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Panasonic’s DLE030 lens has a throw ratio of 0.38-1, which the company says obviates the need for mirror systems and metal frames

incredibly important part of any projector,” he confirms. “It ensures that focus across the entire image is consistent and ensures no distortion at minimum or maximum zoom levels.”

“If I had to choose between the lens and the image processing as being the most significant contributor to image quality,” says Greg Jeffreys, managing director of projection solutions specialist Paradigm AV, “it would be the lens.”

NEW FUNCTIONALITY Image quality, however, isn’t the only parameter in projector lens design as manufacturers look to drive sales in new applications. Here, the functionality of the lens makes a significant contribution – but is this functionality at the cost of image quality? Are there trade-offs and compromises to be made? Wadsworth again: “There

will always be a compromise between the theoretical maximum performance of a projection lens and the competing specifications demanded of the lens,” he believes. “Usually, for a given lens design, the increase in one specification parameter will come at the expense of other parameters unless the original design is modified by increasing its capability with more design parameters – such as additional lenses. However, the normal mode of lens design will be to design the lens to a given specification. The specification will also include cost, so that can be treated as another design parameter which competes against the others.” Gerd Kaiser, product line

manager for large-venue projectors at NEC Display Solutions, sees things similarly. “Because of optical limitations, high flexibility in a lens will always involve a compromise with best

achievable quality,” he says. “Projector manufacturers have to find the right balance between lens features and good optical performance. Providing just features makes no sense if the quality is not acceptable for customers.” Kulessa warms to the theme. “Every lens that features zoom and shift will require a larger glass body,” he says. “To make best picture quality and a crisp and perfectly focused image needs carefully engineered and precisely manufactured and shaped lenses. If you put the two together, it means increasing the cost. Of course, there is value in a large lens shift, but what is its real value if it comes at the price of picture distortion and pincushion effects? We always have the best picture quality in mind, which is why Panasonic lenses are probably not the cheapest, but always assure best picture quality and installation flexibility.” “We have always prided

ourselves at Barco in offering installation flexibility and allowing offsets and zooms that sometimes others do not have,” adds Marples. “We can usually achieve this without reducing image quality, but it does sometimes mean very expensive lens designs. Also, each lens within a range – on the same projector – will have slightly different transmission values, which means that maximum light output is usually achieved through one or two lenses only, while the others may transmit less light due to the extra glass in the path.” Inevitably, lenses are designed with a specific target market in mind – and in some of those markets, price may be a more important consideration than absolute image quality.

FLEXIBILITY IS KEY “Every installation is different, so flexibility and functionality are the key factors in lens AV SHOW STRETCHES LENS CAPABILITIES TO THE LIMIT

Originally a stone quarry, the Carrieres in Les Baux-de- Provence, France, has been transformed into a backdrop for a stunning audiovisual show, where images are projected on to the walls and the floor.

Multiple surfaces are used in the show to give a sense of depth, while spectators are immersed in the projected images. The walls, ceiling and even the ground are completely covered, becoming

design to cater for all scenarios and provide greater installation opportunities,” Halls notes. “This does not always equate to reduced image quality.” “Optoma’s new special effects short throw lens provides an affordable very short throw solution specifically tailored for video and moving images,” he continues. “Its throw ratio is comparable to similar lenses used in classroom environments for education.” Jeffreys sums up the situation. “Yes,” he says, “there are quality compromises, but in practice, the actual ability to have these flexibilities outweighs the negatives.” The development that

has pretty much taken the market by storm has been short throw and,

a vast carpet of images. This huge space required the Optoma projectors, and the lenses used within them, to be extremely flexible. As a result, a variety of projectors and lens were needed, some installed to project vertically. The cavern is more than 6m high in places so the installation required long- throw lenses for images to reach the roof, while short- throw lenses were used within small nooks.

eventually, ultra-short throw (UST) lenses. “Short throw lenses are becoming massively popular,” proclaims Kulessa. “In fixed installation applications – in museums and public display, for example – we see an uplift in the use of projectors in general and very often, whether rear or front projection, from a relatively short distance.” “A year ago, Panasonic launched what we believe is another breakthrough innovation,” he goes on. “With the ET-DLE030 lens, we can offer an exchangeable ultra-short throw lens for high-brightness projectors

Lens shift and off-axis

projection were essential to project around obstacles formed by the irregular space. Spectators are totally immersed in the images projected onto all the surfaces of the rock. Work by Gaugin and Van Gogh currently feature in one film, while themes of nature are shown in another film. The subjects of the films are changed each year.

that allows a throw ratio of 0.38:1. This opens new applications for projectors and lets installers and system integrators do away with massive mirror systems and metal frames when they’re trying to configure space-efficient projection solutions.”

“Optoma has seen a

greater demand for short throw lenses with off-axis capabilities and projectors which have lens shift functionality for installations that have space constraints and/or need rear projection onto large screens,” adds Halls. “Having lens shift for short throw lenses is unusual because the lenses themselves are often fairly wide in size which leaves very little room to physically shift the lens. Because Optoma

In common with many manufacturers, Digital Projection offers a broad range of lenses to support a wide variety of potential applications

June 2014 29


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