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WHAT IS PROJECTOR THROW DISTANCE AND PROJECTOR RATIO?

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There are several important projector specifications which you will need to take into account when comparing projectors.  Understanding product technical specifications and how they differ will affect determine how well suited a projector is to your presentation environment.  One major technical specification that relates to the projector''s lens, which it is very useful to understand, is the projector''s throw distance.

ProjectorSourceCanada.ca will help explain what throw distance is, how it is calculated, and how it will affect how you use the projector.  Understanding throw distance, including short throw distance lenses, long throw distance lenses and applications where shorter and longer throw distances may be required are of utmost importance when selecting a projector.

Calculating throw distance


Throw distance is measured and calculated by distance between the projector''s lens to the projection screen that the image is being cast onto (i.e., the distance that the image is "thrown").
 
Throw distance is the basis for determining the projection screen size possible for use - a common standard for projector throw distances is one foot (30.5 cm) of projection screen width to every two feet (61 cm) between the projector''s lens and the screen.

A smaller throw distance as opposed to a larger throw distance means a smaller possible distance between the projection screen and projector, if the size of the projected image is kept constant.

What is a projector throw ratio?


The throw ratio of a projector is the result of dividing the distance between the projection screen and the projector''s lens by the width of the image being projected, or more simply:

Screen width x Throw ratio = Throw distance


When deciding what projector to purchase, where to place your projector or projection screen the throw ratio figure is all you need to know. If you know you want to use a projection screen that is ten feet wide and you know that your projector''s throw ratio is 1.8:1 (which means 1.8 ft of throw distance per foot of screen width) then you should place your projector 18 feet away from the projection screen since 10 multiplied by 1.8 equals 18.

Why are throw ratio and throw distance important?


A projector''s throw distance is vital when determining how far to place the projector and the size of projection screen required.  By measuring the throw distance, you can decide the positional adjustments needed to accommodate a predetermined projection screen size or projector placement.

If these alterations aren''t possible (for example, if the projector is being installed in an auditorium and needs to be at the back of the hall) then you may need an extra or different lens to increase or decrease the projector''s throw distance. If the projector is too close to the screen then a short throw lens may be required, otherwise the image may appear pixelated. This can be an issue with interactive whiteboards where the projector is often placed close to the board. On the other hand, if a projector is placed too far from the screen then the projected image may appear unclear if a long throw lens is not installed. Some projectors are specifically designed to have either long or short throws distances, and thus ship pre-installed with specific these specific lenses. However, the majority of projectors will need an external lens to be installed to accommodate projector placements at extreme distances close to the projection screen or very far away from it.

The advantages of short throw distance lenses


A shorter throw distance will result in a bigger picture being projected, if the distance between the projector and the projection screen is kept constant. For further effect a short throw lens can be used to project an even larger image. Some projectors, such as the Hitachi X275, come pre-installed with a short throw lens and can thus project a 48-inch diagonally wide image from only 4 feet way. Projectors with short throw distances are suited to those people that require portability, such as road warriors, or for those people that need to use their projector and screen in smaller environments such as modest home theatre rooms, hotel rooms or small meeting rooms.

The advantages of long throw distance lenses


A longer throw distance allows for smaller, sharper images to be projected from further distances away. A longer throw lens is preferable if you intend to use your projector in large, expansive surroundings such as in large conference rooms or houses of worship where the projector is required to be hidden at the back of the building. In these situations a long throw lens will most likely be required to make sure that the quality of the projected image is maintained while moving the projector further away from the screen.

We hope you enjoyed this article by Projector Source Canada.  For more information or to purchase a display and projector for your business or home, visit us online at http://www.projectorsourcecanada.ca.

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