Some tips and techniques to achieve proper projection.

Image projection has been around since the late 19th century, and people have been working on ways to make projected images look better for a long time. In fact, there is no single way to summarize all of the different improvements that have been developed over the last half-century. But here are some tips and techniques that have been helpful in real-life projects.

The first step on the road to a well-projected image is to simply figure out if you even need to project. Flat-screen display costs continue to drop, but there is a sweet spot with regard to image size and cost. If you need an image that is 8 feet wide, it’s still cheaper to project. If you need an image that is only 4 feet wide, there are a number of economical and easily installed flat-screen display systems that probably make more sense. The rule of thumb that I typically use is to take the distance from the farthest viewer and divide that by four to come up with a recommended screen width (L/4=W). So you basically have to consider image size and cost first. Once you have determined that front projection is suitable, you can move on to the next step.

ASPECT RATIO
The second step is to determine what aspect ratio screen you will need to use. There are several out there to choose from these days. There is the venerable 4:3 ratio, the 16:9 ratio, and now there’s 16:10. I usually make this decision based on the projector that I’m eyeballing for the project. It’s best to match a screen with a projector and not try to scale your video after the fact.

The third step on this well-travelled path to projection is to locate your screen and make sure it works with the surrounding architecture. You can’t just slap any projection screen into a room without thinking about a few things. The first thing you will want to know is exactly what part of the room could be considered the “front.” It sounds simple, but oftentimes it’s a bigger issue than you think. A good rule of thumb is to make the “front” of your presentation space directly opposite the entry. Another thing to consider is lighting. Make sure that there are no pendant fixtures that could obstruct sightlines and that any lighting near your projection screen is circuited such that it can be turned off when there is an image being displayed.

SCREEN TYPE
Now that you have your screen sized and located, it’s time to actually pick out the type of screen and its features. There are several good projection screen manufacturers, and all of them offer a variety of options. To keep things simple, I’m going to discuss common options among the many manufacturers in this space. The first option I always consider is whether or not to use a tab-tensioned screen. This is when a manufacturer puts tabs with a weighted cable along the side of a projection screen. These tabs then stretch the screen surface, keeping it nice and flat. If the projection surface is not flat, parts of the image may not be in perfect focus.

The next option you will want to consider is the projection surface itself. Usually, I just use a matte white surface, but there are surfaces that can actually provide a brightness “gain.” If you have a limited budget and your projector is not that bright, you might want to consider using a beaded projection surface with some gain. A drawback to gain screens is that off-axis viewing suffers.

Another option to ponder is how your screen will be controlled. If you are using an electric screen and a control system, you will want to lower and raise your screen with a low-voltage control option. I also always recommend that you put a standard wall switch in as well, in the event of control system failure.

PROJECTOR
The screen is sized, located, and your options have been chosen; now all that’s left is pairing it up with a projector. It’s always a good idea to make sure that you have an area in your ceiling that is ready to receive your projector. I always tell architects that the projector will reside 1.5-2.2 image widths back from your projection screen. That is because most projectors have optics that let them operate in that distance range. You can buy short and long throw lenses, but the 1.5-2.2 range is usually the cheapest one to utilize.

These criteria are just some of the many different things that should be noted when selecting a projection screen. They are basic, and most often, the basics are enough to get by. So on your next project, keep the basics in mind and you should end up with a good looking image and happy users.

Joey D’Angelo is a principal consultant with Charles M. Salter Associates in San Francisco, CA, and specializes in AV/telecommunication systems. He can be reached at joseph.dangelo@ cmsalter.com.