Pixel Aspect Ratio; Using Assets With Various Aspect Ratios - Adobe PREMIERE PRO 2 Manual

ADOBE PREMIERE PRO 2.0 31
User Guide

Pixel aspect ratio

Pixel aspect ratio describes the ratio of width to height of a single pixel in 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 high, which results
in square pixels. 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), whereas 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 Project panel.
If you display rectangular pixels on a square-pixel monitor without alteration, images appear distorted; for example,
circles distort into ovals. However, when displayed on a broadcast monitor, the images appear correctly proportioned
because broadcast monitors use rectangular pixels. Adobe Premiere Pro can display and output clips of various pixel
aspect ratios without distortion because it attempts to automatically reconcile them with the pixel aspect ratio of your
project. You may occasionally encounter a distorted clip if Adobe Premiere Pro interprets pixel aspect ratio incor-
rectly. You can correct the distortion by manually specifying the source clip's pixel aspect ratio.
A B C
Pixel and frame aspect ratios
A. 4:3 square-pixel image displayed on 4:3 square-pixel (computer) monitor B. 4:3 square-pixel image interpreted correctly for display on 4:3
non-square pixel (TV) monitor C. 4:3 square-pixel image interpreted incorrectly for display on 4:3 non-square pixel (TV) monitor

Using assets with various aspect ratios

Adobe Premiere Pro automatically attempts to preserve the image aspect ratio of imported assets, sometimes
changing the pixel aspect ratio, the frame dimensions, or both so that the asset does not appear cropped or distorted
when used in a sequence. Assets created in an Adobe Creative Suite application contain metadata that allows Adobe
Premiere Pro to make the calculations automatically and precisely. For assets lacking this metadata, Adobe Premiere
Pro applies a set of rules to interpret pixel aspect ratio.
When you capture or import NTSC footage with the ATSC frame size of 704 x 480, the D1 frame size of 720 x 486,
or the DV frame size of 720 x 480, Adobe Premiere Pro automatically sets the pixel aspect ratio for that asset to
D1/DV NTSC (0.9). When you capture or import footage with the HD frame size of 1440 x 1080, Adobe Premiere
Pro automatically sets the pixel aspect ratio for that file to HD 1080 Anamorphic (1.33). When you capture or import
PAL footage with the D1 or DV resolution of 720 x 576, Adobe Premiere Pro automatically sets the pixel aspect ratio
for that file to D1/DV PAL (1.067).
For other frame sizes, Adobe Premiere Pro assumes that the asset was designed with square pixels and changes the
pixel aspect ratio and frame dimensions in a way that preserves the asset's image aspect ratio. If the imported asset
is distorted, you may need to change the pixel aspect ratio manually.
When you drag an asset into a sequence, Adobe Premiere Pro centers the asset in the program frame by default.
Depending on its frame size, the resulting image may be too small or overcropped for the needs of the project. If so,
you may need to change its scale. You can do this manually or have Adobe Premiere Pro do it automatically whenever
you drag an asset into a sequence.