When buying a new projector, there are a whole bunch of specifications you need to consider in order to make sure that the device you get is suitable for your particular needs. These specs play a great role in determining how the projector performs in different environments. One such important measurement is throw ratio.
When it comes to projectors, throw is the distance between the lens of the device and the screen on which the output is displayed. Throw ratio is relation between the throw distance and the width of the projected image (often represented in feet).
Why is throw ratio important?
The throw ratio value tells you how far you have to place the projector from a screen that is 1 foot wide to get a full-sized image, which can be extrapolated to get other values. For example, if you have a screen that is 10 feet wide and a projector has a throw ratio of 2.4:1, you need to place the device 24 feet away to fit the entire width (since 2.4×10 is 24). Most projectors have a throw ratio range with 1.8 – 2.2:1 being very common.
How can I use throw ratio to decide where to place the projector, if I know the width of the projection screen?
Using the throw ratio value, you will be able to quickly calculate throw distance for a specific screen width since: Throw distance = throw ratio x width of the screen
This will also help determine if the projector is suitable for the application you have in mind. For example, if you want to project onto a screen that is 20 feet across using a device with a throw ratio of 1.8:1, you will need to place the projector 36 feet away (1.8×20 = 36). But, if the room you are planning on using it is smaller, this device may not be useful for you.
What if I have already decided where the projector will be?
If you already know where you are going to place the projector, you can use throw ratio to determine an optimum screen size.
Width = throw distance / throw ratio
Let’s assume that the projector is going to be placed 20 feet away and has a throw ratio of 1.8:1. Using the above formula, we can figure out that the width should be 11.11 feet (= 20/1.8). Your projector screen has to be of this width (and appropriate length which can be determined from the aspect ratio) for the output image to fit it fully.
Can the throw ratio only be used to measure distances in feet?
No. Since it is a ratio, it can be used to calculate different distances even if they are in meters or yards or any other unit. But do keep in mind that since all projectors have fixed resolutions, sitting too close to the screen will result in pixilation. Use the throw ratio in conjunction with the resolution of the projector to determine its location and screen size.