Projector ladder correction is introduced, split and automatic

What is ladder correction?

“Trapezoidal distortion” occurs when the projector is not aligned vertically with the screen, or when the projection screen has a slanted surface. The image produced by one of these misalignments will look trapezoidal rather than square. Distorted images are a distraction that most presenters want to avoid. However, in some cases, there is no other place to put the projector. So, what can you do?

Early projectors did not have ladder correction. Projectors are usually found in fixtures, so furniture and screens can often be moved to fit. As projectors become lighter and more portable, the demand for simpler solutions is growing.

Manual ladder correction

Today, there are two methods of ladder correction, manual and digital. Manual trapezoidal correction is basically the physical adjustment of a projector’s lens so that it projects at a higher or lower Angle than it would on a flat surface. Manual adjustment works well in some cases, but does not eliminate horizontal trapezoidal distortion. The projector also needs to be away from the screen to be effective. Not good enough, you say? Keep reading……

Digital ladder correction

LCD and DLP™ projectors are both digital display devices. Data such as PowerPoint presentations sent to the projector are digitally converted and scaled. By adding special selectable algorithms to scaling, some new projectors are able to change the image before it reaches the projected lens. The result is a square image, even at an Angle. This gives the presenter more flexibility when setting up the projector in a variable environment.

Degree of correction

Projectors can provide different amounts of trapezoidal distortion correction. For vertical (up and down) trapezoidal corrections, some offer a modest 12 degrees, while others offer up to 35 degrees of correction. Some new projectors, such as the latest Hitachi projector lineup, also offer horizontal (side-to-side) trapezoidal correction.

While ladder correction is a convenient feature for road warriors and other portable projector users, it does not produce the desired image quality. Zooming inside the projector produces a slightly distorted image, especially on the sides of the screen. In long-term installation, lens shift is superior to trapezoidal correction.