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Voyage to the Outer Planets (1973)
Garden Isle (1973)
Standing Up Country (1973)
Cosmos (1974)
Viva Baja (1975)
Rivers of North America (1976)
Ocean (1977)
Alfa (1978)
Genesis (1979)
Atmos (Storm) (1980)
The Eruption of Mount St. Helens (1980)
Library of Astronomical Phenomena (1980)
The Great Barrier Reef (1980)

In production:

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My question is concerning the curved screens. All of our frames are curved but only a mild one. I'm assuming this had something to do with the old 20 pound Super Panatar prism anamorphics that we used to employ. Nowdays we are using Schneiders and the majority of our screens are average 15 x 35 feet. Most auditoriums seat 400 - 500
with a couple theaters twice as large.

About six years ago we began being issued silver screens to replace our matte whites. We get good contrast and brightness but that is only for the audience in the middle seats. Our auditoriums are multi use facilities so the seat rows go quite far off of center. Also being multi use these silver screens are prone to gathering handprints, etc.

At ShoWest this last March the Harkness Hall folks said we should not be using silver at all but rather Perlux or matte white. I wonder what the group would have to say about this. I have read through all the earlier postings and can find nothing to disagree with as you all have good points indeed.

Would Perlux give the best features of both matte white and silver?

Depending on the curve of your screen, either a matte-white or a perlux (if using Harkness) would indeed be appropriate. If the curve' radius is on the order of the projection distance, then matte-white would be my preference...as the curve increases (shorter radius) then the pearl screen will peform best. To really get the right screen though, one HAS to match up screen-gain with the geometry of the projection and auditorium. People that just pick a screen gain and radius willy nilly, don't know what they are doing.

Steve

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SMPTE Recommended Practice RP 95 specifies "Installation of Gain Screens".

The optimal way to determine the proper curve is by ray tracing. The idea is to curve a gain screen such that the projected light is reflected back to the center of the prime seating area.

Very high gain "silver" screens are VERY directional, and as you note, sensitive to handprints, showing seams, etc. Their primary application is polarized 3D projection, which requires a screen that maintains polarization of the reflected light.

For moderate (15 x 35 foot) sized screens, a matte or slight gain surface is the best choice, since getting enough light is usually not an issue.

Here are some links to information:
http://www.bksts.demon.co.uk/articles/jul97.htm
http://www.harknesshall.com/data1.htm
http://www.kodak.com/US/en/motion/newsletters/reel/fall97/screen.shtml
http://www.schneideroptics.com/software/theatre_design_pro/
http://www.schneideroptics.com/info/white_papers/cinema_projection_distortion.pdf

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

Proper installation of a Harkness screen is imperitive for proper performance of the surface and few people are aware of how this should be done. The top of the screen should be installed with either lacing cord loops all the same size, or black cable ties. The bottom of the screen is then stretched about ten to twelve inches, or to make the top and bottom gap even. Use standard lacing procedures on the bottom but go back and forth a couple of times to stretch it down that much. The sides can be sprung or laced in, what ever you prefer. On curved frames pay close attention to the center of the screen to be sure that it does not belly out from being tensioned too tight on the sides. When the screen is tensioned ten inches to a foot, the seams and any slight wrinkles literally vanish completely and the surface looks to be seamless.
Mark @ GTS

Here is a tidbit about how directive silver is. As I stated, we use these auditoriums during the day for other functions besides movies. A commander will assemble the troops for some briefing and use his slide projector to illustrate some topic. When we first switched over to silver the first complaint was "what have you done to the screen?" "We can't see our slides anymore." Well, since their wimpy projectors were setup at chair level all the light was now being reflected up into the border curtains at the top of the stage. If I went into our booth I could see a beautiful bright image but the viewers in the seats would only see a low contrast washed out picture. When I change to Perlux these folks should get most of their picture back.

Thanks everyone for your thoughts on this issue. Have a nice Thanksgiving.