How Many Screens and Lumens?

There is a very simple way to determine how many screens you need for proper AV playback in the section below:

- Long rooms of 100 - 200 feet work best with one big screen (7.5' x 10' or 9' x 12'). The reason is that people at the back are always bouncing their eyes between the screens if there are two in a long room. Also, even the best-matched projectors aren't always the same color - this won't always be evident with every picture, but it depends on the colors played back (the bulbs aren't exactly the same). Further, if you have to swap a projector with an un-matched projector, good luck matching them! It looks cheap and your meeting will be judged accordingly.

- Wide rooms work best with a stereo screen set-up (two screens) because you have to ensure everybody can see. But, get a matched set of projectors (however, see above). Some high-end venues admit they need to replace a bulb in one of their projectors and so they have to cheat the image playback by cranking brightness or contrast! Yikes! Watch what happens to the 'cheated' image. The whites get blown out, the blues are off and the list goes on. Part of the problem is that many ceiling-mounted projectors need cherry pickers to access them - and not when there are people in the room. Ask how much you are paying for the rental!

How many lumens of brightness? It depends on the playback angles and room light ambience ( or 'ambiance', for slicker pronunciation):

- Lumens are not the only answer - contrast ratio is important, too (ratio of lightest to darkest in an image). But, the method of measurement is also considered ('full on/full off' VS 'ANSI' checkerboard - a google search will suffice for more info).

In the real world of presentation AV, I have found that a floor-level front-projected image for up to 200 people with a projector of 2000 lumens and CR of 2000:1 works very well - but not with every projector - that's why I always rely on the Canon LV series (no endorsement, just preference). They have a wide zoom as well.

For a ceiling-mounted front projected image, with a long throw, 3000 or more would be best. This can cover a few hundred people just fine. But, the added brightness only works when the lights cannot shine in people's eyeballs! So, 3000 or more lumens on the floor should be used with caution.

Rear-projection - you can use higher lumens, especially with a larger audience, BUT how far must you bring the screens out to get a big sized image? Also, there are 'hot-spots' on rear-projected images - a little distracting for viewers.

By the way, stated lumen count does not always mean actual lumen count. Some may be off by a couple of hundred or so lumens when tested by a third party.

This information is based on actual useage throughout many years of AV support for live events, not product literature sales information.

As always - Presentation-AV.com: "For when you can't rewind."

Buck Moore
Live Event AV Specialist