THORBURN ASSOCIATES

Acoustic and Technology Consultants

Designing Quality Environments

Front vs. Rear Projection -- Questions and Answers

From an entertainment point of view there is probably nothing more impressive than going to a first run cinema (front projection) and being enveloped by the large screen and catchy plot. That's great if the purpose is for entertainment or large scale audiences. However, if the purpose is to explain a project topic or concept, a different system may be desired. When we are giving lectures or presentations we tend to move around and interact with our slides and graphics. If we use front projection we often disrupt or block part of the image. If rear projection is used we can interact and discuss the image without causing shadows. The solution as to which is best is determined by how the client will make presentations.

The following list describes the issues we discuss to determine which system is most appropriate for a project.

Front Projection

Advantages

• Allows a much bigger image.
• Wide viewing angle.
• Allows for Keystone correction (where the top of the image is wider than the bottom of the image, see picture below).

Disadvantages

• The room lighting for front projection must be carefully designed. The image you view, when front projection is used, consists of light from the projector reflected off the screen. This also means any light in the room will also be reflected off the screen back to you, washing out the image (this is why a cinema is generally very, very dark).

• Projection equipment is often located in the same room as the screen and unless carefully coordinated creates a new source of noise, glare, distraction, etc.

Rear Projection

Advantages

• Allows for easy interaction with the projected image.
• Good for long, narrow rooms such as conference rooms.
• Can be viewed in a room with normal illumination.
• Excellent for taking notes and command center types of situations where individuals move around and are doing other activities.
• Generally provides a cleaner looking system installation appearance.

Disadvantages

• Screen size is limited to the size of transportable glass.
• Space is required behind the projection screen. However, this space can be utilized as the audiovisual system equipment room. The use of mirrors can further reduce the depth requirements of the room.
• Rear projection systems are generally a little more expensive. Rear projection screens are slightly more expensive than front projection roll down screens and the additional cost of the square footage required for the rear projection room can be an issue.

As you can see there are advantages and disadvantages to both systems and both are very effective when used properly.

The key is to evaluate your clients' needs (both current and future) and select the system that best meets those needs.

© Thorburn Associates, Spring 1994.

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