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## Relationship Between Screen Size and Projection Distance

It is commonly believed that having at least a 100-inch screen can really immerse into an ideal home cinema experience. Though a large space is needed in order to project onto large screens, today’s short throw and ultra-short throw projectors, or throw ratio around 1.13:1,  make it easy to enjoy 100”+ screen sizes in rooms of any size simply, especially in small apartments.

Take throw ratio 1.13:1 as an example, the relationship between projection distance and screen size is defined as

Throw Ratio = Throw Distance / Image Width,

which can calculate a distance as 8.2ft from the wall for projection of a 100-inch image with a 16:9 aspect ratio (image width is approximately 7.2ft). Look for information about screen size and distance, typically expressed as "screen size @ distance" from the screen. In this example, the specification "100"@ 8.2ft " means that the minimum distance you will need is 8.2ft from the projector to the wall to get a 100-inch screen size, which is an ideal projector set up in a space of about 21 sq. ft to 32 sq. ft, such as a small apartment when it is needed to project a 100-inch picture.

## Where to Place Projector Decides Projection Distance

Therefore, the projection distance starts from your room size and where the projector will be placed also its distance to the screen or which wall to project the image. To select the ideal projector for your home, you will need to measure the length and width of the room and use the maximum distance the projector can be placed from the screen to filter for the specific projector model that will meet your ideal screen size from that distance. If the space has an irregular shape, such as an L shape or a polygon, first confirm furniture placement, then measure the distance between the two walls as the reference for purchasing a projector. Keep in mind the best setup position is where two walls are furthest apart in the space.

There are many choices in terms of machine size and projector lens design. Among all existing projectors, a throw ratio around 1.13:1 is the most common design that has the lens in the front of the projector. These designs can require distances as short as 8.2ft to project a 100-inch screen, which is the most common throw distance setup in limited space or small apartments.

Besides, some projectors with the short-throw lens can save more space from the projector to the wall, offering a shorter projection distance for the same 100-inches screen (100"@6.6ft). There are also models with the lens placed inside the projector body to project images upward onto a screen above and behind the projector body, and these ultra-short throw models only require a distance of less than 3.3ft to project a 100-inch screen. So it’s easy to enjoy large screens even if the room is smaller than 6.5ft2.

For spaces where the projectors cannot be aligned to the center of the screen, simply select a model equipped with vertical/horizontal keystone correction or lens shift to experience the immersive thrill of a huge screen that’s only available at theatres.

## Off-centered Projection Can be Corrected

If the projector can be mounted on the ceiling or placed on a table aligned to the center of the screen, only the "screen size @ distance" information is needed when selecting a projector. But if the projector cannot be aligned to the center of the screen leading to screen distortion, the projector must be equipped with keystone correction or lens shift design. Some projectors offer vertical keystone correction, while others include both vertical and horizontal keystone correction. If the projector can be aligned to the center of the screen but must be tilted at an angle to fill the screen, then only vertical keystone correction is needed to project images fully and accurately. But if the projector cannot be aligned to the center of the screen due to room décor and must be placed by a wall or a corner, a model with both vertical and horizontal keystone correction is needed.

The difference between lens shift and keystone correction is that lens shift is a physical mechanism and keystone is based on digital correction. Lens shift allows the lens to move up, down, left and right within a certain range, so the projected picture can be moved vertically or horizontally without causing keystoning (trapezoidal distortion). So regardless of where the projector will be placed, simply select a model equipped with lens shift or keystone correction to enjoy 100”+ cinematic experiences right in your home theater.

Keystone Correction

Lens shift

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