Film-Tech Forum ARCHIVE: 3D Screen Paint

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Posted by Paul Trimboli (Member # 1509) on 10-06-2003, 08:55 AM:

What type of paint can be used to painted a screen for polarised 3D projection? I know IMAX paints their screens, they apply the final coat on site. Well they did on the IMAX here in Perth, the plans for the theatre say so. Where can I purchase such paint? Anyone in Australia sell it?

Posted by Ray Derrick (Member # 1001) on 10-06-2003, 09:07 AM:

Try Entertainment Services, they have done most if not all of the Imax installs in the Asia-Pacific.

Posted by Greg Mueller (Member # 17) on 10-06-2003, 09:25 AM:

Hmmm
I was under the impression that the silver "lenticular"(sp?) screens had a special embossing to their manufacture that made the polarized light behave in a specific way. Is that just salesman talk?

Posted by Gordon McLeod (Member # 33) on 10-06-2003, 09:28 AM:

To my knowledge there are no perferarated lenticular silver screens made in a long time
They were popular in the 50's (raytone and miracle mirror)
Cinemecaninca used to have one in the 70's and I think it is no more
The standard 3d screen nowdays is smooth
Technicote used to sell 3d screen paint
many contractors used aluminum outdoor barn paint back in the 70's sprayed on in very light coats as it will eat the vynal if applied too thick

Posted by Andrew Lee (Member # 1330) on 10-06-2003, 02:48 PM:

Before this gets blown out of proportion, let me state the following:

- For light to maintain an acceptable level of polarization on reflection, the surface must be metallic (aluminum, silver or magnesium).

- Making, spraying, or even attempting to make a decent 3D coating will take about 10 years off your life.

- The only lenticular 3D screen available is from MDI in Quebec and has been available for the last year. (Gord, I must show you a sample next week when I am in town) As you know a lenticular surface prevents hotspotting and also results in higher polarization performance. I won't plug MDI's product on this site but will discuss technical issues from this point.

Greg, if you can find a better performing 3D screen I will fly to Washington myself and install it for you.

Paul, no one sells 3D screen paint to my knowledge. Please feel free to dabble around with store bought aluminum paints. Make sure the paint is a "non-leafing" type of aluminum, otherwise the gain will be too high and will not work well.

Good Luck

Posted by Greg Mueller (Member # 17) on 10-06-2003, 02:54 PM:

Yep
MDI that's what I bought down at ShoWest.
Still haven't put it up yet

Posted by Gordon McLeod (Member # 33) on 10-06-2003, 03:01 PM:

Glad you are doing a lenticular one I always loved the cinemecanica ones and was so unhappy when they dropped the line
When I worked for Stan Ash along time ago I painted many screens and it isn't pleasant

Posted by John Pytlak (Member # 331) on 10-07-2003, 07:58 AM:

Is there an established test to determine how effective the screen surface is in maintaining polarization? [Confused]

I assume you would just project one eye with its polarizer, then measure the extinction ratio through the viewer's polarized lens. What is an acceptable ratio to avoid double images and eyestrain? 10:1, 100:1?

Posted by Paul Trimboli (Member # 1509) on 10-07-2003, 08:06 AM:

When you say it will take 10 years off your life, do you mean becuase it is poison or becuase it is time consuming? How does IMAX do it?

Posted by John Pytlak (Member # 331) on 10-07-2003, 08:12 AM:

Proper safety equipment (respirator, goggles) should always be used when spray painting, expecially large areas like a screen. [Eek!]

Posted by Andrew Lee (Member # 1330) on 10-07-2003, 11:56 AM:

Paul, what I really meant to say is that trying to produce an acceptable 3D screen surface is an extremely difficult and exasperating task. There are so many factors involved in getting metallic paints to behave in order to get a surface that has the performance you require, aesthetic appearance, and absence of defects (stripping, lacquer blush, etc.). The ten years I mentioned was due in part to the stress and endless attempts over the years. As mentioned by others, these paints are not the most healthy substances to be around during application. Masks should be worn at all times when applying metallic paints, water-based or not. Imax screens up to a certain size are manufactured and painted at MDI with a propriatary paint. After a certain size, the screen is painted on site by Imax personel with a robotic paint rig.

John, in my 18 years of dealing with aspects of 3D projection, there have been a few attempts at standardizing a test for 3D screen performance. The method you briefly outlined is the way myself and others use. Off-axis polarization performance is also checked as well. Just remember that an LS-100 Minolta spotmeter is the best toll for the job for two reasons. This meter has the resolution at the lower end to give you the extinction readings you require and also the meter is not polarization sensitive as other meters are (any lightmeter that uses a beamsplitter or a mirror to reflect the incoming light to the meter's photocell has the potential to give you false readings when used in conjunction with a polarizer).

As far as an acceptable contrast ratio, or signal to noise for a 3D screen, its subjective at best. There are screens out there at 50:1, 80:1 and so on. It is my experience that 150:1 is what you should be shooting for. At this level, combined with efficient and aligned polarizers, aligned on-screen images, balanced light sources, equal print densitys, and a filmaker who knows what he is doing, eye strain and ghost images are virtually eliminated. No simple task.

Posted by Dick Vaughan (Member # 540) on 10-08-2003, 02:29 AM:

having just completed alignment checks and signal /noise measurements on our IMAX screens in Bradford and` London Science Museum we are getting figures between 180:1 and 190:1

Posted by Frank Angel (Member # 248) on 10-08-2003, 11:02 AM:

Perhaps Jeff Joseph can explain the many factors that were in play with the Egyptian Theatre setup because ghosting was rarely evident in any of those screenings (and I saw almost every one of the shows and from a variety of seating positions). Even as a kid I remember the ghosting problems with films in the 50s. At the 3D Expo, except if you tilted your head, the ghost problem was simply not a factor. They must have been doing a lot of thing right.

I read the claims the Fox made about their lenticular silver screen (the Miracle Mirror) that hotspots were not a problem and the use of it was part of the CinemaScope spec. The silver surface was needed for the extra gain, but the lenticular treatment prevented what would be severe hotspot and light fall-off if a flat silver screen were used. The fact that once again we have a silver lenticular screen available is a real advantage. I am in need of a screen replacement and this seems like just the ticket because I am slightly underlit on that screen and the gain of a silver without hotspotting will save me from having to consider new lamphouses. Thank you MDI.

I recall that is the screen material that comes in a FedEx box, right?!! How awesome.

Frank

Posted by Andrew Lee (Member # 1330) on 10-08-2003, 01:05 PM:

Sorry Frank, MDI can't fold 3D screens just yet.

One reason for the lack of ghosting these days is that the quality of the polarizers available is far superior than what was in use yesteryear.

Although I was not there, by all accounts Jeff and the people involved went the extra mile to present good 3D. [thumbsup]

Posted by Jeff Joseph (Member # 511) on 10-08-2003, 11:12 PM:

Well, we had a least two secret weapons:

Dan Symmes, who's been playing with 3-D since "Stewardesses" days, was there to help us set up, and was there for every show, headphones ready, to speak to the booth staff.

And we had Paul Rayton and crew in the booth. I can't stress enough how important it is to have qualified personnel doing this. In addition, we had someone (a second projectionist) watching the screen at all times.

The 3-D films of the 1950s sometimes had slight framing issues from shot to shot. If one camera was slightly loaded "off", then every time we cut to a scene like that, we're slightly out of frame. So that had to be watched constantly.

And we rehearsed, both sound and picture, numerous times.

Jeff

Posted by Ken Layton (Member # 133) on 10-09-2003, 12:01 AM:

Technikote makes screen paint. Try their website www.technikote.com

Technikote
63 Seabring St.
Brooklyn, New York 11231
Phone: (718) 624-6429
Fax: (718) 624-0129

[ 10-09-2003, 06:31 PM: Message edited by: Ken Layton ]

Posted by John Pytlak (Member # 331) on 10-09-2003, 07:44 AM:

The Technikote site is currently "under construction".