A Guide to Front Projector Screen Surfaces

Manufacturers have come up with a wide range of projection screen arrays in a vast choice of projection surfaces to suit different presentation media.

This projector screen fabric selection guide focuses on a specific media application, namely that of home theater and home entertainment.

Clearly, there isn't an all purpose projector screen surface that performs efficiently under all home theater conditions.

This is itself should not be an issue in that whatever your requirements and constraints are - ambient light conditions, limited room configuration, budget restrictions, etc., you can always find a high quality projector screen surface that represents an optimum solution to your needs.

This projector screen guide highlights the basic selection criteria one has to consider to identify the right projection screen surface in a front projection setup.

However, prior to discussing these criteria, we thought that it would be beneficial to present a few 'movie screen basics' in view that the same operational principles apply in the home theater.

Movie Screen Basics

It is a fact that at first glance, movie screens look incredibly simple - a big stretched sheet of white fabric. But a deeper inspection would soon reveal that there is a fair amount of technology and design involved in their creation.

Usually, these are made of heavy white vinyl - but there is more. The movie screen surface is categorized by the amount of light it reflects.

There are four main categories of screen surfaces:

Matte white: This represents a surface with less than 5% reflectivity; black is very dark gray to black but the image is not very bright.

Pearlescent: Surface reflectivity is typically 15%; black is dark gray and image is bright, provides best overall contrast.

Silver: 30% reflectivity; black is medium gray and image is very bright, dark colors may seem a little dull.

Glass bead: This represents the surface with the highest level of reflectivity - typically 40%; black appears as light gray and image is usually too bright. Normally, this type of projector screen surface is used only under special conditions.

Pearlescent is probably the most common choice for a typical movie theater. To make a pearlescent or silver screen, a reflective coating is added to the matte white vinyl.

A glass bead screen uses thousands of tiny glass marbles embedded in a transparent coating on the surface of the screen.

Yet surface reflectivity is just one aspect of a movie theater projection screen. As further detailed in the first part of this series of home theater screen selection guides, movie screens are designed not only to present a great picture but also to support the theater sound system. For the purpose, most movie screens have tiny perforations in them to render the screen acoustically transparent. In this manner, the audience will be able to hear speakers placed behind the screen.

In a typical movie theater application, you'll find three speakers behind the screen, located at the far left, center and far right. In the home theater, usually it is only the center speaker that is positioned behind the projector screen - but this mainly depends on the overall projector screen width.

Placing the speakers behind the screen leads to a more realistic sound experience, particularly with the movie dialog. It also leads to an overall surround sound field that better encompasses both the projected movie image and the audience.

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  Selecting the Right Front Projection Screen Surface

There are a number of basic parameters you have to consider to arrive at the right projector screen surface. Projection method, ambient light, display brightness, seating layout, projector placement, and image detail are all important issues to consider when selecting a projector screen.

Equally important is the projection screen maintenance; this is something many fail to think about at the time of purchase but regular projection screen maintenance is important to ensure that your projector screen continues to deliver the very best images years down the line.

Understanding how these issues impact image performance is essential prior to choosing a projector screen surface. Many would argue that most major projection screen manufacturers' websites include easy-to-fill checklists which once completed, would automatically present you with their recommended screen fabric for your application.

This is true and to a certain extent, these checklists and screen calculators render the selection process a straight forward one. Yet we still say that having a proper understanding of the basic projector screen selection criteria is the only way to ensure that you make the right choice.

Projection Screen Surface Selection Criteria

1: Projection Method 

The type of projector screen surface to use is partially dependent on the projection technology of your video projector.

Common technologies in the home theater area include 3-LCD, single and three-chip DLP, and LCoS; LED driven DLP video projectors have also already started to appear.

Each of these technologies handles brightness, contrast and color intensity in a different manner. Hence projection screen manufacturers have developed  specially formulated color corrected screen surfaces that best complement these different imaging technologies.

2: Ambient Light 

Any projected image is at its best when viewed in total darkness - this being so independent of the projector brightness output. However we live in an imperfect world where not everything is under our full control.

Obviously, the first step is to minimize ambient light during a movie, in particular, avoid any stray light falling direct onto the projector screen  as this causes the projected image to washout.

However, selecting a suitable high contrast projection screen surface can still help you enjoy an image with a sufficient contrast even under moderate ambient light levels.

3: Projected Image Brightness 

The brightness output level of your projector is a measure of the projector output power in terms of light intensity. Yet, it is important to realize that the end projected image brightness - or image luminance - is a different issue as brightness falls in proportion to the area of the projected image size.

This means that the bigger your projected image is, the dimmer it will look for a fixed level of projector brightness.  At the same time, it is extremely important that you would not end up with a too bright an image that would be uncomfortable on the eyes - hence the need to match the screen gain with the projector output level, screen size and ambient light. This also means that one cannot proceed with a projection screen purchase in isolation from your video projector.

We discuss this subject in more detail in the third part in this series of Projection Screen Guides.

4: Room Layout 

The Society of Motion Pictures and Television Engineers (SMPTE) recommends that for the best viewing experience, the ideal screen size for home theater use should occupy a 30 degrees field of view in the horizontal plan at the seating position. This in itself limits the seating area in your home theater room. This 30 degrees field of view is necessary for a person to feel immersed into the movie action.

Some projection screen companies recommend limiting the seating area to approximately 30 degrees from either side to the center of the projector screen. These 30 degrees arise not out of the SMPTE recommendations referred to above for home theater viewing but represents the limit beyond which sitting at the extreme sides of the projector screen would be too uncomfortable for normal viewing. It does not represent the ideal seating in the home theater. For more information on viewing distance and home theater seating, please refer to the following guides on our site:

TV Viewing Distance - viewing distance versus screen size

Home Theater Seating - home theater seating layout

However... if your home theater room configuration calls for a wider viewing angle, then you should make use of suitable screen fabric that can maintain adequate image brightness even at extreme viewing angles.

5: Projector Placement 

Projector placement with respect to the projection screen is another important factor to consider when selecting a projection screen surface. The issue mainly arises when making use of a high-gain projection screen; placing your video projector on a floor-stand would require a different type of screen surface than when the projector is ceiling mounted. Why?

6: Projected Image Detail

This is all a matter of whether you are displaying standard or high definition content.

Screen surface is not much of an issue with standard definition video but to fully enjoy the fine image detail supported by today's 1080p high definition video - especially at close viewing distances, you need to ensure that you use a screen with an exceptionally smooth surface.

7: Screen Maintenance 

Hardly considered during a projector screen purchase, yet to get the best performance, the screen surface should be kept clean all the time.

While in general this is not a problem especially in the dedicated home theater room, yet there are situations where the screen surface may be subject to a higher level of airborne debris and dust that may settle on the surface. Worst is the case where the screen surface may be subject to potential soiling or even damage from constant handling.

Under such circumstances, an easy to clean screen surface is a pre-requisite for continued best performance over time.

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Suggested Further Reading/References

Da-Lite Education - Guide to Selecting Front Projector Screens:
http://www.da-lite.com/education/guide.php?page=intro

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