AV Police Squad

Why So Mean, Videowall?

From the files of the AV Police Squad
Videowall

There were five minutes left before the client showed off the new videowall to the higher-ups. We had been color balancing for a few hours at this point in front of all the displays, and they looked pretty good. After a few hours, though, my eyes were starting to play tricks on me. You know those pulsing purple squares you see for a few seconds after someone uses a camera with a flash? Imagine a flash that was 8 feet tall and 15 feet wide…and that just stayed on…and that someone was paying you to stare directly into for hours. I digress. We had a job to do, and I thought we did it pretty well. I wasn’t concerned at all when I saw the client coming down the hall.

“Wow. I thought you said you guys were done.”

“We are.”

“But these two displays are way off.”

I had no idea what he was talking about. We had a full white image up, and it looked good. The problem was he was looking at the wall from the side. I was looking at the wall straight on. We were both right…or both wrong. Either way, we still had work to do. The client was not happy.

Some videowall monitors come with a USB colorimeter to automatically set the color to a standard across the entire wall. This is great. However, other manufacturers recommend setting the wall up by eye.

The problem is: whose eye?

I might see colors a bit differently, or have a lower tolerance for color mismatches than my client. Afterimage (where a bright light leaves a lingering image in your eye) is also a real problem when setting up several bright monitors for a long time by eye. Additionally, each manufacturer takes a different approach to color balancing. Some give you RGB color controls. Some only provide color presets and let you tweak the brightness and contrast of each preset. Some give you an insane amount of color controls that are just overwhelming. If the display on the right looks “a little redder” than its neighbor, do you just drop the red level, or do you adjust the backlight, select the “Video Game” color preset, increase the saturation and then drop the contrast?

Back to the story, what do you do when it looks good from the front of the wall, but it is off from the side? Without a colorimeter or some other instrument that interfaces with the displays to automatically and scientifically set the color for the displays, how do you know when they are color balanced?

At AVR, we have default tolerances of +/- 10 nits for brightness and +/- 250⁰ Kelvin for color temperature across the videowall. That appears to meet the needs of most of our clients, and it is easy enough to confirm that a videowall is within tolerance. The problems start when your displays fall outside that tolerance. How do you fix it? Also, does the side-view tolerance follow the front tolerance on all displays? What have you come across?

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