Projection: How to spread the magic
Despite being the oldest of all AV technologies, projection is often not properly understood.
Finding the right model means carefully matching the technology to the space and selecting the right accessories. Fortunately there are tools and standards to help, says Paul Bray.
Projectors are the comeback kids of the AV world. Once written off as virtually obsolete, the latest solid-state technologies have liberated them from darkened rooms and given them the ability to compete with flat panels and video walls on their home turf, with a combination of flexibility, reach and cost per square metre that is virtually unbeatable.
No other technology can instantly transform the side of a gas-holder into a hanging garden, or paint walls, ceilings and floors with a kaleidoscope of priceless artworks. And in lecture halls, museum galleries and retail stores, classrooms, conference rooms and Microsoft Teams Rooms, projectors are often cheaper and more energy-efficient than the flat panel or video wall alternative.
So how do you choose? By looking into space – or rather, the space. Any technology needs to be appropriate to where it is used. But the unique nature of projection means it is particularly important that the technology and the space are a perfect match.
Some considerations are practical. “What’s the space being used for, how high is the ceiling, how much room is there when you walk in, might people knock the projector or walk in front of it, and where can you actually put it?” asks Bas van Tuijl, technical development manager at integrator, Hutchison Technologies.
Measure ambient light
You will need to carefully measure the ambient light levels (ie. how bright the space is) to know what the projector will have to compete with, and consider the kind of content to be displayed. Will this be large-scale pictures or detailed text, moving or still, is faithful colour reproduction important (eg. for corporate branding)? Only then can you start to specify the size, quality and brightness of the projected image.
“The process of specifying a projector is widely misunderstood,” says Greg Jeffreys, director of Visual Displays. “The viewer looks at the image, the reflected light, not the projector. So stating that a projector should have 5,000 lumens or 10,000 lumens of brightness is meaningless unless a rigorous process using standards-based calculators is employed.”
Such standards have been produced by industry body, AVIXA and designed as a straightforward calculating tool for integrators, consultants and even end users. “The process flow is first, select the image size using the AVIXA DISCAS standard, and secondly, select the required contrast ratio using the AVIXA ISCR standard. Third select the screen surface suitable for the application. Then you can calculate the projector lumens,” says Jeffreys.
“When used properly, DISCAS often helps users to understand that they need a much larger image than they assumed,” he adds. “This is actually a core advantage of projection, as it’s infinitely scalable in size, resolution and aspect ratio, meaning that, having made the decision to use it, you can specify exactly what each space needs.”
Manufacturers also produce handy calculators. “We have specialised software tools to simulate the whole projection setup, giving a complete overview of the optical parameters, including pixel density, contrast and brightness,” says Koen Van Belle, segment marketing specialist for immersive experiences at Barco.
Inspecting the actual space
There is no substitute for inspecting the actual space before ordering any kit. “I recently visited a new leisure centre with a badminton court and hall that’s also used as a theatre,” recalls Danielle Williams, commercial manager at AVM. “Nothing could hang below 7.5m unless it was removable, so the screen had to be on a winch to lift it right into the ceiling. In use, every time we sorted the keystone, someone walked by and the screen swayed. Had a site inspection taken place, we could have specified a screen with black borders to help mitigate this.”
Solid-state light sources have largely replaced old-style incandescent bulbs. They use less energy, produce better colours, and last far longer – 20,000 hours is the figure manufacturers usually quote. Entry-level projectors generally use an LED light source, while bigger, brighter models are laser-based. There is also a choice between one- and three-chip technologies, or 1DLP and 3DLP.
1DLP laser projectors range in brightness from 7,600 to 23,650 lumens, and can be employed in high-use applications such as museums and conference rooms, says Joel St-Denis, director of product management at Christie.
When displayed, digital images are broken down into three primary colours: red, green and blue (RGB). While 1DLP technology has to project each colour in turn via its single chip (so quickly that the human eye perceives them as a single image), 3DLP has a chip for each colour and projects them simultaneously. The result is a superior quality image, with better contrast and truer colours.
“Only RGB pure laser projectors can reproduce colour approaching the full Rec. 2020 colour space, reproducing true-to-life and on-brand colours,” says St-Denis. They deliver brightness up to 50,000 lumens, suitable for applications such as live events and themed attractions, even outdoors.
The brightness and resolution of the image can be further increased by dividing it between multiple projectors. “This uses edge blending technology, often built into projectors and supported by a similar white point,” says Gerd Kaiser, senior product manager at Sharp NEC Display Solutions. “Several projectors can then create one large picture with excellent colour uniformity. Edge blended projectors have to be readjusted from time to time, which can be done manually or automatically.”
Alternatively, two or more projectors can be doubled up, or ‘stacked’, all projecting the same image on to exactly the same place to achieve double or greater brightness. This can actually work out cheaper than buying a single, super-bright behemoth.
“Software now removes the painstaking task of aligning multi-projector arrays and achieving brightness and colour uniformity, taking only minutes instead of the hours if done manually,” says St-Denis. “It can also compensate for less-than-ideal projection backgrounds.”
“Built-in geometric control and morphing capability supports easier mapping on to large buildings or other structures,” adds Kaiser.
A projector’s lens can be as important as the light source. “Projectors for small or medium installations already have a lens installed, while brighter projectors for large venues have optional lenses, which must be selected depending on screen width and distance,” says Kaiser. “Almost all manufacturers have UST (ultra-short throw) lens options, which enable projection of a large picture from a very short distance.”
Specialist lens for projection
Specialist lenses such as fisheyes can enable even more impressive feats of projection, such as immersive domes (see the project feature on Plymouth’s Market Hall on page 36).
For projectors in multi-user areas, such as lecture theatres, van Tuijl recommends a video switcher and a scaler. “If people are coming in with lots of different laptops with different connectors, you need one box that can take VGA, DisplayPort, USB-C, and so on, and with instantaneous switchover between them.”
Total cost of ownership should be an important consideration for buyers, believes Daniela Karakaci, European field marketing manager for Panasonic Connect. “Event organisers, for example, should be looking at projectors that offer a leading number of maintenance-free hours of operation, and feature the ability to monitor the equipment’s status remotely, and receive predictive warnings of potential issues that might cause downtime.”
After the projector itself, the most important component of the system – although often overlooked – is the surface on which the image will be projected. You can project straight on to a wall, but a good quality screen should deliver much higher quality. The higher the reflectiveness, or ‘gain’, the brighter the image will be. High gain screens require a less bright (aka cheaper) projector, but can increase glare and reduce the viewing angle. As a rule of thumb, a darker, less reflective screen will produce higher image quality and contrast, but will require a brighter projector.
Projectors can be heavy beasts, with top-of-the-range, 50,000 lumen models weighing in at around 90kg – that’s like hanging a rugby prop forward on your wall. Flimsy partition walls may not take the weight, and it may be better to attach the projector to the ceiling instead. Fortunately many projectors can be mounted at a variety of angles, giving the maximum flexibility for positioning, and some can site the lens some distance from the actual projector, connected via fibre-optic cable. This also eliminates any obtrusive noise from the projector’s cooling fan.
Don’t skimp on the mountings, advises van Tuijl. “If you have cheap bracketry and a heavy projector, it’s going to wobble – and 1mm of movement in the projector may be 50mm by the time the image reaches the screen. Anything that vibrates can cause this, from the heating and ventilation system to free weights being dropped in a gym upstairs. Then we need to put in an additional framework so we can hang the projector from a different support, or use an anti-vibration coupler to minimise the transmission of vibrations.”
Even if they don’t fall off the wall, projectors can still be hazardous. “Bright projectors have a very high light intensity in front of the lens,” says Kaiser. “So safety rules specify the distance in front of the lens within which no-one should be while the projector is operating. This depends on the brightness and the lens used, and is defined in the user manual as HD (hazard distance).”
Exterior mounting can bring further challenges, adds Kaiser. “A waterproof cabinet is necessary for outdoor usage, and this will need to be air-conditioned to manage summer temperatures.”
Although solid-state light sources have removed the need to keep changing failed lamp bulbs, projectors still need some maintenance to keep them on top form. “This largely depends on the ambient conditions,” says Van Belle. “If there’s a lot of dust, the lenses and air inlets will need to be cleaned regularly. If the system is in a blended setup, any image drift due to rigging flex will need to be monitored and corrected.”
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Posted: 2nd May 2023