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Determining the best LED-screen configuration for your project or rental inventory.
 Two on-stage image magnification (IMAG) LED panels create mirror images of performer Dave Matthews. |
IF YOU ARE A PRODUCTION DESIGNER looking to incorporate LED displays into your event for the first time or an A/V rental company considering stocking LED screens, you now have a wider choice of LED products to choose from than ever before. The following are the major factors to consider in making your decision.
LED's Advantages
LED panels come in an array of shapes, sizes, resolutions, and packaging. Quality has improved recently with screen pixel pitch (the spacing between individual pixels) becoming finer by the year, taking LED into areas where projectors and video-wall cubes once ruled.
LED's generic benefits of low weight, modularity (manufacturers' integral parts are located within each individual panel for ease of assembly and disassembly), very high brightness, and excellent color rendition suit it to the entire spectrum of performance.
In particular, the low weight of LED screens, especially compared to other panels, and not requiring a specific support structure give event producers the option of having LED panels move, track, fly in and out, break apart, and re-form. They can also be flown from a structure, roof, or crane. Computer generated graphics and video, combined with screen movements, can be used to conjure a completely new visual world on stage. All this produces endless creative possibilities for a wide range of applications.
LED screens are capable of displaying image sources from most types of computer data, graphics, recorded video, and live-camera feeds. Panels can be used individually as set elements, combined to form vertical or horizontal strips, or used in the conventional way as a complete giant screen that can use almost any aspect ratio from the standard 4:3 television format to 16:9 widescreen to wherever your imagination takes you. Screens can be assembled in curved shapes. Recently, a horizontally concave LED screen formed the central backdrop for shows by the rock band Oasis, with the stage flanked by conventionally configured flat screens.
With state-of-the-art processing, screens are now capable of reproducing 8,192 shades of each color. This translates into more color combinations and allows a better definition of colors. For instance, whites can be truly white; not white with a reddish tinge to it.
Making the Right Choice
Choosing the right type of screen for your project or rental inventory depends on a number of factors. At the outset, several questions need to be answered to determine the best screen for the job.
Will the screen be used indoors or outdoors? What is the overall size of the screen? What is the primary feed to the display? Will there be image magnification (IMAG)? What will the viewing distance be? How will the screen be deployed: flown or ground supported (a key point for the rigging and staging design)?
The technicalities of screen choice reside partly around screen construction. There are two types of LED panels — conventional, using discrete LEDs, and SMD (Surface Mount Device) panels. Most outdoor screens and some indoor screens are built around discrete LEDs, also known as individually mounted LEDs. A cluster of red, green, and blue diodes is driven together to form a full-color pixel, usually square in shape. These pixels are spaced evenly apart and are measured from center to center for absolute pixel resolution.
Most indoor screens on the market are built using SMD technology — a trend that is now extending to the outdoor market. An SMD pixel consists of red, green, and blue diodes mounted on a chipset, which is then mounted on the driver PC board. The individual diodes are smaller than a pin and are set very close together. The difference is that minimum viewing distance is reduced by 25% from the discrete diode screen with the same resolution.
Indoor use generally requires a screen that is based on SMD technology and has a minimum brightness of 600 nits (a standard unit of luminance — candelas per square meter). This will usually be more than sufficient for corporate and retail applications, but under high ambient-brightness conditions, you may need more punch to compete. Fashion and auto shows are two examples of high-brightness stage lighting that may require a higher LED brightness. Conversely, when your screen may be in a shot on a television show, the requirement will often be for lower brightness levels with lower color temperatures.
For outdoor use, you need at least 2,000 nits for most situations, whereas higher brightness types of up to 5,000 nits cope even better with direct sunlight on the screen. Until recently, only discrete diode screens could achieve that brightness level. (The brightness of LED panels also can be turned down.)
For specific projects, you need to take into account factors such as sight lines, local authority planning requirements (if the installation is to become semi-permanent), vehicular access (trucks carrying the screen, truck-mounted screens, or cranes), cable runs for power and video (accounting for both distance and health and safety requirements), power, suitability of the ground for the location of the screen (check to make sure there are no pipes, shallow drains, caves, or tunnels that may not be able to support heavy loads), and overhead obstructions.
Pixel Resolution/Viewing Distance
Pixel pitch is a factor for both indoor applications where the viewing audience may be fairly close to the screen and outdoor applications. Typical outdoor screens are in the 10mm to 25mm pixel-pitch range. For indoor use, the newer screens have pixel pitches of 10mm or less for close-range viewing.
There are many myths about how to calculate the minimum viewing distance for LED screens. A simple calculation, however, is all that is needed for measuring the distance (see chart on left). The minimum viewing distance is defined as the value that will allow the eyes to see a smooth image. Closer viewing will produce an image with pixels appearing as dots. For a typical 9.5'×12.6' 10mm SMD screen, the color compound distance is 8.2ft. This is the distance that allows the LEDs to mix and form a single color. This is not, however, the minimum viewing distance. For minimum viewing distance, first define what type of LED screen will be used. Will it be a discrete diode screen or SMD? This makes a difference in the calculation.
On the Road
If you are contemplating buying screen panels to add to rental stock, you also need to consider the inevitable maintenance on the road. Touring modern LED panels are rugged and travel in flight cases, but they live longer with proper handling. LEDs have a long life expectancy, and the latest panels, equipped with serial digital-signal interfaces, have more reliable, low-maintenance cabling systems than earlier designs.
Finally, production managers should not cut corners with service and support from both A/V hire companies and manufacturers. Comprehensive support and experience on the road is as important from your screen supplier as it is from your lighting or audio company. For A/V rental companies, good manufacturer/distributor support is equally important.
Alan Barber is West Coast sales manager at Lighthouse Superscreens, Inc. (www.lighthouse-tech.com). He has more than 13 years of experience in the rental and staging market. Email at [email protected].