posted 08-14-2004 07:21 AM                       

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Contrast Killer 5: Poor Ports
The projection port is just as important as the lens in delivering high-quality
images. Plain window glass should not be used. Only optical quality glass with
anti-reflection coatings should be used. Port glass should never be installed
perpendicular to the projection beam, to avoid reflecting light back into the
projector lens. Likewise, if two panes of port glass are needed for sound
isolation, care should be taken to avoid internal re-reflection. Soundproof,
angled port glass frames are available from several vendors. Port glass should
be absolutely clean and scratch-free. As with the projection lenses, loose dust
should be gently brushed away with a camels-hair lens brush, and liquid lens
cleaner and lens tissue used for cleaning any haze. Ideally, the projected
image should be almost invisible on the port glass, with no detectable
scratches or haze.

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Regardless of the wall structure, projector noise will escape through any single sheet of projection glass. port glasses should be angled to reduce lateral reflections; as a worst case example, internal reflections from a single port glass set at 900 to the line from lens to screen will result in numerous reflections leading to a soft screen image apparently out-of-focus. A good result will be a front glass set at perhaps 70 forward from the lens angle, and a rear (auditorium side) glass set at 150 backwards.

Care should be taken over the quality of glass used, and optimum projection requires coating to further avoid internal reflections. (3)

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Our port window glass is called Water White. The transmission rate is between 98% and 99%. The glass transmits 99% < 3mm thick, 98% > 6mm thick of the visible spectrum. For more details on the specs see our Water White glass page. Standard port window glass thickenss is 6mm. We have 8mm and 10mm available as well, with 12mm available in the winter of 2001.
This glass is ideal for use in theater projection rooms, in what are called port windows. The dual A/R Coating increases the transmissivity to provide true color through the glass. This is the highest clarity port window glass, with no coloration. The port glass in the projection room is nearly invisible.

Regular glass absorbs the colors and brightness of projected light, thus dulling the screen image. Optical Coatings' specially coated glass transmits more light onto the projection screen. Movies are seen the way the Director and Cinematographer intended - with brighter, truer colors.

Our high transmission, two-sided antireflective coated clear glass is suitable for use in motion picture projection room construction. Our glass is especially suitable for multiple projectors, such as those in IMAX theaters, where every bit of light transmission is critical.

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By the same token that it is imperative to use only the finest objective lens in connection with the SUPER PANATAR, it is quite important that only the best grade of glass be used in the projection port. The glass should be water-white, optically flawless, coated, and should be treated with the same care as a lens. If these precautions are not taken, the port glass can introduce loss of definition, loss of light transmission, and a detrimental change of color in the projected image.

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Water white, low iron, ultra clear glass transmits 98% to 99% of light, and is anti-glare and ant-reflective coated. This glass is preferred for all theater technology, and is necessary for digital equipment. Water White Glass allows lower intensity light to be passed through the port. Used as a theater glass, our water white glass outperforms other ultra clear products. We use a process that insures defect free glass.
American Computer Optic's OptiClear Water White Glass is the port window glass of choice for Christie Digital Labs and THX Labs. Thicknesses are available in 3mm, 6mm and 10mm. Water White Glass under 3mm thick transmits 99% of visible light, while over 3mm thick transmits 98% of visible light. Sheets are available up to 6ft X 8ft. Use our contact form to request a quote. Please include size and thickness specifications.

Water white glass is available as tempered product. Hydrophobic coating is also available to repel dust, dirt, water and oil build-up.

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posted 08-15-2004 09:47 AM                    

quote: Bill Langfield

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They just cared about how many up-sized popcorn/cokes they could sell.

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