AdjustmentsThe Adjustments shader allows an artist to adjust the color levels of his rendered image. The effects listed below are identical to those of several popular packages including Adobe PhotoShopTM and Adobe AfterEffectsTM.
In the render dialogue box, choose mental ray for the rendering type.
Click on Options to get the mental ray options dialogue.
In the output shaders box, select the Adjustments shader, and edit its parameters.
Brightness / Contrast
Brightness adjusts the overall brightness of the color. Negative values make the color darker, positive values make the color brighter.
Contrast adjusts the variation of brightness in an image. Negative values shift the colors towards a neutral gray, while positive values make brights brighter, and darks darker.
Hue / Saturation
Hue changes color in an image; greens can become yellows, reds can become blues. The value specified here is the number of degrees to rotate on the color wheel.
Saturation adjusts the "purity" of a color. Negative values mix in grays, making pastels and lowering the colors' saturation, while positive values remove grays and raise the saturation.
Very similar to Brightness, Lightness adjusts the overall lightness of a color, but uses a slightly different technique. Negative values bring the color to black, positive values bring the color to white.
Levels allows the artist to adjust the overall lighting levels of his image, darkening or lightening shadows and highlights.
Each of the RGB channels for each pixel is changed in the following way: values between Input Low and Input High are remapped to a proportional value between Output Low and Output High. Values below Input Low are remapped to Output Low, and values above Input High are remapped to Output High.
Input Shift will gamma correct the color; a value here of 1.0 corresponds to no gamma correction.
Region controls where the color adjustments will take effect. The two choices are Entire Image, causing all of the image to be adjusted, or Specific Objects, where only those objects chosen in the Specific Objects box will have their color adjusted.