An image on a full color LED sign consists of thousands of individual pixels. Each pixel consists of individual Red, Green and Blue LEDs; the three primary colors for light. Why three? Because the human eye has three types of color receptors. Technically you could mix other colors, but Red Green and Blue provide the widest range of colors to our eyes in the most efficient manner. If this is the case, then why do some manufacturers use more than three LED’s per pixel?
There a many reasons, some technical, others theoretical, and some are driven by marketing needs. In my experience adding a 4th, 5th, or 6th LED to the pixels does not have a large effect on the actual end-user experience.
Technically, you can increase the view-able color range by adding an extra LED like Yellow (you may have seen this advertised in the LED TV market). However, any real visible effect this would have on an LED sign would be minimal. It also requires a bit more power to drive the thousands of extra LED’s.
Most four LED configurations add an extra Red LED to the pixel. This is sometimes marketed as a way to increase the brightness of the LED sign. It doesn't quite work that way, because you cannot drive each of the Red LEDs at the same level. If you did, the sign would be brighter....but also tinted Red.
Some use a four LED pixel configuration because they are not able to provide Virtual Pixel technology without it. This has only added to the somewhat jaded view many have of Virtual Pixels and if they really make a difference or not (Deacon had a great post on VP here). Generally speaking, you don’t want to add unneeded components to an LED sign to produce a technology like Virtual Pixels that can be done without them.
The fact is there is nothing inherently wrong with 4+ LED pixel configurations, but the benefits they provide are not as large as some may claim and the electrical trade off’s are not always great. As I mentioned before, it’s really about the end-user experience and what they will actually get from the technology.
The human eye can physically see a massive number of light wavelengths, but we do not perceive these in exacting measure. Our brain gives us just the right amount of data that we can handle. In my opinion there are far more important items to clarify with a potential sign supplier than the number of LEDs per pixel...this blog is packed full of them!
I hope this post has been informative and helpful. As usual, I welcome ALL constructive comments. Please feel free to comment and add anything I’ve missed, or additional tips you may have regarding this topic. Please visit www.vantageled.com for many other resources, white papers, and of course: Great looking LED Signs!
**All posts/thoughts/writings are strictly the viewpoint of me and me alone and do not reflect nor speak for Vantage LED’s beliefs, attitudes, thoughts, etc. unless specifically stated.