Apple MA261Z/A User Manual - Page 764

Understanding Digital SD Video Non-Square Pixels When creating graphics for standard definition video, you need to consider the fact that the digital video pixels are considered to be non-square (taller than wide-NTSC, or wider than tall-PAL) compared to your computer graphics program that uses square pixels. Non-square pixels are also referred to as rectangular pixels. Note: Some computer graphics programs support non-square pixels, making it simpler to create graphics for standard definition video formats like NTSC and PAL. For high definition video formats, you can simply create square pixel graphics, which means designing graphics with exactly the same image dimensions as your HD format. Reconciling the difference between non-square pixels and square pixels can cause a lot of confusion for beginning video graphic designers, but the best rules of thumb are to: Â Use a graphics application that supports non-square pixels, such as Adobe Photoshop. In this case, you create your graphics with the proper dimensions and pixel aspect ratio throughout the entire post-production process. Â Keep your destination video frame size in mind and follow the table on page 765 when designing graphics in your graphics application. Note: There is no accepted standard for the exact aspect ratio of non-square standard definition video pixels. Different manufacturers may assume different pixel aspect ratios when designing their software. Fortunately, these differences tend to be very small, so in many cases you may not notice a difference between a pixel aspect ratio of, say, 0.9 and 0.89. Since every non-square video frame size has an equivalent square frame size that will look correct in SD video, it's easy to create your graphics with a usable frame size. The steps below tell you how. See "Pixel Aspect Ratios in SD Video Signals Versus Computer Displays" on page 766 for more background information on this topic. Graphics for projects that will be output to high definition video, or for video that will be played only on computers and doesn't use any captured SD video footage, simply need a frame size that matches the sequence frame size. No alterations are needed. 764 Part IX Effects