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A footage item with premultiplied channels (top) appears with a black halo when interpreted as Straight-Unmatted (bottom left). When the footage item is interpreted as Premultiplied-Matted With Color and the background color is specified as black, the halo does not appear (bottom right).
See also“About straight and premultiplied channels” on page 253
Set the alpha channel interpretation for a footage item 1 In the Project panel, select a footage item.
2 Choose File Interpret Footage Main.
3 If you want to switch the opaque and transparent areas of the image, select Invert Alpha.
4 In the Alpha section, select an interpretation method:
Guess Attempts to determine the type of channels used in the image. If After Effects cannot guess confidently, it beeps.
Ignore Disregards transparency information contained in alpha channel.
Straight - Unmatted Interprets the channels as straight.
Premultiplied - Matted With Color Interprets channels as premultiplied. Use the eyedropper or color picker to specify the color of the background with which the channels were premultiplied.
Set the default alpha channel preferences 1 Choose Edit Preferences Import (Windows) or After Effects Preferences Import (Mac OS).
2 Choose options from the Interpret Unlabeled Alpha As menu. The options in this menu are similar to the options in the Interpret Footage dialog box. Ask User specifies that the Interpret Footage dialog box opens each time a footage item with an unlabeled alpha channel is imported.
Setting the composition frame rate to twice the rate of the output format causes After Effects to display each field of interlaced source footage as its own, separate frame in the Composition panel. This process lets you set keyframes on individual fields and gain precision when animating masks.
When you render a movie for final output, you can choose to use the composition frame rate or another frame rate.
This is useful when you are using the same composition to create output for multiple media.
Each motion-footage item in a composition can also have its own frame rate. The relationship between the footageitem frame rate and the composition frame rate determines how smoothly the layer plays. For example, if the footage-item frame rate is 30 fps and the composition frame rate is 30 fps, then whenever the composition advances one frame, the next frame from the footage item is displayed. If the footage-item frame rate is 15 fps and the composition frame rate is 30 fps, then each frame of the footage item appears in two successive frames of the composition.
(This assumes, of course, the simple case in which no time stretching or frame blending has been applied to the layer.) Ideally, use source footage that matches the final output frame rate. This way, After Effects renders each frame, and the final output does not omit or duplicate frames. If, however, the source footage has a frame rate slightly different from what you want to output to (for example, 30-fps footage and 29.97-fps final output), you can make the footage frame rate match the composition frame rate by conforming it.
Conforming the frame rate of a footage item does not alter the original file, only the reference that After Effects uses.
When conforming, After Effects changes the internal duration of frames but not the frame content. Afterward, the footage plays back at a different speed. For example, if you conform the frame rate from 15 fps to 30 fps, the footage plays back twice as fast. In most cases, conform the frame rate only when the difference between the footage frame rate and the output frame rate is small.
Note: Conforming can change the synchronization of visual footage that has an audio track, because changing the frame rate changes the duration of the video but leaves the audio unchanged. If you want to stretch both audio and video, use the Time Stretch command. (See “Time-stretch a layer” on page 218.) Keyframes applied to the source footage remain at their original locations (which retains their synchronization within the composition but not the visual content of the layer). You may need to adjust keyframe locations after conforming a footage item.
You can change the frame rate for any movie or sequence of still images. For example, you can import a sequence of ten still images and specify a frame rate for that footage item of 5 frames per second (fps); this sequence would then have a duration of two seconds when used in a composition.
Note: If you remove 3:2 pulldown from interlaced video footage, After Effects automatically sets the frame rate of the resulting footage item to four-fifths of the original frame rate. When removing 3:2 pulldown from NTSC video, the resulting frame rate is 24 fps.
The composition’s frame rate should match that of the final output format. In most cases, you can simply choose a composition settings preset. In contrast, set the frame rate for each footage item to that of the original source footage.
See also “Work with render settings” on page 597 “Converting movies” on page 630
Change frame rate for a composition 1 Choose Composition Composition Settings.
2 Do one of the following:
• Choose a composition settings preset from the Preset menu.
• Set the Frame Rate value.
Note: Jeff Almasol provides a script to set the frame rate and duration of the current composition and all compositions nested within it: www.adobe.com/go/learn_ae_jeffcompsetter.
Change pixel aspect ratio Pixel aspect ratio is the ratio of width to height of one pixel in an image. Frame aspect ratio is the ratio of width to height of the frame dimensions of an image.
A 4:3 frame aspect ratio (left), and a wider 16:9 frame aspect ratio (right) Most computer monitors use square pixels, but many video formats—including ITU-R 601 (D1) and DV—use nonsquare rectangular pixels.
Some video formats output the same frame aspect ratio but use a different pixel aspect ratio. For example, some NTSC digitizers produce a 4:3 frame aspect ratio, with square pixels (1.0 pixel aspect ratio), and a resolution of 640 x 480. D1 NTSC produces the same 4:3 frame aspect ratio but uses nonsquare pixels (0.9 pixel aspect ratio) and a resolution of 720 x 486. D1 pixels, which are always nonsquare, are vertically oriented in systems producing NTSC video and horizontally oriented in systems producing PAL video.
If you display nonsquare pixels on a square-pixel monitor without alteration, images and motion appear distorted;
for example, circles distort into ellipses. However, when displayed on a broadcast monitor, the images are correct.
When you import D1 NTSC or DV source footage into After Effects, the image looks slightly wider than it does on a D1 or DV system. (D1 PAL footage looks slightly narrower.) The opposite occurs when you import anamorphic footage using D1/DV NTSC Widescreen or D1/DV PAL Widescreen. Widescreen video formats have a frame aspect ratio of 16:9.
Note: To preview non-square pixels on a computer monitor, click the Toggle Pixel Aspect Ratio Correction button at the bottom of the Composition panel.
AFTER EFFECTS CS3 56 User Guide
If a footage item uses nonsquare pixels, After Effects displays the pixel aspect ratio next to the footage item’s thumbnail image in the Project panel. You can change the pixel aspect ratio interpretation for individual footage items in the Interpret Footage dialog box. By ensuring that all footage items are interpreted correctly, you can combine footage items with different pixel aspect ratios in the same composition.
After Effects reads and writes pixel aspect ratios directly from QuickTime movies. For example, if you import a movie captured as widescreen (16:9 DV), After Effects automatically tags it correctly. Similarly, AVI and PSD files contain information that explicitly indicates the pixel aspect ratio of the images.
If a footage item does not contain information that explicitly indicates the image’s pixel aspect ratio, After Effects uses the dimensions of the footage item’s frame to make a guess. When you import a footage item with either the D1 resolution of 720 x 486 or the DV resolution of 720 x 480, After Effects automatically interprets that footage item as D1/DV NTSC. When you import a footage item with the D1 or DV resolution of 720 x 576, After Effects automatically interprets that footage item as D1/DV PAL. However, you can make sure that all files are interpreted correctly by looking in the Project panel or the Interpret Footage dialog box.
Note: Make sure to reset the pixel aspect ratio to Square Pixels when you import a square-pixel file that happens to have a D1 or DV resolution—for example, a non-DV image that happens to have a resolution of 720 x 480.
The composition’s pixels aspect ratio setting should match that of the final output format. In most cases, you can simply choose a composition settings preset. In contrast, set the pixel aspect ratio for each footage item to that of the original source footage.
See also “Common pixel aspect ratios” on page 57
Change pixel aspect ratio for a composition 1 Choose Composition Composition Settings.
2 Do one of the following:
• Choose a composition settings preset from the Preset menu.
• Choose a value from the Pixel Aspect Ratio menu.
Use square-pixel footage for output to D1/DV NTSC If you intend to create a movie for the D1 output format, use the D1 NTSC or D1 PAL composition settings preset.
The correct pixel aspect ratio for D1 NTSC or D1 PAL is chosen automatically when you choose the corresponding composition settings preset.
1 Prepare square-pixel footage that fills the entire frame for any of the following final output formats:
DV NTSC Create and save it at a 720 x 534 frame size.
D1 NTSC Create and save it at a 720 x 540 frame size.
D1/DV PAL Create and save it at a 768 x 576 frame size.
4 Choose Composition New Composition, and then do one of the following:
• If your final output is DV, choose NTSC DV, 720 x 480 for Preset, and D1/DV NTSC (0.9) for Pixel Aspect Ratio.
• If your final output is D1, choose NTSC D1, 720 x 486 for Preset, and D1/DV NTSC (0.9) for Pixel Aspect Ratio.
5 Select your other composition settings as desired, and then click OK.
6 Add your footage to the new composition.
7 Select the layer containing the square-pixel footage and apply the Fit To Comp command: press Ctrl+Alt+F (Windows) or Command+Option+F (Mac OS).
Note: If your footage was created and saved at a frame size other than those noted in step 1, skip step 7.
See also“Change pixel aspect ratio” on page 55
Working with footage items Organize and view items in the Project panel Compositions and footage items are listed in the Project panel. Unlike items in the Timeline panel and Effect Controls panel, the order of items in the Project panel has no influence on the appearance of the movies that you create. This means that you can organize footage items and compositions however you like, including organizing them using folders. Solids are automatically placed in the Solids folder.
Folders that you create in the Project panel exist only in the Project panel. You can expand a folder to reveal its contents, and put folders inside other folders. To move a file or folder to the top level of the Project panel, drag it to the gray information area at the top of the panel.
You can use the File Collect Files command to gather copies of all files in a project into a single folder.
See also “Collect files in one location” on page 594 “Work with color labels” on page 149 “Shortcuts for working with projects” on page 639 Show information for items
• To show information about a footage item or composition, select it in the Project panel. Information is displayed at the top of the Project panel next to the thumbnail image.
• To show the file creator ID for a footage item, Alt-click (Windows) or Option-click (Mac OS) it in the Project panel.
Rename and sort items
• To rename a composition, footage item, or folder, select it in the Project panel, press Enter (Windows) or Return (Mac OS), type the new name, and then press Enter or Return again.
Note: The names of items in the Project panel can be no more than 31 characters long. The same is true for names of layers, effects, and property groups in the Timeline panel and Effect Controls panel.
• To rename the Comments column, right-click (Windows) or Control-click (Mac OS) the column heading and choose Rename This.
You can use the Comments column to create a custom sorting option. Rename the column, enter corresponding information for each item (for example, camera number), and then sort by that column.
• To sort items by entries in any column, click the column name in the Project panel.
• To duplicate or copy an item in the Project panel, select it and choose Edit Duplicate or Edit Copy.
• To copy a footage item to Windows Explorer (Windows) or the Finder (Mac OS), drag the footage item from the Project panel to the desktop.
Find and view items in the Project panel
• To find items in the Project panel, choose File Find, or click the Find button at the bottom left of the panel.
Select Find Missing Footage to locate all footage items that refer to a file that has been moved, deleted, or renamed.
• To find the next item that matches the most recently used search criteria, Alt-click (Windows) or Option-click (Mac OS) the Find button.
Working with footage items in the Footage panel
When you double-click a movie in the Project panel, it opens by default in the Footage panel or in a player window: