Film-Tech Forum ARCHIVE: Drive-in Cinema Screens

This is topic Drive-in Cinema Screens in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Peter Sheridan (Member # 901) on 07-01-2001, 09:49 AM:

Dear All
I am interested in discussing materials used in building Drive-in Cinema screens. The screens at my Cinema chain in Sydney Australia are of 2 types, Cement surfaced or Ripple steel sufaced. Their average size is 100ft by 50ft. The cement surface produces great results in all but extreme weather conditions but the the ripple (corrugated) steel produces different results from location to location.
On some steel screens a shiny checkerboard pattern appears on heavy dew nights but not on others. During rain, again the steel surfaces produce different results some producing wet shiny and very annoying patterns while others show no effect at all. Is it the paint, surface, or maybe the frame?. What can we do to fix this problem. It has always been a mystery to us and I hope someone can shed some light.

Peter Sheridan

Posted by Stan Gunn (Member # 554) on 07-01-2001, 10:12 AM:

Hi Peter.
Your problems are caused by the ripple in the screen surface,a simular material was used in the old Metro twin here in clayton Melb paddock 2 it was also a disaster causing all kinds of strange effects.

regards.
Stan Gunn

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ALL PARTS FOR VICTOR AND KALART VICTOR 16MM PROJECTORS.
SERVICE TO 35 AND 16MM
PROJECTION EQUIPMENT.

Posted by Peter Sheridan (Member # 901) on 07-01-2001, 10:33 AM:

Thanks Stan.
It seems a rather strange material to use for a screen in the first place and I am still wondering where the idea came from. The key is reflected light as the effects become less and less as the angle of vision to the screen gets flatter. (i.e cars closer to the screen see less reflection) The steel screen at Bass Hill drive-in has a very small area painted with test paint and seems to suffer less in that small area, but of course this is still not conclusive.

Thanks again for your reply

Posted by Stan Gunn (Member # 554) on 07-01-2001, 12:11 PM:

Hi Peter
The main idea behind it was I understand to give a wider spread of light in the larger and wider drive ins. It was a failure,
the best is still the flat surface screen.
regards stan.

------------------
ALL PARTS FOR VICTOR AND KALART VICTOR 16MM PROJECTORS.
SERVICE TO 35 AND 16MM
PROJECTION EQUIPMENT.

Posted by John Pytlak (Member # 331) on 07-01-2001, 01:09 PM:

When a drive-in screen gets wet, it usually becomes more specular (mirror-like) in its reflection. So the corregated surface reflects light uniformly when dry, but very directionally when wet, accentuating the rippled surface.

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
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Posted by John Wilson (Member # 269) on 07-02-2001, 03:44 AM:

Hi Peter

Welcome to the forum! How've you been?

On wet nights we used to advise the patrons to park off-centre to avoid the white spot on the screen. The ripple effect was also very prominent in the early mornings as the cold weather and the dew were affecting the screen.

I can't recall what it was they used to coat them, but every time they were painted they said it would solve most problems...but we never saw too much difference...just a brighter picture, which was always nice.

If you want to take a look at my old haunts, then Click Here and then Click Here Too!

Come on out to the Ritz soon and take a look at Film Guard in action. It'll knock your socks off.

John

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"If you think THIS is fantastic...wait until you see the full effect with the HIMP!"
- Chief Inspector Clouseau.

Posted by Peter Berrett (Member # 672) on 07-02-2001, 03:59 AM:

Hi Peter

Funny that this subject should come up now. Last night I was at Coburg Drive-in here in Melbourne (watching Swordfish) on Coburg's big screen 1.

I noticed something different that night. I noticed what appeared to be vertical ripples running through the screen. The effect was somewhat like having a dusty tv screen too as soem bits of the screen shone brighter than others. It is quite annoying. Noticeably that night there was a bit of fog about.

I haven't looked closely but I guess the screen is made of corrugated iron with the ripples running vertically. It seems to confirm comments made earlier by others.

I recommend you go with a flat screen.

cheers Peter

Posted by Tom Hutchinson (Member # 876) on 07-02-2001, 04:23 PM:

It is my understanding that the corrogated steel gives the projected light beam essentially 3 different surfaces to light, at 3 different angles...because the projector is at a right angle to the screen.

Another source of light, say the moon, or field lights, or parking lot lights from the gas station next door, will likely only hit one or at most two of those surfaces, thus making the effect of the stray light less noticeable.

In this territory, the best screens were corrogated steel; the worst were plywood. They are pretty well all gone now.

Tom

Posted by David Kilderry (Member # 142) on 07-03-2001, 06:32 AM:

Early drive-in screens were either cement block or marine ply, both flat surfaces. As John and others correctly point out, when these became wet due to rain or moisture in the air, they became more specular. In other words they produced a hot spot. The reflectivness or gain of the paint on the surface would accentuate this.

Corrugated sheet screens began to appear in an attempt to deflect this annoying relection in a number of angles and not all back toward the centre of the field. Some were successful, others not.

From my experience, I have found that a flat zinc-alum panel is the best drive-in screen material for all weather conditions. Coburg triple has one corrugated screen and two flat panel screens, the flat panel screen is certainly the best when wet compared to the other and has the same light with the same lamphouse and lens setup as the corrugated screen.

I have noticed the annoying reflection at both Bass Hill and Blacktown as Peter states. I would suggest Wattyl Solarguard paint. This was found to be the best all round paint available. It provides good reflective qualities without annoying hot spots.

The big drive-in circuits once had a great deal of accumulated information on topics such as these. Unfortunately much of this research and knowledge is lost or not available to the independant drive-in operator. The company I work for once had 40 drive-ins and thankfully most of this information has been retained and is still put to good use.

I'll say it again, the single most important tool when considering any aspect of theatre screen light is the cine spot meter. It amazes me how many large circuits still do not own one. You are chasing shadows and guessing in the dark without one. When a drive-in in particular needs every ounce of light available, a quality meter is invaluable.

David Kilderry

Posted by Peter Sheridan (Member # 901) on 07-03-2001, 06:59 AM:

Hi David, John and all.

Nice to see so much experience here. Should have found this forum a lot earlier.

The answers you all supplied certainly help for my info and I agree with you David, but so much has been lost to time. I suppose we have to be thankful that we still have some Drive-ins still in operation and by and large still maintained very well.

Currently the Blacktown location is about to receive a complete ground resurfacing. The screen at Bass Hill has been cleaned and a anti bird guard applied to the top to keep it white for as long as possible.

Getting back to screen materials, I think of all the screens I have seen from both an operators and a patrons point of view, the cement is the best. I have seen blinding storms drenching the screen yet it still seems to hold up well. The tinny starts reflecting if you breath on it the wrong way One metal screen is not too bad but seems to be rather over engineered. I was theorising that maybe the massive frame works as a kind of temperature ballast in cold weather. Thanks too all for the info. Now all we have to do is get more light onto the screen, or will this accentuate the problem?

Peter

Posted by John Pytlak (Member # 331) on 07-03-2001, 09:01 AM:

David Kilderry said: "I'll say it again, the single most important tool when considering any aspect of theatre screen light is the cine spot meter. It amazes me how many large circuits still do not own one. You are chasing shadows and guessing in the dark without one. When a drive-in in particular needs every ounce of light available, a quality meter is invaluable."

Wonderful advice. Kodak has published information on screen luminance meters:
Screen Luminance Meters

Here are some links to various meters:
Minolta LS-100
USL PSA-200
Spectra-Cine Meter

Again, the cost of a good meter seems high, but the meter can be shared by many screens, and should last indefinitely. You wouldn't think of aligning a sound system without the proper equipment, why not have the right tool to assure proper screen luminance?