Grain NodeThe Grain node enables you to simulate the effects of film grain. The Library menu offers presets for several popular film stocks. If desired, however, a number of adjustment parameters are available to provide precise control over the characteristics of the grain added to the input image. This is particularly useful for visually matching grain to different images for a later composite. The grain node works on the Red, Green, and/or Blue channels by assigning a value to each pixel, based on a Gaussian distribution. These values are then scaled according to the node controls and added back into the input image. The overall visual effect will depend on the parameter specifications and the brightness of the input image. The principal differences between the Grain node and the Noise node are the library of presets offered in the Grain node, the fact that the RGB channels can be controlled independently in the Grain node, and the way the grain patterns are distributed (Noise uses a constant distribution). In general, a Gaussian distribution will provide a better match for film grain. Matching Grain PatternsStart by selecting a specific type of film stock, if applicable, from the Library menu in the Grain tab. The other Grain node parameters will default to settings optimized for the selected film stock. If the result is not as exact a match as desired, follow these steps to visually match the node output to an existing grain pattern:
Grain Parameter Tab![]() LibraryThe Library menu enables you to select preset values optimized for various film stocks, as well as a Custom option to set the parameters manually by matching grain patterns visually: SeedThe Seed value is used to generate a sequence of random numbers for the grain operation. Varying the Seed parameter will generate a different grain pattern for each frame. By default, this parameter has been animated using the $F variable--which represents the current frame number--to create a new value for every frame. (Note that the STED button is in its active state, which indicates an animated parameter.) To change this value, check the Expressions box and type in a new expression, or Alt-click the STED button to deactivate it and type in any integer. SaturationThe Saturation parameter controls the color saturation of the grain. A value of 0 will result in monochrome grain and a value of 1 will result in completely independent red, green, and blue grain. Control Image ParametersThe Control Action and Control Channel menus enable you to specify how an optional control image input will govern the node operation, as explained in "Using Control Images with Filter Nodes ." Custom Parameter TabThe Custom tab provides parameters for making precise adjustments to the grain pattern produced. The Size, Amount, and Falloff of the grain can be controlled for each channel (RGB) independently. ![]() Size (Red, Green, Blue)The Size parameters set the average pixel size of the grain added to the image in the Red, Green, and Blue channels. The precise size of each individual kernel will vary. Amount (Red, Green, Blue)The Amount parameters can be used to increase or decrease the apparent amount of grain added to the image in the Red, Green, and Blue channels. Larger values will result in a more substantial addition or subtraction from each pixel in the input image, leading to the appearance of more grain. Falloff (Red, Green, Blue)The Falloff parameters enable you to increase or decrease the concentration of grain based on the brightness of the imagery in the Red, Green, and Blue channels. Higher falloff levels reduce the prominence of grain in darker areas of an image and increase the prominence of grain in the brighter areas. |