In The Dark Without Data
Indoor movie theaters offer moviegoers an extraordinary viewing experience. Movie studio standards are high, and every feature that makes a movie house magical cannot be moved outdoors.
Thankfully, top-quality projection surfaces are available for outdoor movies.
Across the landscape of projection surfaces, several are stellar. Many however are compromised by materials and mounting methods that fall far short of a true theatrical viewing experience.
Start with the surface itself: ask to see a datasheet! Without data you’ll be in the dark about details audiences are sure to notice.
Something to Gain
Gain is the ratio of projector output reflected back from a screen surface, and 1.0 equals 100% of what bounces back from an industry-standard reference board.
Gain is measured from where the screen appears brightest, typically the horizontal center of the screen in line with the projector. This position is called Peak Gain at Zero Degree Viewing Axis, and moving along an arc one way or the other diminishes brightness. Where it dims by 50% is the Half Gain Viewing Angle, although 20% loss is the common cutoff for acceptable viewing.
A screen with 0.8 gain will reflect 80% of a projector’s brightness, and a 1.2 gain screen will increase perceived brightness to 120% of projector output at the center axis.
As a rule of thumb, expect a more narrow cone of acceptable brightness from high-gain screens and a wider seating area from low-gain screens
Independent of the optimal viewing cone, screen gain can be traded for improved contrast, but lower gain can also translate to reduced luminance at all angles.
Viewing Axis
A luminance chart like the one above is required reading because it approximates which side seat positions will be cut off by off-axis falloff compared to sitting on the center-aisle.
True Color?
A color reflection chart provides another performance preview. Everything a projector beams to the screen does not bounce back to the audience, and color distortion is an unpleasant flaw at every price point. Reject any screen which fails to deliver a smooth and relatively flat response (with no spikes or dips) across the color range.
Beyond The Specs
A great projection surface is a significant investment, and if marketing hype or missing specs stand in the way of making an informed decision then post your questions to the Outdoor Movie Business Community.
Names can be misleading, and prices are all over the map. Do not automatically trust products called “cinema fabric” or “theatrical screen surface”.
To help narrow the field, here are features a ‘smooth operator’ wants to have in an inflatable movie screen projection surface, along with pitfalls to avoid.
Attachment Method
How a projection surface is attached to the surrounding frame is critical to its appearance and performance. Screen-mounting categories include:
Zippers, clips or snaps
- Prone to failure: dirt, mud, grass and insects accumulate in zipper teeth and clasp hardware
- Creases and puckers are difficult to avoid
- Surface tension cannot be adjusted
Hook and eye (Velcro type)
- An economical sweet spot
- Easy to remove for cleaning or storage
- Adjustable border helps flatten the projection area
Elastic Screen Ties (Bungees)
- Applies tension evenly
- Responds favorably to temperature changes
- Transfers wind loads to the movie screen frame
- Long the tradition in the movie exhibition business
Projection Surface Materials
Textiles
Fabric screen surfaces allow significant light to pass through, which reduces screen gain and increases the level of projector output required to reflect an acceptably bright image.
Textured fabrics also undermine image resolution and detail perception, often annoying audiences (and stakeholders) at close and middle distances.
Machine washing fabrics, with or without seams, can stretch or pucker the projection surface at the edges.
Laminated PVC
Projection surfaces made from laminated PVC are superior to textile options for a number of reasons:
- Optimal contrast, color accuracy, brightness and gain
- Weight typically translates to wind resistance, although protection against puncture or tears is not a function of thickness
- Resists staining much better than textiles. Mud and insects wash off PVC with a sponge and mild detergent. Fabrics have to be removed to launder or dry clean.
Plastics stretch in high temperatures, so verify operating range with the manufacturer or reseller.
Front/Rear Projection
Be skeptical of claims that one screen surface performs ‘just fine’ for both front and rear projection.
Front surfaces reflect light, rear surfaces diffuse light and unfavorable compromises are inevitable.
Buy the best front projection surface your budget affords, try it for rear projection and accept its shortcomings. Plan to purchase a separate rear projection surface. Also keep in mind that many entry-level projectors have a fixed zoom lens incapable of short-throw distances.
Backing Bonus
Projection surfaces with black backing prevent rear ambient light from dimming front-projected images. A removable backing is a versatile bonus.
FAQs
What is movie screen gain?
Gain is the ratio of projector output reflected back from a screen surface, and 1.0 equals 100% of what bounces back from an industry-standard reference board.
Gain is measured from where the screen appears brightest, almost always at the center of the screen in line with the projector. This position is called Peak Gain at Zero Degree Viewing Axis, and moving along an arc one way or the other diminishes brightness. Where it dims by 50% is known as the Half Gain Viewing Angle, although 20% loss is the common cutoff for acceptable viewing.
A screen with 0.8 gain will reflect 80% of a projector’s brightness, and a 1.2 gain screen will increase perceived brightness to 120% of projector output at the center axis.
How is the projection surface attached to an inflatable movie screen frame?
Elastic Screen Ties (Bungees): They apply tension evenly, respond favorably to temperature changes, efficiently transfer wind loads to the movie screen frame, and are long the tradition in the movie exhibition business
Hook and Eye (velcro type): An economical sweet spot, easy to remove for cleaning or storage, and a stretch border can be added to flex and flatten the projection area
Zippers: Prone to failure because dirt, mud, grass and insects accumulate in zipper teeth, plus creases and puckers are difficult to avoid because surface tension cannot be adjusted
