Apple MA434Z/A User Manual - Page 640

High Color The new highest value in the image. A value of 1 equals no change. aHi A high value control for the alpha channel. ContrastLum The ContrastLum node applies a contrast change on the image, with a smooth falloff on both the low and high ends. You can also move the center of the contrast curve up and down (for example, move it down to make your overall image brighter). Note that this contrast is based on the luminance of the pixel, so it balances red, green, and blue, and you therefore do not shift your hue. So, an image with strong primary colors looks different than an image with the same values in a ContrastRGB node, which evaluates each channel separately. Also note that a roll-off is built into the contrast node, giving you a smooth falloff at the ends of the curve. This is controlled by the softClip parameter. Parameters This node displays the following controls in the Parameters tab: value The contrast value. A higher value means it pushes your RGB values toward 0 and 1. A value of 0 equals no change. A lower value is low contrast. center This is the center of the contrast curve. A lower value is a brighter image. softClip This controls the drop-off of the curve. When increased to 1, you have maximum smoothness of the curve. ContrastRGB The ContrastRGB node applies a contrast curve on each channel individually, so you can tune the channels separately. This differs from the ContrastLum node in that it only changes the pixel value according to its own channel. For a good example of how the functions differ, plug a ColorWheel node into both a ContrastLum and ContrastRGB node. Notice that the ContrastLum node is weighed away from the green values. This also means the ContrastRGB node runs the risk of shifting the hue as you adjust your channels. 640 Chapter 23 Color Correction