What is Keystone Correction in Projectors?

What is Keystone Correction in Projectors and How to deal with it?

Keystone effect is normally found while you are projecting on a screen that is not perpendicular to the projector’s projection direction. So as a result, instead of the image appearing like a regular rectangle shaped image, it becomes distorted and trapezoidal due to the difference in the viewing angle. This image will help you understand better than any number of words:


So basically in the case of a projector sitting on a table, the image is actually broader on the top and smaller at the bottom, this giving it a keystone like appearance and hence the name. Now basic geometry will tell you that there are four kinds of keystone issues. Here are they:


You can see that primarily there are two keystone effects, vertical and horizontal. Vertical is somewhat easy to resolve while horizontal is quite difficult. Now keystoning used to be a big issue in photography and cinematography as well like in previous cameras, skyscrapers would appear with their tops broader than they really were. But, we have moved well past in those fields. Same is true for gaming projectors except we still need to know how to deal with it to adjust it when the time comes. Early projectors didn’t have this ability as they were fixed devices that couldn’t be moved and used to project on a single screen. As projectors became portable, the need for keystone correction methods increased. The ability of any projectors to mitigate the keystone effect is given by their degree of correction. It starts off with a few degrees like 7 or 8 for low-end projectors and as price increases, the degree of correction increases as well. It gets better up to 35 degrees in some really good projectors and some even offer horizontal keystone correction up to a few degrees. There are two methods for correcting the keystone effect on projectors. They are:

  1. Manual Keystone correction

Most of the conventional projectors in the market use a manual keystone correction mechanism. It is basically adjusting the lens of the projectors physically so that it can come to terms with the angle of the screen and give us a proportionate projection at the end. So it involves adjusting the lens of the projector by lowering or raising it so that the result would be as if the projector was on a flat surface.

The problem with manual keystone correction is that it cannot be used for horizontal keystone correction. For that you will need digital keystone correction option and that costs extra bucks.

  1. Digital Keystone correction

LCD and DLP projectors are equipped with this function. Each image is digitally converted and scaled by the projector. So, instead of changing the position of the projector to remove the keystone effect, a special algorithm is added to the system to alter the image before it can be projected. The result is that we can enjoy a consistent proportionate image even at an angle. So, a digital keystone correction projector offers much more versatility and flexibility while setting up your projector anywhere.

How does it relate to gaming?

For gaming purposes, keystone effect is not welcoming at all. It distorts the image and the screen appears disproportionate while some icons appear larger, others appear smaller so especially in a game like FIFA or Call of Duty, the effect is very pronounced and it will negatively affect your gaming experience. Especially if you are looking for a portable product, the keystone can a big turn off as we all know how impromptu our gaming scenario can be.

Lens shift or Keystone correction?

But there are downsides to keystone correction as the resulting image is not perfect due to our meddling and it may become distorted at the end. While it is useful for portable purposes, many don’t feel the need for it and a Lens Shift Mechanism is what is preferred especially if it is a long-term installation. But, that is a different ballgame altogether.

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