Width-to-height ratio of individual pixels—differs from image format. DV and HD have different PAR; critical for scaling in post and VFX work.
You're working with DV footage and notice when transferring it to your NLE that your shots suddenly look distorted—too wide or too narrow. This isn't a mistake with your camera, but a classic problem with the Pixel Aspect Ratio. While the image format (16:9, 4:3) describes the relationship of the overall image dimensions, the Pixel Aspect Ratio (PAR) determines whether each individual pixel is more square or rectangular. With standard DV, a pixel is not square—this is the crucial difference compared to modern HD or 4K cameras, where pixels are usually 1:1 (square).
In practice, this happens like this: You shoot with an older DV cam in 4:3 format. The technical resolution is 720×480 (NTSC) or 720×576 (PAL), but the PAR is 0.9 or 1.2—not 1.0. This means that if the pixel dimensions are interpreted directly, your image will be displayed distorted. Your NLE (Premiere, Final Cut, DaVinci) needs to know this PAR upon import and automatically correct it. If you enter the wrong PAR values or import footage without PAR metadata, the monitor will show you distorted faces and skewed lines, even though the original footage is clean. This isn't a focusing error—it's a metadata issue.
In modern workflows, this is less critical because HD and 4K material works with square pixels by default (PAR 1:1). Nevertheless, you need to be aware of it: when digitizing archives, restoring archival material, or working with broadcast standards (formerly PAL/NTSC), PAR values play a role. Errors happen quickly during scaling and rendering—you upscale your image to 1080p, but if the PAR is misinterpreted, it will be distorted again. In editing, you ensure that your project settings reflect the correct PAR for your source material. For modern production material, you don't need to worry much, but when migrating older formats or dealing with international material (PAL vs. NTSC), it's a real problem that you need to address immediately during digitization.