5.5

83Motion User Guide
The following controls let you modify source media in the Media list. Modifying source
media modifies all layers in a project linked to that media.
Note: The parameters described below do not apply to Photoshop files imported as
separate layers. And PDF files with transparent backgrounds do not have the Alpha Type or
Invert Alpha parameters.
• Alpha Type: A pop-up menu to set how Motion deals with alpha channels in the media
item. An alpha channel contains information about areas of transparency in the image
or movie. When you import an image file or QuickTime movie that has an alpha channel,
its alpha channel is immediately recognized by Motion. There are several different ways
to embed alpha channel information into files, which correspond to the options in this
menu. Motion assigns an option based on an analysis of the object when it’s imported,
but you can override the default if necessary, by choosing any of the following:
• None/Ignore: The default setting for objects with no alpha channel. This option also
allows you to ignore an object’s alpha channel, so the entire object appears solid.
• Straight: These alpha channels are kept separate from the red, green, and blue
channels of an image. Media files using straight alpha channels appear 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 can appear distorted until the clip is used in a composition. If
Straight is chosen but you see a black, white, or color fringe around the object,
this parameter is incorrectly set and should be changed to a Premultiplied option,
depending on the color of the fringe.
• Premultiplied–Black: This type of alpha channel is multiplied with the clip’s red,
green, and blue channels. As a result, objects with premultiplied alpha channels
look correct, even with translucent lighting effects, because the entire image is
precomposited against a solid color. This option interprets alpha channels that are
precomposited against black.
• Premultiplied–White: This option interprets alpha channels that are precomposited
against white.
• Guess Alpha Type: This option forces Motion to analyze the file in an attempt to
figure out what kind of alpha channel is used. If you’re unsure, use this setting.
• Color Space Override: If the color space metadata for a video clip is missing or
incorrect, use this pop-up menu to change the media’s color profile so that Motion
processes and displays the selected video correctly. The options vary depending on the
selected file. Rec. 601, Rec. 709, and Rec. 2020, Rec. 2020 HLG, and Rec. 2020 PQ are
available for most files; sRGB IEC61966-2.1 and Adobe RGB are available for still images.
See Intro to wide color gamut and HDR in Motion.
Tip: It’s best to set the correct color space for your media before attempting any
color correction.
• Invert Alpha: A checkbox that, when selected, inverts an alpha channel that is
incorrectly generated in reverse. Ordinarily, an alpha channel is a grayscale channel,
where white represents areas of 100 percent opacity (solid), gray regions represent
translucent areas, and black represents 0 percent opacity (transparent).