Adobe After Effects CS4 - Manual (Page 295)

289 USING AFTER EFFECTS CS4
Color
Last updated 12/21/2009
More Help topics
“ Color models and color spaces ” on page 281
“ Color depth and high dynamic range color ” on page 274
Linearize working space and enable linear blending
If you have enabled color management (by specifying a working color space), you can perform all color operations in
linear light by linearizing the working color space. A linearized color space uses the same primaries and white point as
the nonlinear version; the tone response curve for the linearized color space is just a straight line. (See “
Gamma and
tone response ” on page 282.)
If you have not enabled color management, you can still perform blending operations using a gamma of 1.0.
By performing operations in a linear color space, you can prevent certain edge and halo artifacts, such as the fringing
that appears when high-contrast, saturated colors are blended together. Many color operations benefit from working
in a linear color space, including those operations involved in image resampling, blending between layers with
blending modes, motion blur, and anti-aliasing.
If you want to use a linearized working color space, do so when you set up the project, instead of switching later.
Otherwise, colors chosen in the color picker will change when you switch to a linear working color space, because
colors inside After Effects are interpreted to be in the working color space.
Note: A linearized working color space works best with higher color depths—16 bpc and 32 bpc—and is not recommended
for 8-bpc color.
❖ Choose File > Project Settings, and do one of the following:
• To linearize the working color space, choose Linearize Working Space.
• To blend colors in a linear color space, choose Blend Colors Using 1.0 Gamma. This option affects only blending
between layers. The result is that opacity fades, motion blur, and other features that rely on blending modes are
affected.
More Help topics
“ Blending modes and layer styles ” on page 171
Additional resources about linear color spaces and linear blending
Stu Maschwitz’s ProLost blog has several posts that are useful for learning about how, when, and why to work in a
linear color space versus a non-linear color space. In
this post , Stu summarizes the reasons and techniques for working
in a linear color space and using linear blending.
On the ProVideo Coalition website , Mark Christiansen provides some examples of the results of enabling linear
blending, as well as explaining a little more what linear blending means.
Interpret a footage item by assigning an input color profile
You control color management for each footage item using the Interpret Footage dialog box.
The input color profile determines what calculations are performed when converting the colors of a footage item into
the working color space for the project. If a working space has not been set—that is, if color management is not on for
the project—then you cannot assign an input color profile.