Adobe Photoshop CS3 - Manual (Page 558)

PHOTOSHOP CS3
User Guide
551
4:3 frame aspect ratio (left), and wider 16:9 frame aspect ratio (right)
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. 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.
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.
Note: When copying or importing images into a nonsquare pixel document, Photoshop automatically converts and
scales the image to the pixel aspect ratio of the document. Images imported from Adobe Illustrator CS3 are also properly
scaled.
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
Create an image for use in video
1 Create a new document.
2 From the Preset menu in the New dialog box, choose the Film & Video preset.
3 Choose the size that’s appropriate for the video system on which the image will be shown.
4 Click Advanced to specify a color profile and specific pixel aspect ratio.
3
4 16
9
B
A
C