User Manual

Controls Tab
The Controls tab includes all the parameters for modifying the appearance of the film grain.
Complexity
The Complexity setting indicates the number of “layers” of grain applied to the image. With a
complexity of 1, only one grain layer is calculated and applied to the image. When complexity is
set to 4, the node calculates four separate grain layers and applies the mean combined result of
each pass to the final image. Higher complexities produce visually more sophisticated results,
without the apparent regularity often perceivable in digitally-produced grain.
Alpha Multiply
When the Alpha Multiply checkbox is enabled, the Film Grain node multiplies its results by the
source image’s Alpha channel. This is necessary when working with post-multiplied images to
ensure that the grain does not affect areas of the image where the Alpha is 0.0 (transparent).
NOTE: Since it is impossible to say what the final value of semitransparent pixels in the
image are until after they are composited with their background, you should avoid
applying log-processed grain to the elements until after they have been composited.
This ensures that the strength of the grain is accurate.
Log Processing
When this checkbox is enabled (default), the grain applied to the image has its intensity applied
nonlinearly to match the grain profile of most film. Roughly speaking, the intensity of the grain
increases exponentially from black to white. When this checkbox is disabled, the grain is
applied uniformly, regardless of the brightness of the affected pixel.
One of the primary features of grain in film is that the appearance of the grain varies radically
with the exposure so that there appears to be minimal grain present in the blacks, with the
amount and deviation of the grain increasing as the pixels exposure increases. In a film
negative, the darkest portions of the developed image appear entirely opaque, and this
obscures the grain. As the negative becomes progressively clearer, more of the grain becomes
evident in the result. Chemical differences in the R, G, B, layer’s response to light also cause
each color component of the film to present a different grain profile, typically with the blue
channel presenting the most significant amount of grain.
As a result, an essential control in the Film Grain node is the Log Processing checkbox, which
should be enabled when matching film, and disabled when working with images that require a
more linear grain response. Having this checkbox enabled closely mimics the results of
preceding the old Grain node with a Linear to Log conversion and following with a Log to Linear
conversion immediately after.
Seed
The Seed slider and Reseed button are presented whenever a Fusion node relies on a random
result. Two nodes with the same seed values produce the same random results. Click on the
Reseed button to randomly select a new seed value, or adjust the slider to select a new seed
value manually.
Chapter – 90 Film Nodes 2020