There are various factors most know about when setting up a projection system but the proverbial “devil in the details” often goes overlooked. I’m talking about a projector’s vertical alignment. It is a relatively simple function but it has small elements to it that every installer should be aware of and that goes double for houses of worship. It may be a small matter, but the difference between doing it right and wrong will come with either great rewards or a potentially costly disappointment. This is especially important for Houses of Worship because there are so many different ways a projection system can be installed and there are often more variables at play than an enclosed conference room or home theater. As a person of faith, I want to contribute to your congregation’s success. This is one of those AV veteran moments where a small bit of advice can spare you from buying expensive AV gear you don’t need, while getting the best performance out of the equipment you have (or can realistically afford). This is also a topic that will help enhance you the ability to make wise decisions when buying AV gear whenever an upgrade or new building project is in order. With all that said, saddle up; for the next few minutes we’ve got work to do…
The pitfalls of doing it wrong
Keep in mind that calculating the wrong projection angle can create a multitude of problems for you.
- Keystone effect, is created when the projected image has a trapezoid (trapezium) shape. This is caused when your projected light is hitting the screen surface from too high/low of a vertical angle. Most projectors have a keystone adjuster to correct this but any projector without this feature should only be used in-line with the screen.*Tip, make sure the projector you install can handle the angle of projection you want to achieve.
- Hot-spotting and glare, is when a bright spot or glare appears in your projected image. It typically occurs with higher gain (more reflective) and specialized ambient light rejecting (ALR) projection surfaces. This is often the cause of off-axis projection or trying to use a short-throw (ST) projector with an ALR material. Albeit there are a few exceptions, most ALR materials are not designed for use with “ST”-projectors. Specialty materials always present the greatest risk of occurrence so it is best to check with the manufacturer if ever you have a doubt. *Tip, make sure that your screen material and projector are compatible with one-another; they don’t always get along with one another.
- Off-axis light loss, is when a specialty reflective material such as ALR is used with either too steep of a projection angle or the entire screen and projector installation is not properly aligned with the audience’s eye level. *Tip, matte white materials are best when you have good light control and the projector has good contrast performance. ALR materials are best when there is a lot of ambient light but they come with their own limitations.
Adjusting Your Vertical Angle
On a projector, there is typically a feature known as vertical lens shift. This is the projector’s ability to shift an image upward or downward from a projector’s static position without need of physically moving the projector itself. Depending on whether you are ceiling-mounting your projector to shoot down on a screen from the front, or “table-top” positioning from in front or behind the screen, will determine the degree of “vertical adjustment” required from your projector. For high ceilings, a projector with up to 3-times the screen height is required. For in-line imaging typically from a table top or low ceiling installation, a projector that can only adjust up to ½ the screen height may likely be the ideal solution.
*Tip, there are times when you will be able to actually tilt the screen itself to accommodate the projection angle you have. This is often practiced with the angular-reflective “ALR” screen materials.
Whatever your requirements are, always make sure that the desired “sweet spot” of optimal projector screen performance will encompass your entire viewing audience. Ambient light rejecting screens are great but they may not be as ideally suited to your large venue presentation as a white screen would be. Either way, always have a good handle on what your projector’s vertical angle is and what angle of projection your screen can handle. If you do it right, you’ll appreciate the results, your congregation will be grateful for a beautiful display and the cost of all this enjoyment should be less than what you may have expected.
Dave Rodgers is the Marketing Manager for Elite Screens Inc.
For more information, please visit www.elitescreens.com.