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Category Archives: Optoma

Active and Passive 3-D Projectors: What’s the Difference?

In the last decade, technological advances have greatly improved 3-D projection. Now, 3-D viewing is possible anywhere and anyone can set up a 3-D projector at home for a few hundred dollars.

But there are many different types of 3-D projectors. How can you determine which one is right for you?

First, you should know there are two main types of 3-D projectors: Active 3-D or Passive 3-D projectors. Both work in a similar way. They create the 3-D image by showing each eye a slightly different picture. By displaying these slightly different images – either via the projector or with special shuttering glasses – depth is created and the picture jumps off the screen.

3D Projectors
3D Movies of the 1950’s

Here are a few things you should know about passive and active 3-D projectors:

Active 3-D Projectors

Active 3-D, also known as powered 3-D, is most commonly used for home theater or gaming set-ups. The reason: It’s more affordable and it can be easier to set up. Plus, almost all of today’s active projectors have 2-D and 3-D capabilities, like the BenQ W1070, which make them great for home theaters.

Active 3-D projection relies on special glasses. The lenses of these glasses are designed to quickly alternate between opened and closed, so that each eye sees a slightly different picture. A high-speed projector capable of showing 60 or more frames per second is required in active 3-D projection. If not, the image begins to flicker.
There are several advantages to active 3-D projection. First, each eye sees a full HD image, which as I’ll explain later, isn’t possible with passive 3-D. Plus, any screen works, i.e. a wall or a bed sheet. Passive 3-D, on the other hand, requires a special screen.

The disadvantages? First, the glasses are more expensive. They also must be charged and they can fail. Although prices have come down, a pair of premium glasses can cost $100 or more. The lenses also are darker, and thus, the image can be darker.

Passive 3-D Projectors

If you’ve ever seen a 3-D movie at the theater, you’re familiar with passive 3-D projection. With this set-up, the projector creates two simultaneous images – either with light polarization or spectral decomposition – and the viewer’s glasses make these different images visible to each eye.

To create these two images, some set-ups include two different projectors to display the different images. But today’s movie theaters use a single projector that uses circular polarization to achieve the two images. That’s a main reason these set-ups are more expensive; they require advanced projectors to achieve the image.

Passive 3-D is also more expensive because it requires a specialized silver screen, although the most advanced projection systems don’t require the screen. Although the silver screen reflects more of image, in turn creating a brighter picture, it can add to start-up costs.
The main advantage is the cheaper glasses; they cost just a few dollars per pair or less. That’s one reason theaters opt for passive projectors. Plus, prices are coming down, which is making these more economical for home use. For instance, the Epson PowerLite W16SK 3D 3LCD costs just under $2,000, and while costly, it makes the set-up possible for home theaters.

Which 3-D Projector Is Best for Home Theaters?

High-speed active 3-D set-up makes the most sense for home theaters and gaming rooms. Why? First, the majority of today’s projectors are 3-D ready and they’re affordable: i.e. the 3-D ready Optoma HD131X costs about $600. Plus, active 3-D glasses don’t cost as much as they used to; there are budget, third-party glasses available in the $15 to $35 range.

That’s why active 3D projectors are ideal for home theaters: budget set-ups won’t break the bank, and technology has improved the image quality greatly. Today, you can truly achieve an immersive 3-D experience in your living room.

How to Mount Your Projector for the Perfect View

Where’s the best spot to mount your home theater projector? Well, it depends on several factors and the type of projector you’ll be using. For instance, short throw projectors must be closer to the screen, while long throw projectors are better positioned further away.

Projector: short and long throw
Long Throw vs. Short Throw

You can calculate the best position for your projector easily. First, you’ll need to know screen width, throw distance — or the distance between the projector’s lens and the screen — and “throw ratio.” Throw ratio is very important for home theater configuration, and it can be found by dividing the throw distance and screen width. For projectors with zoom capabilities, throw ratio is a range; for instance the 3M X50 has a throw ratio between 1.51 and 1.82.

Using the throw ratio, you can determine the screen size and throw distance. For example, a projector with a throw ratio of 2.0:1 placed 15 feet from the screen would project an image that is 7.5 feet wide. Here’s the equation: Throw Distance (D) / Throw Ratio (R) = Screen Width (W). Conversely, with screen width, you can determine throw distance: W R = D. So for a 7.5-foot-wide screen, your projector would need to be 15 feet away: 7.52= 15 feet.

projector throw

Mounting Short Throw Projectors

Short throw projectors are perfect for home theaters, because they can be much closer to the screen and achieve great image results. These projectors have smaller throw ratios that are usually below 1:1. For example, a short throw projector with a 0.6:1 ratio could achieve a 7-foot-wide screen from just 4.2 feet away. Because of this, short throw projectors can achieve great image results even when mounted near the floor.

Mounting Long Throw Projectors

The throw ratio for long throw projectors is larger, and they must be further from the screen. That’s why long throw projectors are often used in conference halls and college classrooms. Here’s an example: If you wanted an 8-foot-wide screen at a 2.5:1 throw ratio, the projector would need to be 20 feet from the screen. Because of this larger distance, ceiling or tabletop mounts are often the best option to avoid casting shadows.

Aligning Projector Lens and the Screen

Depending on the type of projector you own, you can determine where to position the center of your projector lens. For instance, some projectors have an “vertical offset,” which means the center of the lens needs to be slightly above or below the screen. For instance, the Optoma H180X has an 112% offset. This means that for a 100-inch-tall screen, the center of the H181X lens would need to be 12 inches above or below the screen.

projector lens offset

Conversely, some projectors have no offset. When there’s no offset, the center of the lens should be at the top or bottom of the screen. And finally, some projector lens must align horizontally with the center of the screen. Fortunately, many home theater projectors have horizontal or vertical shift capabilities. This means the picture can be adjusted to fit the screen. You could just look at the owner’s manual if you are doubtful or cautious.