Apple Motion 3 - Manual (Page 225)

Chapter 2 Creating and Managing Projects 225
Object Media Tab Parameters
When you select an object in the Media tab of the Project pane, the Inspector displays
a Media tab that contains the properties defining how the object appears in Motion.
This includes parameters such as the type of alpha channel used, pixel aspect ratio,
field order, and so on. All of these parameters can be edited, which changes the way
that object is displayed and composited in your project.
While Motion makes an effort to correctly interpret how objects you add to your
project should appear, sometimes it isn’t possible to correctly identify how a source
media file should be treated. Make sure that each object you add to your project has
the correct settings in its Media tab so you can successfully mix and match objects with
different pixel aspect ratios, alpha channel types, and frame rates.
Because Motion is a nondestructive application, changes made to these parameters are
not applied to the source media files on disk. They simply affect how objects are drawn
within Motion.
Object Parameters in the Media Tab
The following parameters let you control the objects in the Media tab, which also
affects all the instances of the object in the project.
Alpha Type: An object’s alpha channel contains information that defines areas of
transparency in the image or movie. When you import a QuickTime movie or an image
file, its alpha channel is immediately recognized by Motion. There are six different ways
to embed alpha channel information into files, which correspond to the four options in
this pop-up menu. Motion automatically assigns one of these options based on an
analysis of the object when it is imported, but you can override this if necessary.
The six commands in this pop-up menu are:
 None/Ignore: The default setting for objects with no alpha channel. This option also
allows you to ignore an object’s existing alpha channel, so that the entire object is
solid.
 Straight: Straight alpha channels are kept completely separate from the red, green,
and blue channels of an image. Media files using straight alpha channels appear
perfectly fine when used in a composition, but they may look odd when viewed in
another application. Translucent effects such as volumetric lighting or lens flares in a
computer-generated image may appear distorted until the clip is used in a
composition. If Straight is chosen, but you see a black, white, or colored fringe
around the object, this parameter is incorrectly set and should be changed to one of
the Premultiplied options, depending on the color of the fringe.