Using Square or Nonsquare Pixels When Creating Graphics
When you’re preparing to import graphics into Motion, be aware of the pixel aspect ratio you’re using and whether your project requires you to work with square or nonsquare pixels.
Use nonsquare pixels for standard-definition projects in NTSC or PAL.
Use square pixels for full-raster high-definition projects as well as multimedia video that will be played back only on computers and doesn’t use captured video footage.
Use square pixels for graphics used in projects with decimated raster frame sizes, such as DVCPRO HD formats recorded with a squeezed 1280 x 1080 frame size, but which are later stretched during playback to 1920 x 1080. Raster decimation is a strategy for lowering the data rate of recorded HD video; however, the final result is almost always mastered at the nearest corresponding full-raster resolution. By creating composited graphics and animation at the full-raster resolution used for output, you’ll simplify your asset creation, and guarantee the highest quality.
Graphics created on a computer, whether scanned, painted, or rendered, will look distorted on a standard-definition video display unless you account for the different pixel aspect ratio. Fortunately, this is easy to do, because every nonsquare video frame size has an equivalent square frame size that you can use to create your graphics.
In your graphics application, create a frame size that’s the square pixel equivalent of the video frame size you’re using.
See the chart below for equivalent sizes. For example, if you’re working in DV-PAL with a nonsquare video frame size of 720 x 576, your graphic should have a square pixel frame size of 768 x 576.
Create the graphic.
Do one of the following:
In your graphics program, rescale the graphic from the square frame size used to create it to the nonsquare equivalent used in Motion.
Save your image as is.
In your Motion project, select the object in the Media list of the Project pane, open the Media Inspector, then choose the correct aspect ratio from the Pixel Aspect Ratio pop-up menu.
Video format | Nonsquare 4:3 pixel size (Motion) | Aspect ratio | Square pixel size (graphics program) |
|---|---|---|---|
601-NTSC 4:3 | 720 x 486 | 0.9 | 720 x 547 |
601-NTSC 16:9 Anamorphic | 720 x 486 | 1.2 | 853 x 486 |
DV-NTSC 4:3 | 720 x 480 | 0.9 | 720 x 540 |
DV-NTSC 16:9 Anamorphic | 720 x 480 | 1.2 | 853 x 480 |
601/DV-PAL 4:3 | 720 x 576 | 1.07 | 768 x 576 |
601/DV-PAL 16:9 Anamorphic | 720 x 576 | 1.42 | 1024 x 576 |
720i/p high definition | NA | 1.0 | 1280 x 720 |
1080i/p high definition | NA | 1.0 | 1920 x 1080 |
Working with Standard-Definition (SD) Video Displays
Standard-definition (SD) video displays differ from computer displays in a significant way (aside from interlacing): computer displays represent images using a grid of square pixels, while SD video displays use rectangular pixels.
SD NTSC pixels are narrower than computer pixels and SD PAL pixels are wider than computer pixels. As a result, a 720 x 486 pixel image looks different on a computer display than it does on a video monitor. For example, if you capture a clip of video with a globe in the picture, export a frame, and look at this frame in a graphics application, you’ll see something like this:
To display nonsquare pixel video correctly in Motion, choose Correct For Aspect Ratio in the View pop-up menu above the Canvas.
Note: Because full-raster high-definition video uses only square pixels, its images always appear correctly when displayed on SD video displays.