Choosing a Projector

See if this scenario sounds familiar to you in any way: Mark needs a new projector for his facility but he’s not sure what to get. To avoid buying the wrong equipment, he talks to one of the people in charge of “tech” at his organization. The suggestion comes back that surely a 3500 lumen projector will be plenty of oomph (a good tech term) for the room. An order is placed and two weeks later, Mark has a new projector. Not only that, they also purchased a shiny new ceiling mount to hang their oomphy projector.

Mark and Mr. Tech get into the facility on a Saturday afternoon to install the projector. The first thing they do is try it on a cart to see where it should be installed. After turning it on and waiting for it to warm up, they begin to wonder how long it will take to get to full brightness. After a few moments, they realize it IS at full brightness, which will be somewhat dim for this room. Ok, they can deal with that. They roll the cart back to the spot where they would like to install the ceiling mount, only to find that they cannot zoom the projector to fill the screen completely (or it is too big and they can’t get it small enough). When they find the spot that actually works, they find they cannot install the ceiling mount because there’s a big (you fill in the bank… light, beam, etc) in the way. So… now what?

This scenario is, unfortunately, all too familiar in churches and businesses everywhere. How do you know what kind of projector to look for? Where do you start?

Considerations

There are many factors that come into play when choosing a projector. Let me address just a few that will get you pointed in the right direction. Here are a few questions you need to consider:

1. What is the intended use or application? Is this for a classroom or boardroom? Maybe it’s a portable church. Is this an established room that needs a permanent install? Each application calls for a different solution and it’s all too easy to grab the wrong projector, pay too much money for too much power, or undershoot your needs.

2. What is your screen size and ratio? Do you need 4:3 (standard) or 16:9 (widescreen)? While most projectors will adapt to what signal your sending, it’s always best to have a projector that’s native to your ratio. Otherwise you’ll end up with wasted screen space in the form of letter boxing or columns. You’ll also need your actual screen size for calculation as we’ll discuss in a moment.

3. What is your distance available for projection? This will be a major determination for your projector concerning brightness and throw ratio.

4. How much ambient light is present in your room? Do you have a large number of windows? What about projected light? Are your lights suspended from a low ceiling, forcing your lights to be lower than a 45 degree angle and possibly throwing light on your screen?

5. Are you planning front projection or rear projection?

Terms of Endearment

As you research projectors, you’ll see many different terms being thrown about. Without a little background, it can get confusing quickly. I will cover a couple of these here and use laymen terms, since that’s what I am for the most part.

The most common term you will hear is “lumen.” A lumen, a defined by the International System of Units, is a derived unit of luminous flux. This is a measure of the total amount of visible light emitted by a source. Radiant flux measurements indicate the total power of all light emitted, independent of the eye’s ability to perceive it. I doubt you’ll see any documentation referring to radiant flux. You should pay attention to the luminous flux, or ANSI Lumens.

ANSI? American National Standards Institute. If you see one projector’s documentation refer to lumens and another to ANSI Lumens, have no fear. It’s the same thing.

One less common term, but very important for our purposes, is “foot-lambert.” The foot-lambert is used in the motion picture industry for measuring the luminance of images on a projection screen. A foot-lambert is roughly equivalent to lumens per square foot.

The Society of Motion Picture Engineers (SMPTE) recommends a screen luminance of 16?foot-lamberts for commercial movie theaters. Keep in mind that a theater is a completely controlled space with virtually no other light present. I know that our local mega-movie complex actually runs their digital screen projection as low as 8 foot-lamberts, which seems ridiculously dim. It apparently works.

It will never be as dark in your facility as it is in a movie theater. It’s been our experience at Moyers Group that 35 to 40 foot-lamberts is sufficient for controlled lighting. 45 to 50 lumens per square foot is good target for a room with average ambient lighting.

Beyond that, it gets harder to figure. For instance, if you have low hanging lights that illuminate your stage at a low angle, it may throw unwanted light on your screen. A front-projection screen is designed to reflect light. If your screen is receiving light from your projector as well as light from your stage set, one or the other will win. Usually stage lighting is much stronger.

Regarding ambient light, “average” ambient light is also hard to measure. I recently worked with a church that had a large number of very large windows. They bought a projector that gave them a whopping 95 foot-lamberts. As it turned out, even that left them too dim for the back half of the room.

Figuring lumen strength: Not guess work

So how do you figure out what size projector you need to get the foot-lamberts you think you require? This is where screen size comes in. Simply figure your screen’s square footage and multiply by the desired foot-lambert level. This will give you the amount of lumens you need in a projector.

(screen width X screen height) X foot-lamberts = required lumens

For instance, if your screen is 14′ x 10′, that gives you 140 square feet of screen. If your target is 50 foot-lamberts, multiply 140 x 50 and you find that you’ll need 7000 lumens to achieve your goal.

If you already have a projector and are wondering why you can’t see anything, reverse the formula. Let’s say you currently have a 4000 lumen projector on that same 140 sq.ft. screen. Divide 4000 by 140 and you see you’re projecting less than 30 foot-lamberts.

Throw Ratio: How much room do you have to project?

Now that you know what lumen size to look for, the next major concern is your throw ratio. Every projector has that “sweet spot” that allows you to zoom in or out and fill the screen perfectly. This is also easy to figure if you have access to the technical specs of your projector.

The projector throw ratio for any given screen size is distance/width. For instance, let’s say you know you need to mount your projector 15 ft. out from the screen, and the projected width of your screen is 12 ft. Distance divided by width is 15 / 12. Your throw ratio is 1.25. Now you know that you need to look for a projector that has a range of throw ratios that includes 1.25. Nearly every projector has the ability to zoom in or out, and so the throw ratio of any given projector varies by several points. The greater the zoom, the greater the range of ratios. If the projector you are considering has a throw ratio of .8 to 1.5, you are good to go. If it is 1.2 to 1.6, you are on the outside edge, but still likely okay. If you have .6 to 1.0, you have a short throw projector and it will not work for this setting.

Conversely, if you know your screen size and the ratio of a projector and need to know how far out to place your projector, simply figure width X ratio. Your 12 ft. screen x 1.25 throw ratio tells you to place the projector at 15 ft. for best results.

DLP vs LCD

Another area of misunderstanding comes in the difference between DLP and LCD projectors. Which one is better and what do you need? Allow me to quote big words from Wikipedia:

“DLP (Digital Light Processing) is a trademark developed and owned by Texas Instruments. In DLP projectors, the image is created by microscopically small mirrors laid out in a matrix on a semiconductor chip, known as a Digital Micromirror Device (DMD). Each mirror represents one or more pixels in the projected image. The number of mirrors corresponds to the resolution of the projected image.”

In other words, it’s all about the reflection of the incredibly small and numerous mirrors.

“LCD (Liquid Crystal Display) is a transmissive technology. Projectors typically send light from a lamp through a prism or series of dichroic filters that separates light to three poly silicon panels ? one each for the red, green, and blue components of the video signal. As polarized light passes through the panels, individual pixels can be opened to allow light to pass or closed to block the light. The combination of open and closed pixels can produce a wide range of colors and shades in the projected image.”

Just think of it as a massive array of lights with gels that have been microscopically shrunk by the guy on “Honey I Shrunk the Kids.”

Which one is better? It depends…

Both technologies are good, but each one has different strengths. Think about your application and consider this. A DLP projector excels at motion. Movies and football games are great on DLP. They also have sealed optics, which keeps it nearly maintenance-free. The downside? They are generally more expensive and not quite as vibrant in color (unless you have a 3-chip DLP).

LCD projectors have richer, truer colors, which make them well suited for computer graphics and still images. They can certainly handle motion, but you might see a bit of ghosting. Positive? They tend to be a bit easier on the budget.

If you’d like the best of both worlds and are willing to lay out the cash, a 3-chip DLP gives you true color and great motion. You get what you pay for.

Conclusion

This is a lot to swallow in one sitting, but I believe it’s a good overview of the essentials. If you have a good idea of your needs, know your target foot-lambert level, know your desired throw ratio and have an idea of your preference of projection technology, you are way ahead of the game. You’ll also be able to talk intelligently with your preferred sales-tech.