Adobe After Effects CS3 User Manual
Page 245
AFTER EFFECTS CS3
User Guide
240
The gamma value for an entire system—from capture, through production, to display in the viewing environment—
is the product of the gamma values used for each of the phases in the system. This product is not always 1.0, as it
would be if the operations performed for encoding exactly matched (inverted) the operations performed for
decoding. One reason for a system gamma other than 1.0 is that there is often a difference between the lighting
conditions in which a scene is captured and the lighting conditions in which it is viewed. (Consider that you usually
watch a movie in a dim environment, but the scenes aren’t normally shot in a dim environment.)
For example, the device gamma for an HD camera is approximately 1/1.9, and the device gamma for an HD display
is approximately 2.2. Multiplying these values gives a system gamma of approximately 1.15, which is appropriate for
the somewhat dim television viewing conditions of a typical living room. The system gamma for motion picture
production is much higher (approximately 1.5–2.5) to accommodate the darker viewing environment of a movie
theater. The gamma for the film negative is approximately 1/1.7, and the gamma for the projection film is approxi-
mately 3–4.
QuickTime and gamma in non-color-managed projects
After Effects 7.0 and earlier used QuickTime codecs to decode several kinds of media, and the gamma adjustments
performed by QuickTime on Windows were different from the gamma adjustments performed on Mac OS. The
gamma adjustments performed by After Effects CS3 differ from the gamma adjustments performed by these
QuickTime codecs. Gamma adjustments performed by After Effects CS3 on Windows are the same as gamma
adjustments performed by After Effects CS3 on Mac OS. Also, by not using QuickTime codecs, After Effects
preserves over-range values in 32-bpc projects.
Select Match Legacy After Effects QuickTime Gamma Adjustments in the Project Settings dialog box to accomplish
any of the following:
•
Avoid color shifts when working with projects created in After Effects 7.0 or earlier
•
Match the colors in a project created in After Effects 7.0 or earlier
•
Ensure that colors in Composition panel match colors in QuickTime player
The Match Legacy After Effects QuickTime Gamma Adjustments option is selected by default for projects created
in After Effects 7.0 or earlier. You should create new projects without this option selected.
Note: On Mac OS running on a PowerPC processor, QuickTime codecs are used for some formats (including DV, 2vuy,
and v210), whether or not you select Match Legacy After Effects QuickTime Gamma Adjustments. However, selecting
this option does modify the gamma adjustments used so that they match the behavior of After Effects 7.0 and earlier.
Important: Install the most recent updates for After Effects CS3. Versions 8.0.0 and 8.0.1 of After Effects CS3 do not
correctly export data for some QuickTime RGB codecs.
For current and detailed information on issues related to QuickTime Player and gamma adjustments, go to the
Adobe website at
.
Mark Christiansen has a blog post about QuickTime and gamma:
.
See also
“Linearize working space and enable linear blending” on page 244