User Manual

Table Of Contents
Color Management
The simplified goal of color management is to make sure that the image you see on your
computer screen is what your audience sees when they view it on a television, cinema screen,
or mobile device. For such a simple goal, problems arise that you, as the compositor, must
manage. These problems begin with the fact that our eyes see luminance one way, and a
computer display represents luminance differently.
Each capture device records images using a nonlinear tonal curve or gamma curve to
compensate for this difference. Specifically, REC 709 HD gamma curves are designed so that
when shown on HD displays, the images have built-in compensation for the display. The result
is that HD images on HD displays appear normal to us.
Digital cinema cameras have taken the concept of gamma curves further. They use gamma
curves as a way to maximize the bit depth of an image and store a wider dynamic range. Digital
cinema cameras’ gamma curve (often collectively referred to as log gamma), give more
attention to the darker mid-tones where the human eye is most sensitive. This allows them to
save images with brighter highlights and more detail in shadows.
A REC 709 HD gamma curve (left) and a nonlinear, or log gamma, curve (right).
The problem is that these images do not look normal on any monitor. Clips recorded with a log
gamma curve typically have a low contrast, low saturated appearance when viewed on an
sRGB computer display or Rec 709 HD video monitor. This problem is easy to fix using a
LookUp Table, or LUT. A LUT is a form of gamma and color correction applied to the viewer to
normalize how the image is displayed on your screen.
A clip displayed with a nonlinear, log gamma curve (left) and corrected in the viewer using a LUT (right).
All Compositing Is Math
The LUT applied to the viewer only solves the problem in the viewer. Now we come to the
larger problem. The image data is still using a log gamma curve. Fusion, and every other
image-processing application, operates with the assumption that the image data has linear
gamma. The image-processing filters you apply to images use standard math functions, like 1 + 1
= 2. Common operations such as those that add pixels like Brightness, or divide pixels (a.k.a.
“unpremultiply), or composite modes that include multiplication such as “screen,” and many
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