Projector Brightness Advice
When selecting from the huge range of projectors available, you might be wondering if brighter is better. You usually end up paying more for higher brightness, so it's worth checking out if you really need it.
Home cinema users - you can skip this whole article, as all you need to know is that brightness isn't really important for home cinema, which is why there are very few quality home cinema projectors over 2200 lumens. Your time and money is better directed towards preventing as much ambient light as possible from hitting the screen surface, and get a specialist home cinema projector with high contrast and a good video processing chip.
Everyone else - for uses other than home cinema, the formula to finding the right brightness level for you is a little more complex and is explained below. But first...
Some brightness basics
Brightness is measured in ANSI lumens.
Trivial fact #1: ANSI is the American National Standards Institute, who came up with a way of measuring projected brightness. Unfortunately, though, the nice people at ANSI left a little room for 'scientific interpretation' when this standard was launched. Hence a 1000 lumen projector from one manufacturer isn't always as bright as a 1000 lumen projector from another, so don't take these measurements too literally.
The other basic but important point to note is that a projector cannot make the surface it projects on to any darker. Consequently, the brightness (or lack of) that you see on the screen with nothing projected on it is the darkest black you could possibly get from a projector.
Chances are that unless you've blacked out the room, the surface of the screen won't look black - it will look some shade of grey depending on how much natural or artificial light is in the room. What really bright projectors do is they flood the image with so much ultra bright white light that the grey you see with the projector 'feels like' black, because it's so far removed from the white light. This effect works pretty well when you've got a lot of bright colour in the image you're projecting, but not so well if you're projecting something dark, like a Star Wars film or that old x-ray of your granny after her hip operation.
Trivial fact #2: This is one reason why in the early days of Powerpoint presentations so many people used yellow text on a blue background. Projectors weren't too bright, so it made sense to use two bright colours with good contrast against each other.
The bottom line is that you can achieve better results by cutting out ambient light on the screen than by just paying for a brighter projector. You may, however, want to keep a certain degree of ambient light if you're a presenter and you want eye contact with your audience.
How to choose the brightness that's right for you
Now we've done the basics, here's how to apply them to choosing the right amount of lumens for you. There are three factors you need to consider:
Ambient light - is the greatest consideration. If you're on the move and don't know what level of ambient light you're likely to encounter when you set up your projector, opt for a high brightness projector (3500 ANSI lumens or higher).
Screen size - The bigger the image you're projecting, the less concentrated your projector's brightness is going to be on each square inch of the screen. An average screen size is about 200cm wide. If you start going bigger than that, consider upping your brightness accordingly.
Subject matter - If you're projecting detailed, intricate work then it's important that everyone can see the details, so buying a high brightness projector helps there. However, if you're just projecting large, bold words then it shouldn't be as much of a priority.
Footnote: Some pundits would say that audience size is a factor to consider. We've left it out, partly to upset the pundits but also because we assume you'll use a screen that's big enough for the guys at the back to see your content.