Angles Of Reflection

The start of a new year is as good a time as any to look inward to question the assumptions we seldom take the time to challenge.  In our case, that means pulling back for a moment to cover a few projection screen basics that we often take for granted, regardless of whether or not the actual information has ever been provided.  Even if you think you know the answer already, I think it is relevant to stop and ask:

What is a Projection Screen, Anyway?

The fundamental purpose of a projection screen is to support the viewing of projected images.  This is not the full answer, obviously, but it is at the root of every discussion we are likely to have on the topic of screens.  Expanding on this foundation, the following questions and answers in this document will help us reach a more complete answer.

Are projection screens necessary?

If we define “necessary”, in this context, to mean that the screen is an essential part of a projection system and that every system would fail every time without a screen in place, then the answer would probably be “no”.   This may sound like a cutely provocative answer (and it is, so stay with me here) but the reality is that humanity has filled the world with walls and other surfaces readily available to act as screen alternatives.  In light of this, we may categorize the projection screen as being merely optional.

There is a catch, of course, in that screens are optional for projection in the same sense that roads are optional for driving.  It is absolutely the case that some vehicles are driven without roads just as some projectors are never paired with a screen.  For the majority of users of both, however, their respective complimentary items are absolutely necessary for the realization of peak performance and for simple convenience.

That convenience factor is often the most compelling argument in favor of using a projection screen.  Most walls are incapable of rolling up when not in use, often fail at being portable and are quite prone to attracting picture frames, wall hangings, and other obstructions that interfere with projection.  This is to say nothing of the fact that screens are designed to accommodate the shortcomings of projectors and environments (as will be discussed in the following section) in ways that a common wall cannot reliably be called upon to emulate.

Beyond the convenience is the need for a screen that allows the sophistication of the projector to shine through, as it were.  This is important to professional users in such fields as film and photography, who rely on their projectors and screens to provide an unerringly accurate picture.  It also applies to anyone who uses a projector and screen to display polarized 3D images and, to some extent, anyone who uses a projector at all.

Why are there so many different screen surfaces?

There are numerous obstacles which interfere with the screen’s ability to display projected images and so there are numerous screen types designed to overcome them.  Generally, these obstacles can be collectively understood as arising when the projector is not able to adequately illuminate a screen in order to provide usable images in a given environment.

The influential factors here are the:
* Light output of the projector
* Light levels ambient in the viewing environment
* Size of the screen
* Properties of the screen material

As a screen manufacturer, we have no control over how bright anyone’s projector happens to be.  We likewise have little power to affect the amount of light in the viewing environment.  It is possible for us to alter the size of a screen, however, and that does let us influence the performance of the system somewhat.  If the projector is too dim or the room is too bright, a smaller screen can actually make the image brighter and, therefore, easier to see.  It also makes the image smaller and more difficult to see, which is why we produce a variety of surface types in addition to the different sizes. 

These types are based on an assortment of properties that influence how the screen reflects, diffuses, and even absorbs light.  Through various combinations of these properties, it is possible to do such things as brighten an image, increase contrast and even deflect ambient light.  In other words, projection screens are designed to accommodate an array of requirements and limitations that arise in putting together an actual projection system.

Can anyone even tell the difference between one screen and another during normal use?

Honestly, if all screen materials looked the same under projection, we probably would not bother to make so many different kinds.  Aside from the characteristics we have briefly touched upon already, there are still more variations in screen surfaces that depend upon the materials and techniques used in their construction. 

While it is true that the human eye is remarkably adept at overlooking a variety of irregularities and shortcomings in displays of all kinds, it is also true that it is absolutely possible to distinguish one screen from another, due to these variations.  It is part of what not only sets one brand apart from another but also makes it important to select the right screen for the situation.

-- Adam Teevan
    ateevan@da-lite.com

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