then export your project to the industry-standard Advanced Authoring Format (AAF) for
transfer to an editing system with more powerful hardware. You can then perform the final
online edit with full-resolution clips on that system.
About aspect ratios
Aspect ratio
specifies the ratio of width to height. Video frames have an aspect ratio (frame
aspect ratio), and so do the pixels that make up the frame (pixel aspect ratio). Some video
cameras can record various frame aspect ratios, and different video standards use various
pixel aspect ratios.
Using Help | Contents | Index Back 99
Adobe Premiere Pro Help Capturing and Importing Source Clips
Using Help | Contents | Index Back 99
When imported clips are created using a different pixel or frame aspect ratio than your
project, distortions can result. Adobe Premiere Pro automatically attempts to detect and
compensate for the pixel aspect ratio of source clips. If a clip appears distorted in Adobe
Premiere Pro, you can use Adobe Premiere Pro to manually indicate its pixel aspect ratio.
It's important to reconcile pixel aspect ratios before reconciling frame aspect ratios,
because an incorrect frame aspect ratio is often caused by misinterpreting a source clip's
pixel aspect ratio.
About frame aspect ratio
Frame aspect ratio
describes the ratio of width to height in the dimensions of an image.
For
example, DV NTSC has a frame aspect ratio of 4:3 (or 4.0 width by 3.0 height). For
comparison, a typical widescreen frame has a frame aspect ratio of 16:9; many cameras
that have a widescreen mode can record using this aspect ratio. Many films have been
shot using even wider aspect ratios.
A 4:3 frame aspect ratio (left), and a wider 16:9 frame aspect ratio (right)
When you import clips shot in one frame aspect ratio into a project that uses another
frame aspect ratio, you must decide how to reconcile the different values. For example,
there are two common techniques for showing a widescreen movie with a 16:9 frame
aspect ratio on a standard television with a 4:3 frame aspect ratio. You can fit the entire
width of the 16:9 frame in a black 4:3 frame (called
letterboxing
), which results in black
bands above and below the widescreen frame. Or you can fill the 4:3 frame vertically with
the entire height of the 16:9 frame, varying the horizontal position of the 16:9 frame
behind the narrower 4:3 frame so that important action is visible in the 4:3 frame (called
pan & scan
). In Adobe Premiere Pro, you can implement either technique by using Motion
effect properties such as Position and Scale (see “Using the Motion effect” on page 240).
About pixel aspect ratio
Pixel aspect ratio
describes the ratio of width to height in a single pixel of a frame. Pixel
aspect ratios vary because different video systems make various assumptions about the
number of pixels required to fill a frame. For example, many computer video standards
define a 4:3 aspect ratio frame as 640 pixels wide by 480 pixels tall, which results in
square
pixels. At the same time, video standards such as DV NTSC define a 4:3 aspect ratio
frame
as 720 x 480 pixels, which results in narrower, rectangular pixels because there are more
pixels within the same frame width. The computer video pixels in this example have a pixel
aspect ratio of 1:1 (square) while the DV NTSC pixels have a pixel aspect ratio of 0.9
(nonsquare). DV pixels, which are always rectangular, are vertically oriented in systems
producing NTSC video and horizontally oriented in systems producing PAL video. Adobe
Premiere Pro displays a clip’s pixel aspect ratio next to the clip’s image thumbnail in the
