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8-bit, 10-bit, 32-bit, and more

Just for giggles, here’s what a blue control knob would look like for a 12-bit device:

Starting to see the pattern? The higher the color bit depth, the higher the color precision. A higher color bit depth means more variety, more choices on how much color can be used for each pixel.

Each pixel has more than just one color - each pixel usually has 3 numbers assigned to it - either RGB or something called YUV, which I’m not going to explain here. Each of these values are all the same bit depth - If a camera is an 8-bit recording format, each value for each pixel is an 8-bit number.

Now, 8-bit, 10-bit, and 12-bit color are the industry standards for recording color in a device. The vast majority of cameras use 8-bits for color. If your camera doesn’t mention the color bit depth, it’s using 8-bits per channel. Higher-end cameras use 10-bit, and they make a big deal about using “10-bit precision” in their literature. Only a select few cameras use 12-bits, like the digital cinema camera, the RED ONE.

Software like After Effects and Premiere Pro processes color images using color precision of 8-bits, 16-bits, and a special color bit depth called 32-bit floating point. You’ve probably seen these color modes in After Effects, and you’ve seen the new “32” icons on some of the effects in Premiere Pro CS5.

8-bit processing actually works the same as 8-bit on the camera - each color for each pixel is stored as a value of 0-255. When adjustments to colors are made, they move up one whole number. So, for example, if I had a blue value of 128, and wanted to make a small adjustment, I could change the value to 127 or 129.

To enable more steps, there’s 16-bit color. 16-bit color is used by After Effects and Photoshop, but isn’t in Premiere Pro CS5. This works the same way, except each channel has 32,768 steps to choose from. Any time you drop an 8-bit source into a project using 16-bit color, the 8-bit values are remapped to their relative positions in the new color space. Zero stays zero, and 255 becomes 32768. The midpoint value of 128 in my last example would be mapped to 16384. That’s a whole lot more steps to work with - I can make much more subtle adjustments to the amount of blue in the image. 16-bit color also requires whole “clicks” - You still can’t use a decimal value, like 16384.5 to define a color value.

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