable. I'm pretty sure this projector won't be installed in any cinemas around here with silver screen, so I can't comment how it will perform with silver.

As for Barco SP4K... well I'm still waiting for one to be installed.

P.S. I don't know whether any of those cinemas use screen shaker or not

Posted by Leo Enticknap (Member # 534) on 07-23-2019, 05:40 PM:

quote: Muhamad Taufiq
The one with white screen, I can definitely see some speckle but most of the time there's no problem ignoring it.

That was exactly my experience working in a venue with a 30L, too. It had to be a white screen, because film as well as digital projection had to be supported. The laser speckle was basically like changeover cues: if it's pointed out to you, you can't "undo" noticing it thereafter. But if it's not, most viewers notice the higher contrast range first and foremost, and aren't bothered by the slight speckle.

Posted by Marcel Birgelen (Member # 6801) on 07-24-2019, 12:23 AM:

quote: Muhamad Taufiq
P.S. I don't know whether any of those cinemas use screen shaker or not

It's indeed pretty impossible to tell without being able to look behind the screen or without being told. But afaik, Christie generally advises to install screen shakers with their RGB laser projectors. There are a few venues where it was seemingly omitted as the shaker setup seemingly doesn't work well with all screen configurations, especially uncommon geometry like deeply curved screens.

Those in charge of marketing those projectors are seemingly not so fond of the need of screen shakers for some configurations, that's probably why they try to keep a lot of information regarding their use under wraps.