Buyer’s guide to short-throw projectors
Posted on 16 Jun 2012 at 17:16
More important than the technology are specifications, and there are three key areas. Resolution determines image sharpness, and most education-focused projectors offer a XGA (1,024 x 768) or WXGA (1,280 x 800) native resolution. The latter has a widescreen aspect ratio (16:10) and is more suitable for interactive whiteboards. Brightness is measured in lumens: the brighter the image, the easier it is to see in a well-lit classroom. The best projectors offer at least 2,500 lumens brightness. The contrast ratio determines how light or dark images appear; whether an object looks a deep black or a washed-out grey. As a rule of thumb, the higher the contrast ratio, the better the image quality.
Connectivity is important because it will determine the number and type of devices that can be connected to your projector. If the projector is destined for a fixed location (such as a ceiling mount), it’s important that you don’t have to keep plugging in and unplugging devices. Virtually all projectors offer D-SUB in and out, S-Video and composite video as standard, but if you want to use a Blu-ray player with your projector, say, then an HDMI port is useful. Some projectors also include USB ports for displaying images stored on flash drives.
Short-throw projectors command a price premium, although prices are falling and some models are now around £400. But while price is important, so are running costs. LCD projectors use dust filters that must be regularly cleaned, and eventually replaced. All projectors will need their lamp replacing at some time, and it pays to compare the stated lamp life. Bear in mind, though, that manufacturers’ lifetime ratings are often shorter in the real world. Eco and economy modes can extend lamp life, but check how much these modes affect image brightness.
All projectors use a fan, and you should ensure that the noise level isn’t intrusive. Also look for security features such as password and PIN protection – and use them! Finally, check what warranty comes with your projector and what it covers. Some manufacturers offer extended warranties for schools, and these can bring extra peace of mind.
Getting 3D ready
A growing number of projectors now advertise themselves as “3D Ready”, but what does this actually mean? All it guarantees is that the projector will accept a 3D signal in at least one of the four most widely used formats – frame sequential, checkerboard, side by side or frame packing – and display it, provided you have the right equipment. The equipment needed will vary from brand to brand, but in most cases you’ll be looking at a 3D adapter unit, which synchronises the left- and right-eye frames being projected with the left- and right-eye shutters in the 3D glasses, or an adapter – such as Nvidia’s 3D Vision system – that plugs into your PC. As you’ll also need to buy a number of compatible 3D glasses, often costing upwards of £50 each, getting into 3D can be an expensive business.
The other part of the puzzle is 3D content. This is coming online, and anyone who attended BETT this year couldn’t help but be impressed by the quality of 3D anatomical models and 3D maps being exhibited, all visualising subjects in a way that 2D graphics can’t easily match. Seeing a diagram of the human lung is one thing, but watching the bronchioles swell and shrink in 3D as your view moves through the body is quite another.
Companies such as Designmate, Amazing Interactives, Xpand and Cyber-Anatomy are pioneering here, but there’s a definite bias towards science over other areas of the curriculum, and it’s questionable whether there’s enough material out there yet to justify a move into 3D now. However, early studies look promising, with teachers in pilot projects praising the impact that 3D has on students, and the way it seems to get them talking and help them retain knowledge. Don’t write off 3D as a gimmick quite yet: it could one day become an essential classroom tool.
Author: George Cole
Installation Issues - Short-thow Advantage
I've come across numerous cases where a long throw projector has been installed directly on to the ceiling of the room instead of being 'normal' to the screen (presumably to save money or 'hide' the projector). Trapezoidal correction of the projected image has then to be used to match the screen/whiteboardg giving a different number of pixels for the top and bottem rows of the image on the screen.
The resulting image has a very low effective resolution for text due to the vertical lines crossing pixels.
A short-throw projector would eliminate this problem as it uses a special lens to optically make the correction.
By jcaiken on 2 Jan 2013
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