Focus on Technology: Visual Presentation Spaces, Part I Understanding the 468 Rule
Designing presentation facilities can be challenging, but the basic principles are not difficult. Each project and venue comes with its own set of variables and limitations that require some analysis to determine how to create the most optimal conditions.
The key visual element in a presentation facility is the screen. The size of the screen is tied to the size of the room, and changes to one can affect the other. In order to understand how the two are related, it’s important to understand some of the standard ratios involved in the creation of a facility.
The 468 Rule is the basic concept in determining image size in a presentation space. It sets the image size based on the furthest viewer from the image. The image height in a room should be at least 1/4, 1/6, or 1/8 the distance to the furthest viewer, depending on the type of content being viewed.
- 1/8 is for general viewing (i.e. video content with few symbols or text)
- 1/6 is for detailed viewing (i.e. PowerPoint with many symbols and text)
- 1/4 is for inspection viewing (i.e. medical images, maps, artwork, etc.)
For example, in a facility where the furthest row of seats are set at 72 feet from the presentation / front wall, a screen being used primarily for general video content should be 1/8 that distance, or 9 feet tall. Detailed viewing requires 1/6 the distance, or 12 feet. Inspection viewing needs 1/4 the distance – in this case, a screen that is 18 feet tall.
Once the image height is determined the width is set by the aspect ratio of the image content. 4:3(1.33) is a traditional computer display but it is becoming more common for content to be provided in a widescreen format such as 16:9(1.78) or 16:10(1.6). By taking these fixed ratios of the projected content and multiplying by the image height the image width is determined. In the example of a 9-foot tall screen, a standard ratio (4:3) would suggest a 12 foot wide screen (4 x 9 = 36, 36 / 3 = 12). A widescreen ratio of 16:9 would suggest a 16-foot wide screen.
Of course the first compromises often start here. Usually the theoretical image size won’t fit a “standard” screen size from one of the projection screen manufacturers so there has to be an adjustment. Manufacturers do make custom size screens but it costs more and takes longer for delivery, so a “standard” size is often preferable if it does not seriously compromise a project.
Now that the properly sized screen has been found as the best fit for the space, it’s time to focus on where to position the screen in relation to the seats. In the next newsletter we will explore the angles and standards used in creating optimal presentation facility viewing.
Click here for Part II