Copyright 2011 SanDevices, LLC
Carmel, IN 46032
Why do I need 12-bit Pixels?
I'm going to try not to bore you here. If you've worked with standard incandescent 'mini' strings and standard LED strings in the past, you've probably noticed that they don't behave at all alike when you dim them. That's because incandescent lights become much less efficient as they are dimmed, in other words the amount of light given off drops off a lot faster than the amount of current being sent to them. Incandescent bulbs are non-linear. LEDs, on the other hand, are very linear, the amount of light they give off varies directly with the current through them. So if LEDs are linear and incandescents aren't, why do incandescent's look 'nicer' when dimming? Well, it's because our eyes aren't linear either, and it just so happens that our eyes are non-linear in the opposite of the way that incandescents are non-linear. Our eyes are more sensitive to changes in light level of very dim lights, and pretty insensitive to changes of bright lights.

The way it happens to work out is that the non-linearity of incandescent bulbs and the non-linearity of the human eye essentially cancel each other out, and the result is that as we go from 0 to 100% intensity on an incandescent bulb it appears as a nice smooth transition to the human eye, whereas the linear dimming of an LED light appears very non-linear to the eye, it seems to jump from off to a pretty bright value right away.

And that's the reason we need 4,096 dimming levels that the 12-bit pixels give us. We only use 256 of them, because the DMX standard only supports 256 levels. But what we can do is pick which 256 of the 4,096 available levels that we'll use, and we pick them in such a way that our dimming steps are very small toward the dim end of the range, and gradually become larger as we get brighter.

This process is called Gamma Correction, and what we are essentially doing is making the linear LED appear to be non-linear, in a way that makes it's dimming curve close to that of an incandescent bulb. Not only is it more pleasing to the eye, but in a display with both RGB pixels and incandescent minis, both types of lights will have the same dimming curve.

Another benefit of 12-bit pixels and gamma correction is if we want to assemble a large grid or matrix of pixels, and actually use it to display still or video images. Yes it can be done, the technology is just like that used in the 'jumbo' video displays at stadiums. Without gamma correction however, images appear to be washed out. With gamma correction it's possible to display vivid lifelike images on an RGB pixel array.


SanDevices: The Pixel Project
12-Bit Pixel Technology
We Turn Lights into Magic