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other compositing tasks assume that 1 + 1 always equals 2. In other words, if you perform an
operation that doubles the amount of brightness, then every pixel should be twice as bright.
However, if you are starting with a nonlinear gamma curve, pixels are not being adjusted
linearly, so some pixels might end up 1.2 x as bright, 1.7 x as bright, or 2.4 x as bright. Now the
math is 1 + 1 = 3. The further your images are from linear gamma, the more pronounced the math
error. A REC 709 HD clip shows less error than a log gamma clip from a digital cinema camera.
However, an error is still an error, and the more compositing operations you perform on the
image, the more the error is compounded.
You can see a more practical example when you apply filtering effects, such as a blur, to an
image with any gamma setting. The image probably looks fine. However, if you convert the
image to a linear gamma first and then apply the blur, the images (especially those with
extremely bright areas) are processed with greater accuracy, and you should notice a different
and superior result.
The answer to these problems is to manage your color before compositing.
Introducing Color Management in Fusion
Images loaded into Fusion by default are not color managed. The image is displayed directly
from the file to the viewer without any interpretation or conversion. However, Fusion includes
nodes that convert the output of each image to linear gamma at the beginning of your
composite. The same nodes can convert from linear back to your desired output gamma at the
end of your composite, just prior to the Saver or MediaOut node.
A log clip converted to linear and then converted for output.
To manually set up a linear gamma workflow in Fusion:
1 Use a Gamut or CineonLog node after all MediaIn or Loader nodes to convert them
to linear.
2 Apply a GAMUT View LUT to the viewers to correct the display of a linear image to
sRGB or Rec 709.
3 Before a Saver or MediaOut node, insert a Gamut or CineonLog node to convert from
linear to your target output format.
Converting to Linear Gamma
Whether an image comes from the Edit page in DaVinci Resolve, or from a Loader in Fusion
Studio, the color and gamma are read directly into Fusion, with no modification. For some
simple operations on sRGB or Rec 709 clips, this may be fine, but it’s not always the ideal way
to work, especially for log-encoded media. The ideal way to work with log-encoded media is to
convert images to linear gamma, since the majority of image-processing operations in Fusion
expect gamma to be linear and will produce superior results.
Chapter – 68 Managing Color for Visual Effects 1370