What Is a Throw Ratio?

by Kyla Chele Cambrooke
A projector displays images on a wall.

A projector displays images on a wall.

When you want to project an image, slide show or video on a screen or a flat surface, you may opt for a projector. Sometimes people refer to a projector to a digital projector, video projector or LCD projector. It is usually a portable device you can set-up in various locations. Whether you are preparing to set-up a projector in a classroom, media room or conference room, knowing the throw ratio helps you place the projector in the right location.

Throw Ratio Formula

The throw distance is the distance between the edge of the projector's lens to the wall, flat surface or screen you show your images. This helps you determine the location of the projector in the room. The image's width (w) in relation to the throw distance (d) is the throw ratio (d/w).

Ratio Example

There are several ways to calculate the throw ratio with the d/w = throw ratio formula. You can simply insert the numbers in the formula to determine the throw ratio. For example; if the screen width is 10 feet and the throw ratio for the project is 1.5 to 1.8, you can sit the projector 15 to 18 feet from the display screen.

Using the Zoom Lens

A zoom lens can affect the throw distance. Zoom lens give you the ability to increase or decrease the size of an image without changing the projector's location. This feature on a projector helps you prepare a room when you cannot change the size of the screen or the location of the projector. Additionally, if you opt for a different screen size in a fixed location, it is easier to change the screen size without moving the projector by using the zoom lens.

Zoom Ratio

Projector zoom ratios usually range from 0.4 to 2.1. However, you can purchase special optional lens to give you lower or higher zoom ratios outside the original projector's lens capability. The image size can change by adjusting the zoom lens. Video projectors equipped with short throw lens can display bigger objects or images at a lower throw distance. Non-mounted projectors with short throw lens allow you to place the projector in several locations.

Photo Credits

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