Choosing A Projector For 3D House Mapping

Figuring out what kind of projector to get for this kind of project can be a little intimidating. In this article, we try to break it down to it’s simplest form so that you know what to look for. You need to pay attention to 3 main things: throw ratio, resolution, and brightness.

Throw Ratio: Go For Short Throw

Throw ratio is simply how big the projected image will be based on how far away your projector is from your house. Most projectors have about a 1.5:1 throw ratio which means for every 1.5 feet of distance the image will be about 1 foot wide.

Let’s say you plan on putting your projector on the sidewalk in front of your house and your sidewalk is 30 feet away. At that distance, a standard throw projector will produce an image about 20 feet wide. Unless you have a very small house, that is probably not big enough. You will need a lot more distance to get an image large enough to cover your whole house. If you have a large property or your neighbors across the street don’t mind you projecting from there, it is possible that you could get enough distance to make it work.

However, most people will want to use a short throw projector instead. A typical short throw projector has a throw ratio of about .5:1. That means for every half foot of distance the image will be about 1 foot wide. 30 feet of distance with a short throw projector will get you an image about 60 feet wide! That will definitely work for the majority of houses.

Short throw projectors tend to be more expensive because it costs more to make the lenses. As you might expect, they are also a bit harder to find. Unfortunately, the exact throw ratio is often left out of the projector specifications which can be confusing. However, the term “short throw” is an important feature, so it will definitely be mentioned if the projector has it. On the other hand, if the description of the projector does not mention “short throw”, then it almost certainly is standard throw because that is most common.

You may also see ultra short throw projectors. They will produce an even larger image with less distance, but for most situations that is probably overkill.

Resolution: Higher Is Better

The resolution of the projector determines how sharp the projected image will be. Since we are blowing up the image big enough to cover a house, it makes quite a bit of difference in the final look. A projected image is made up of thousands of tiny little squares or pixels. The more squares there are, the sharper the image. Naturally, you will want the most pixels you can possibly get, but the more squares, the greater the expense.

It isn’t always easy to tell exactly what the resolution of a projector is. Some manufacturers will call their product an HD projector, but they are referring to the resolution of the video input rather than the output. That is misleading because almost any projector can accept HD video input, but it has nothing to do with the quality of the image the projector produces.

When checking the resolution of a projector, the term you want to look for is “native resolution”. Native resolution is the highest resolution the projector can produce. The industry has established acronyms for certain projector native resolutions and you will often see these when projector shopping. Below are the most common:

SVGA = 800 x 600 (800 squares across and 600 squares down)
XGA = 1024 x 768
WXGA = 1280 x 800
WUXGA = 1920 x 1080

There are also two types of HDTV resolutions you will see:

720p = 1280 x 720
1080p = 1920 x 1080

Any of these resolutions mentioned above will work for this type of project, but the larger the numbers, the sharper the image will be. We don’t recommend that you use anything less than 800 x 600 resolution for this type of project and then only on smaller houses. 1024 x 768 seems to be the sweet spot in terms of quality for the price. 1920 x 1080 is the best and that is the same resolution at which we provide the videos. Anything higher than that is overkill.

Brightness: Brighter Is Always Better!

A bright projector will make the difference between a murky, dark image, and a crisp clear one. If your home has a lot of ambient light from street lamps or other lights, then you will definitely need a bright projector to overcome that.

Brightness is measured in “lumens”. One lumen is approximately equal to the amount of light a lit candle will produce. A standardized procedure for testing projectors for brightness has been established by the American National Standards Institute (ANSI). The best measurement of brightness for a projector will always be ANSI lumens, so that is something to look for. Some projectors claim to be brighter than they really are because they are using a different method for measuring brightness.

We recommend that your projector produces about 2,500 ANSI lumens or even better, if possible. You could probably get by on 1,500 lumens if the area around your house is very dark, but we wouldn’t recommend going any lower than that.

Beware Of LED Projectors!

LED or Light-Emitting Diode technology is all the rage right now. It is a new, more energy efficient way of producing light than traditional light bulbs. Cheap LED projectors have flooded the market in recent years.

We highly recommend that you go with a projector that has a traditional Halogen bulb rather than LED. Projectors need to produce a lot of light and Halogen is just much brighter for the money. LED technology is rapidly improving, but it will be a long time before LED projectors with enough ANSI lumens to match Halogen will be available for a reasonable price.

Many people say that LED projectors have the “appearance” of being three times brighter when compared to a Halogen projector because they have a more bluish light. In fact, a new measurement called “LED lumens” has been established in an attempt to account for this apparent difference. In my opinion, it is hogwash. A lumen is a lumen no matter what source the light comes from. “LED lumens” are just a marketing ploy to confuse consumers and convince them that LED projectors are brighter than they really are.

The bottom line is that, if you see an LED projector, take the advertised lumens number, divide by 3 and that will give you the actual ANSI lumens. For example: an LED projector advertised at 3000 lumens is probably only 1000 ANSI lumens.

Not Much Difference Between LCD Versus DLP

There are 2 types of prevailing digital projection technologies: LCD (Liquid Crystal Display) and DLP (Digital Light Processing). DLP uses thousands of tiny mirrors to form the image while LCD is similar to the technology used in flat screen TVs. Both technologies work very well and neither seems to have a significant advantage over the other. I have heard from a reliable source that LCD projectors are slightly brighter by virtue of the way the technology works. I haven’t tested that theory and I actually use a DLP projector on my own house, but I thought I would share it anyway.

By the way, don’t confuse LED (Light-Emitting Diode) with LCD (Liquid Crystal Display). LED is a type of lamp producing the light. LCD is a technology used to form the image with the light.

Lasers Are The Future

Projectors that use lasers as the light source are hitting the high end market, but prices are falling and in coming years affordable laser projectors may be available to home users. Laser projectors can produce much, much brighter images than projectors with a traditional lamp. Lasers don’t produce any more light than traditional lamps, but they are just much more efficient in how they deliver that light to the screen. Here is a simplified explanation: A standard projector lamp produces white light. In order to show something blue on the screen the projector has to filter out all the light except the blue light. In that way, much of the light produced by the projector bulb is filtered away and wasted. By comparison, lasers only produce light in certain colors. So to show a blue object on the screen, the projector just uses a blue laser and all of the energy is used to project that blue object with very little wasted light.

Since brightness is so important for this kind of a project, this technology breakthrough could really help all of our displays! Currently, the least expensive laser projectors are around $10,000 but hopefully that price will come down in the next 5 years or so. We shall see!