Choosing a Digital Projector Choosing a Digital ProjectorThere are two mainstream competing technologies; DLP and LCD. DLP has the benefit of excellent contrast, which produces really good blacks if the room is dark enough. On the downside, some people can see rainbow colours when their eyes scan the projected image. LCD colours are arguably more naturalistic and accurate and historically the projectors have been cheaper, but LCD can produce a visible grid on the screen. Both technologies can produce stunning images and developments are continually improving the results that they can achieve so there is no clear winner and both have their advocates. Over time other emerging technologies such as LCOS may join the mainstream bringing their own price/performance benefits.
Minimum resolution should be XGA (1024x768 pixels). Just as with digital cameras there will be a gradual increase in resolution over time but although XGA amounts to less than one megapixel, that is sufficient to produce images of high quality and detail, because of the brightness, contrast and viewing distances involved. Higher resolution than XGA is an advantage if the budget is sufficient. SXGA at 1280x1024 puts 60% more pixels on the screen than XGA. Of course, you need a laptop or computer capable of displaying at the chosen resolution, and older equipment may not handle SXGA.
Projectors are mostly either 4:3 or widescreen 16:9 although SXGA projectors are 5:4. Compact digital cameras are usually 4:3 but digital SLRs follow the traditional 35mm film format of 3:2. An exact match between all images and the projector is therefore impossible but the main recommendation would be to avoid widescreen 16:9 projectors because images in portrait format would be severely cramped and disadvantaged in terms of on-screen size.
This depends upon the size of the room, blackout conditions, screen type and personal preferences but a projector in the range 1000 to 2000 lumens is likely to be a safe choice. LCD projectors tend to be brighter than DLP.
Most projectors have a zoom lens to make fine adjustments to the image size without moving the projector. These can be quite limited in range and powered or unpowered. Many projectors are designed for office use and have a short-throw wide-angle lens. This will result in the projector being located more closely to the screen than has typically been the case with traditional 35mm projectors. Digital projectors are available with interchangeable lenses but these are normally prohibitively expensive.
It may be advantageous to have features such as back-projection (eg for exhibitions). A quiet fan is also a benefit. Although some form of keystone correction is usually built-in, it is preferable to position the projector correctly rather than use this feature as it has a detrimental impact on image quality. Portability is also likely to be important unless the projector can be securely stored nearby to the clubroom.
Highly reflective or directional (eg beaded) screens may not be suitable for a digital projector and a larger room. In addition to uneven illumination, a beaded screen can produce moire patterns with some digital projectors. A grey or non-beaded white screen should produce acceptable results but this could be a good opportunity to consider replacing an old screen with a modern one.
It is essential to have the projector/computer combination professionally colour-profiled to ensure that they deliver accurate colours. In practice, this requires you to use the same computer and projector every time as the profile actually resides on the computer.
Other factors to consider in a procurement exercise are; computer or laptop (ideally with matching screen format and resolution), competition software, other software (eg Photoshop & Anti-Virus), colour profiling, protective cases, projector stand and screen. You may also find that the equipment generates a resurgence of interest in audio-visuals in which case you may need to purchase suitable powered speakers. As the life of the projector bulb is measured in thousands or hours, you may consider it unnecessary to purchase an extraordinarily expensive spare bulb as the life of the projector is likely to exceed the life of the bulb and gas-discharge lamps do not usually fail prematurely.
Whichever projector and computer you decide upon, they will be obsolete within five years. In addition, the equipment will need require periodic maintenance and software upgrades so it is strongly recommended that funding is put aside annually for maintenance and eventual replacement.
Further information on choosing a projector is published by ProjectorPoint.
For information about running digital competitions, see Running Digital Projected Image competitions.
This document was produced in January 2006 by Steve Brabner and Phil Stapleton for the Chilterns Association of Camera Clubs.