AV Police Squad

Back to Basics: Image Size

Flat panel displays offer a lot of advantages over their projector predecessors.

I think it’s fair to say that flat panel installations are outpacing projector installations in conference rooms. They keep on getting bigger, cheaper and better. Plus, you don’t have to worry too much about ambient light in the room or coordinating with congested ceilings. (Why do they always put duct work exactly where you want to put the projector?!) However, any transmissive display image over 100″ is going to be very pricey compared to a projector. So, how do you know when to stay with an LCD display instead of going with a larger image from a projector?

InfoComm has had the 4, 6, 8 rule for as long as I can remember. For “detailed viewing without clues” (drawings, maps, medical), the furthest viewer should be less than 4x the height of the image away from the screen. For “detailed viewing with clues” (presentations, websites, spreadsheets), the furthest viewer should be less than 6x the height of the image away from the screen. For “general viewing” (video, camera), the furthest viewer should be less than 8x the height of the image away from the screen. Part of commissioning a system includes confirming that users will be able to view the tasks at hand easily, so satisfying this rule is important to make sure users aren’t straining or quickly fatiguing their eyes when looking at the system display.

Using the 4, 6, 8 rule, a 90″ display in a typical conference room setting will only support a 24′ deep room. A 90″ display is roughly 4′ high. Typical conference rooms need to read spreadsheets on the displays (6x, “detailed viewing with clues”). So, 6x the height of the image translates to the furthest viewer being less than 24′ away. Therefore, if there is less than 24′ to the furthest viewer, a 90″ display will meet this criterion. If there is more than 24′, we should really go with a projector. A 90″ display solution will beat this rule in a lot of conference spaces…but certainly not all. When do you compromise?

Certainly for video conferencing solutions, if you can get close to the image size you need with an LCD, you’ll be much better off. Cameras love ambient light. Projectors hate it, as it washes out the image. It is very difficult to install an effective video conference room with projectors.

Boardrooms with panoramic views of the city are also a good reason to stick with LCDs. Even if they paid tens of thousands of dollars for blackout window treatments to allow for proper ambient lighting on projector screens…if you think the executives are going to cover up the view they are paying outlandish rent for to view some underlings spreadsheet, you’re crazier than a newbie tech taking on an elementary school PA system service visit. I’ve seen engineers install $50,000 projectors in boardrooms to deliver a beautiful, bright image with the shades down. Despite this effort, executives still wheeled in $4,000 consumer-grade 80″ LCD displays so they could keep the windows up. You can lead a horse to water, I suppose.

When price is critical, an LCD will typically be less expensive over all. Taking into account projection screens, mounts, running power to projectors and screens, cost of lamps/changing filters over a lifetime, it is easy to see how the true cost of ownership of projectors quickly creeps past that of flat panel displays.

Offices with a younger crowd might not need as large a screen. The 4, 6, 8 rule was based on people without perfect vision. A younger office may have better vision. If most of the users have 20-15 vision due to medical advances, image size becomes less critical.

The point is, there are plenty of reasons to break the 4, 6, 8 rule and still satisfy all your client’s needs, as long as it’s done on purpose. Flat panel displays offer a lot of advantages over their projector predecessors. However, we should be aware of what we are risking when selecting a smaller screen. The Dalai Lama XIV said it best, “Know the rules well, so you can break them effectively.”

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