Throw ratio is key to selecting the right location for a projector. In the projector manual, throw ratio might be expressed as a ratio or distance.

* throw ratio: 1.8:1 which means 1.8 ft of throw distance per foot of screen width.

* throw distance: 9 ft of throw distance to get a 60" wide image.

Armed with the data on your projector, here are a few simple ideas to help you find your location on the ceiling.

Photo Courtesy of Sanyo
Photo Courtesy of Sanyo
Projector Throw Distance

You will need to be aware of two things when trying to determine the distance your projector should be mounted from your screen. You will need to find out the width of the screen and the throw ratio of the lens on the projector. Then you need to plug in your screen width and throw ratio numbers into this simple formula (Screen width X Throw ratio = Throw distance).

Well there you have it folks. If you don't know the throw ratio, no need to worry. The manufactures provide that for you on the projector's specification data sheet. Typically it will show you a range 1.8 - 2.1 throw ratio. Plug both throw ratios into the formula and this will provide you with a throw distance range for the provided lens.

If the projector specification data sheet only provides you with a single digit number, this will indicate that the projector is equipped with a fixed lens with no zoom capability. This will make the install a little trickier because you will have to have exact placement of the projector in order to appropriately accommodate the screen.

Selecting a Projector Based on Throw Ratio

For those of you who are in the planning stage of your room or haven't figured out which projector you are going to purchase, there is a quick rule of thumb.

Plan on a throw ratio of 2.0. For example, if your screen is 5 ft. wide, then the projector needs to be 10 ft. away. This will give you a ball park figure of how far the projector will be away from the screen. All projectors have a set throw ratio, but typically your standard presentation projector will have a range of 1.8 to 2.1 throw ratio.

Expand Throw Distance Choices
Photo Courtesy of BenQ
Photo Courtesy of BenQ
Projector Lenses

Now what if you have done the calculations and the location to mount the projector is just not a doable situation? This is especially true for church situations or auditoriums where the projector has to be placed at the back of the hall.

For these applications you will need to buy a special lens for the projector. There is also short throw applications that will require a special lens. Rear projections almost always require either a mirror system or a short throw lens.

Sanyo, Christie, and Panasonic are all good projector brands to look at if you have an application that will require a long and short throw projection system. One thing to note is most of the manufactures will offer two versions of their install projectors. One with the standard lens and one version with no lens. You will see this version noted with an L on the end of the part number.

Purchasing the projector without the lens will typically save you about $300.00 off of the standard version. Long and short throw lenses, with and without zoom features, sell separately for $700 to $3,500. The price depends on the complexity of the projector lens equipment.
Throw Ratio Formulas Play Backwards - Like Beatles Albums

Now what if you are a contractor or an installer and you are looking to spec a job? All the customer has given you is the size of the screen and the location that they want to place the projector.

Well how do I use screen size and projector location to spec out a projector? There is a way. You can use the screen size and the distance between the screen and the projector to find out your throw ratio. Once you know your throw ratio you can then find a projector that accommodates your specified throw ratio.

Now, can I use the same projector throw distance formula to find out the throw ratio? Well yes but we need to change up the formula a tad. Here is the formula that we would use (Throw distance divided by the screen width = throw ratio).

Using this reverse engineering will help you find a projector with a lens that can accommodate your application.

Hopefully these ideas will help you in your planning and pre-planning stages of piecing together your presentation room.