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Chapter 4. Compositions > Choosing Composition Settings

Choosing Composition Settings

Because compositions describe how layers are arranged in space and time, you must define a composition's spatial attributes, such as its frame size and pixel aspect ratio, as well as its temporal aspects such as its duration and frame rate. Composition settings allow you to specify these characteristics, in addition to the resolution or quality of the display of the Composition window. You may change any of the composition settings at any time.

Frame size

The frame size determines the viewing area of the Composition window. Though you may position images in the workspace outside of this viewing area, only the elements within the visible frame will be rendered for previews and output (Figure 4.5, Figure 4.6 and Figure 4.7).

Figure 4.5. The frame size defines the dimensions of the viewable area of the composition. Over time, an element may move from the "off-screen" work area…

Figure 4.6. … and into the "on-screen" visible frame…

Figure 4.7. … and vice versa. Only elements within the visible frame appear in the final output.

Often, the frame dimensions of the final output determine the frame size of a composition. But if the composition is to be nested in another composition, the frame size may be larger or smaller than the pixel dimensions of the final output. (See "Nested Compositions," later in this chapter, or Chapter 14.)

The Composition Settings dialog box provides a list of preset frame sizes, or you may enter a custom frame size. The frame size you choose is centered in a work space that is limited to the same maximum dimensions as imported image files. As with imported footage files, chances are you'll run out of available RAM before you exceed the maximum image size (up to 30,000 x 30,000 pixels, depending on the output option). For more about the maximum frame size of images, see the sidebar, "Wham, Bam—Thank You RAM,"in Chapter 2.

To set the frame size:

In the Composition Settings dialog box, do one of the following things:

Enter the width and height of the frame size in pixels.


Choose a preset frame size from the pull-down menu (Figure 4.8).

Figure 4.8. Enter the frame dimensions, or choose a preset size from the pull-down menu.

If you are changing the frame size of an existing composition, choose an anchor point from the Anchor section of the Composition Settings dialog box.


You can enter a custom frame size that uses the same image aspect ratio of a preset frame size. First, choose a preset frame size that uses the image aspect ratio that you want to maintain. Check the Lock Aspect Ratio To checkbox and enter a custom frame size. When you enter a value for one dimension, After Effects automatically fills in the other, maintaining the same aspect ratio.

Pixel Aspect Ratio

A typical computer monitor uses square pixels to display an image. Professional video, on the other hand, displays images using non-square pixels. As a result, an image created on a computer can appear distorted when transferred to video, and vice versa.

One of After Effects'great advantages is that it can compensate for the differences in pixel aspect ratios. In fact, when you choose a preset frame size, After Effects automatically selects the corresponding pixel aspect ratio, or PAR. If you want to override this setting, or if you enter a custom frame size, you can choose the correct pixel aspect ratio manually.

The PAR of your composition should match the PAR of the final output. After Effects compensates for any difference between the pixel aspect ratio of the composition and individual footage items. For example, if you add a square pixel footage item into a D1 composition, After Effects automatically resizes the image to prevent image distortion in the final output (Figure 4.9 and Figure 4.10).

Figure 4.9. Incorrectly interpreted as having non-square pixels, this 640 x 480 square pixel image seems to lose its 4:3 aspect ratio in this 720 x 486 (D1/non-square pixels) composition.

Figure 4.10. Correctly interpreted as having square pixels, the image is automatically resized to compensate for a composition set to the D1 standard.

For a detailed explanation of pixel aspect ratio, see the sidebar, "PAR Excellence," in Chapter 2.

To set the pixel aspect ratio of a composition:

In the Pixel Aspect Ratio section of the Composition Settings dialog box, choose a PAR from the pull-down menu (Figure 4.11).

Figure 4.11. In the Pixel Aspect Ratio pull-down menu, choose the pixel aspect ratio that corresponds to your final output.


As suggested above, the most common PARs are "square pixel" and "D1/DV NTSC." Square pixels correspond to formats displayed on computer monitors, or consumer-level video capture cards. D1/DV NTSC corresponds to the non-square pixels used by the professional NTSC video formats (D1, or ITU-R 601) and the DV video standard (mini DV, DVCam, and DVCPro).


Frame size sets the actual pixel dimensions of the composition; resolution determines the fraction of the pixels that are displayed in the Composition window.

By lowering the resolution, you not only reduce the image quality, but also the amount of memory needed to render frames. Rendering speeds increase in proportion to the image quality you sacrifice. In a typical work flow, you work and preview your composition at a lower resolution, and render the final output at full resolution (Figure 4.12 and Figure 4.13).

Figure 4.12. Typically, you work and preview a composition at a lower resolution (in this case quarter resolution)…

Figure 4.13. … then switch to Full resolution when you want to see the image at output quality, or to render the final version.

To set the resolution of the composition:

In the Composition Settings dialog box, choose a setting from the Resolution pull-down menu (Figure 4.14):

Figure 4.14. Choose a resolution from the pull-down menu.

Full—. renders and displays every pixel of the composition, resulting in the highest image quality and the longest rendering time.

Half— renders every other pixel, or 1/4 of the pixels of the full-resolution image in 1/4 of the time.

Third— renders every third pixel, or 1/9 the pixels of the full-resolution image in 1/9 of the time.

Quarter— renders every fourth pixel, or 1/16 the pixels of the full-resolution image in 1/16 of the time.

Custom— renders the fraction of pixels you specify

If you choose Custom from the pull-down menu, enter values to determine the horizontal and vertical resolution of the image (Figure 4.15).

Figure 4.15. If you choose custom from the pull-down menu, enter values to determine the resolution manually. Rendering every fifth horizontal and vertical pixel would equal 1/25th the resolution and rendering time.


You can also change the resolution at any time by using the Resolution pull-down menu of the Composition window (Figure 4.16). See "The Composition Window," later in this chapter.

Figure 4.16. You can also change the resolution using the pull-down menu at the bottom of the Composition window.


You can control the quality setting of individual layers, separate from the composition as a whole. See Chapter 5 for more details.

Frame Rate

The frame rate is the number of frames per second, or fps, used by a composition. Usually, the frame rate you choose matches the frame rate of your output format.

Individual footage items have their own frame rates, which you can interpret. (See "To Interpret the Frame Rate" in Chapter 2). Ideally, the frame rate of the footage and the frame rate of the composition match. If not, After Effects conforms the frame rate of the footage item to that of the composition.

For example, if both the composition frame rate and footage frame rate are 30 fps, then the footage in a layer advances a frame whenever the composition advances a frame. In another scenario, however, the footage might be 10 fps, and the composition, 30 fps. In this case, After Effects distributes one second of footage (10 frames) over one second of the composition (30 frames) by displaying each frame of footage three times. In other words, the composition must advance three frames to display a new frame of the footage layer (Figure 4.17).

Figure 4.17. The frame rate of a footage item is conformed to the frame rate of the composition. In this case, frames of a 10 fps animation are repeated to play in a 30 fps composition to avoid an apparent change in speed.

To set the frame rate of the composition:

In the Frame Rate section of the Composi tion Settings dialog box, enter a frame rate (Figure 4.18).

Figure 4.18. Enter the appropriate frame rate for the composition.

Usually, you choose a frame rate that matches the frame rate of the output format:

NTSC video—29.97 fps

PAL video—25 fps

Film—24 fps

Computer presentation (often via CD-ROM, or Web)—15 fps or 10 fps. Lower frame rates help to reduce file size and conform to data rate limitations.


Film that has been transferred to video uses video frame rates, and has undergone the process of 3:2 pulldown. For more about 3:2 pulldown, see Chapter 2.


Use the Interpret Footage command to set the proper frame rate for a footage item; set the composition's frame rate according to your output requirements. If you are interested in changing the speed of a layer, see Chapter 6.


The duration sets the length of the composition. The duration is expressed using the time display style you set in the Time panel of the Preferences dialog box (as timecode, frames, or feet and frames).

To set the duration of a composition:

In the Duration section of the Composition Settings dialog box, enter the duration of the composition (Figure 4.19).

Figure 4.19. Enter a duration for the composition in the Duration section of the Composition Settings dialog box.

To set the time display preferences:

Choose File > Preferences > Time (Figure 4.20).

Figure 4.20. Choose File > Preferences > Time to choose time display options.

The Time panel of the Preferences dialog box appears (Figure 4.21).

Figure 4.21. Select a display style in the Time panel of the Preferences dialog box.

Choose a display style:

Timecode Base— Make a selection from the pull-down menu, and choose the appropriate counting method from the NTSC pull-down menu (Figure 4.22 and Figure 4.23).

Figure 4.22. If you choose Timecode Base, select a time base and counting method.

Figure 4.23. Choose a counting method, either Drop-Frame timecode, or Non-Drop Frame timecode.

Frames— Enter a starting number in the Start Numbering Frames At field (Figure 4.24).

Figure 4.24. If you choose Frames, enter a starting number.

Feet + Frames— Choose a film format from the pull-down menu (Figure 4.25).

Figure 4.25. If you choose Feet and Frames, select the appropriate film format from the pull-down menu.

Click OK to close the Preferences dialog box.

Counting Time—Non-Drop Frame vs. Drop Frame Timecode

Timecode is a method of counting video frames, developed by the Society of Motion Picture and Television Engineers, or SMPTE. SMPTE timecode is counted in hours, minutes, seconds, and frames. Timecode counts up to just under one day —23:59:59:29.

Because the true frame rate of NTSC video is always 29.97 fps, measuring time accurately in hours, minutes, seconds, and frames can get complicated. To simplify matters, SMPTE timecode rounds off the decimal, and counts at an even 30 fps. However, it can use one of two different counting schemes: Non-Drop Frame or Drop-Frame timecode.

Non-Drop Frame Timecode

Even though the true frame rate of NTSC video is 29.97 fps, Non-Drop Frame (NDF) timecode simply counts 30 fps. Over time, however, the discrepancy results in a small but significant difference between the duration indicated by the timecode display and the actual elapsed time (Figure 4.26). Nevertheless, NDF is easy to understand and calculate, so camera originals and other source tapes usually use NDF timecode. Video equipment typically displays NDF timecode with colons between the hours, minutes, seconds, and frames.

Figure 4.26. For every hour of real time that elapses, non-drop frame timecode counts an additional 3 seconds and 18 frames.

Drop-Frame Timecode

To compensate for the discrepancy caused by the 30-fps counting scheme, SMPTE developed drop-frame (DF) timecode. Drop-frame timecode also counts 30 fps, but it skips two frame numbers—not actual frames—at the end of every minute, except for every tenth minute (Figure 4.27).

Figure 4.27. To accurately reflect actual elapsed time, DF timecode skips two frame numbers at the end of every minute, except for every tenth minute.

If you do the math, you'll find that DF timecode displays durations that very closely match the actual elapsed time. For this reason, master tapes usually use DF timecode. (Of course, the missing numbers also make it very difficult to do timecode calculations manually.) After Effects and other video equipment display drop-frame timecode semicolons between the hours, minutes, seconds, and frames.

To change the settings for an existing composition:

Select a composition in the Project window, or by clicking its tab in the Composition or Time Layout window.

Choose Composition > Composition Settings or press Command-k (Mac) or Ctrl-k (Windows) (Figure 4.28).

Figure 4.28. You can change a composition's settings at any time by choosing Composition > Composition Settings, or by simply pressing Command-k (Mac) or Ctrl-k (Windows).

The Composition Settings dialog box appears.

Enter new settings for the composition (as described in the previous sections).

Click OK to close the Composition Settings dialog box.


You can also access the composition settings from the pop-up menu of the Time Layout window. But using the keyboard shortcut—Command-k (Mac) or Ctrl-k (Windows)—is the quickest way (Figure 4.29).

Figure 4.29. The Time Layout window's menu also gains access to the composition settings. A fine option if you love the mouse, or your keyboard is missing the "k".

Background Color

The default background color of a composition is black, but you can make the background any color you want. Whatever the color, the background becomes the alpha channel if you output the composition as a still image sequence or movie with an alpha channel. Similarly, if you use the composition as a layer in another composition, the background of the nested composition becomes transparent (Figure 4.30). See "Nesting Compositions," later in this chapter.

Figure 4.30. The background of a nested composition becomes transparent.

To choose a background color for the composition:

Choose Composition > Background Color (Figure 4.31).

Figure 4.31. Choose Composition > Background Color.

A background color dialog box appears.

In the Background Color dialog box, do one of the following (Figure 4.32):

Figure 4.32. Click the eyedropper to pick a screen color, or click the swatch to open a color picker.

Click the color swatch to open the color picker.


Click the eyedropper to choose a color from another window.

Click OK to close the Background Color dialog box.


If you need an opaque background—in a nested composition, for example—create a solid layer, as described in "To create a solid color layer," later in this chapter.

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