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What Are the Vertical and Horizontal Keystones?

What Are the Vertical and Horizontal Keystones?

As a new or occasional projector user, you may not be very confident about diagnosing and troubleshooting problems you encounter while using the device.

And one of the most common problems is the keystone effect: vertical and horizontal keystones.

Join in as we discuss: What is horizontal and vertical keystone? And how does it happen?

We’ll also show you how to prevent it and rectify it when it occurs.

What Are Vertical and Horizontal Keystones?

Keystone correction on a projector

Horizontal keystone is the distortion that affects the left or right side of the image, more commonly known as horizontal keystone effect. It causes the image to lean toward the left or the right.

Usually, when the horizontal keystone effect strikes, the image will look like a trapezoid instead of a standard square or rectangular-shaped display image. And in this case, either the left or right side of the image will be elongated.

What would this look like on your screen?

In a frame that fits the screen, the image may fill the top and bottom parts of the screen. But the non-parallel sides of the image where the distortion has occurred will leave blank spaces on the screen.

These black spots will mark the parts where the image leans inward on one end and outward on the opposite end.

Vertical keystone is the distortion that occurs at the top or bottom of the image. It’s usually referred to as vertical keystone effect.

Images affected by the vertical keystone may have a top or bottom that extends outwards. But in some cases, both the top and bottom of the image extend outwards.

On your screen, this could look like:

  • a person with an abnormally long head or wide feet
  • buildings that are wider at the base but become narrow as you move toward the roof
  • objects with a distorted shape, for example, an uneven ball
  • skewed text
  • an image that is narrow at the bottom and wider at the top or vice versa

What Causes the Keystone Effect?

a teacher using projector to show the image for her class on the wall

The keystone effect, whether vertical or horizontal, occurs when the projector casts images at an angle.

This happens when the projector lens does not align with the center of the screen. And so, when you project a picture, the image does not hit the center of the screen.

The image is cast depending on where the lens is focused. If the projector lens is to the side of the screen, the image is cast either to the left or right of the screen.

This results in horizontal keystone distortion.

When the projector lens is above or below the center of the screen, the image projected is cast higher or lower on the screen.

This results in vertical keystone distortion.

Can You Prevent Vertical and Horizontal Keystones?

Fortunately, it is possible to prevent keystones.

And it’s all in how you set up the projector—a seemingly easy task but one that can take quite a bit of effort to get right.

How do you do this?

When mounting the projector, ensure that the lens faces the center of the screen. In other words, ensure that the projector and the screen align properly.

keep the projector square with the screen

Unfortunately, this may not always be possible.

Depending on the room design or what else is going on in the room, you may need to:

  • position the projector at the back of the room
  • place it on a particular side of the room

All these will affect the position of the lens with respect to the screen. As a result, you may find yourself dealing with keystone distortion.

You may get some reprieve if:

  • you’ve mounted the projector and
  • adjusted the throw distance and vertical angle

Doing this keeps the projector aligned with the screen. And because the two are in a fixed position in such a setup, you may not have trouble with keystone distortion.

But if your projector is not mounted, and you only bring it out whenever you wish to use it, or you’re working with a portable projector, you’ll probably deal with a fair share of the keystone effect.

How to Correct Vertical and Horizontal Keystones

Unless you take measures to correct them, vertical and horizontal keystones will not magically disappear.

Luckily, you can correct them. And you do that with keystone correction.

Keystone correction is available in one of two ways: digital and manual.

press screen fit button on projector for automatic keystone correction

Manual versus Digital Keystone Correction

Manual keystone correction is an old-school way of rectifying keystone distortion. It calls for you to adjust the projector manually to correct the image.

1. This could mean changing how you position the projector

Make sure the projector is on the same level as the screen and the lens points to the middle of the screen.

You may also need to change the placement of the screen even as you reposition the projector.

2. It could also mean physically adjusting the projector’s keystone button

Projectors with manual keystone correction have a button that you turn to adjust the picture. This button is located on the projector, on the control panel.

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So you move the button while observing the behavior of the image on the screen. Typically, you’ll rotate it clockwise or anticlockwise. On other projectors, move it left and right, depending on how it’s designed.

Keep turning the button until the shape of the image is fully restored.

Digital keystone correction is a built-in feature available in most modern projectors.

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The projector detects when keystone distortion has occurred and automatically corrects the error.

Not sure whether your projector has a digital or manual keystone feature?

Check under the projector settings.

Is there an Auto option under Keystone Correction? If there is, the digital keystone correction feature is automatically applied upon turning on your machine…

More often than not, brands use the term “keystone,” so the setting is easy to find. But there are exceptions. For example, Epson also uses Geometric Correction instead of keystone correction.

If you can’t see the name “keystone” and are unsure what menu item to check, look for the symbol H/V. That should be it.

In any case, consult the manual and you’ll know where to look. But just in case you can’t find your manual, the above should help.

Set the Auto option, and the device will automatically correct the distortion whenever there’s a keystone effect.

If you don’t see Auto in the keystone correction options, go back to Keystone settings.

Depending on the brand and model of your projector, you may need to select Enter to bring up the horizontal and vertical keystone menus. (Follow the prompts on the screen and you should find your way to the menus.)

The horizontal/vertical keystone adjustment screen that pops up may have +/- or </> buttons. Select the buttons to adjust the shape of the image as needed.

Keystone Correction Explained! | Projector 2 Min Tips

Conclusion

Vertical and horizontal keystones are image distortion effects.

They occur when the projector is not perpendicular to the screen.

So when the device casts an image, it sits high or low on the screen (in the case of vertical keystone).

The image may also lean toward one side of the screen (horizontal keystone).

You can prevent keystones by adjusting the projector and screen until they square up.

If keystone occurs, use manual or digital keystone correction to restore the image to its original shape.

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