Square and non square pixels confuse people. Pixels on screens, the only place where they're really pixels, are square. Video is an exception. Most video formats squeeze as much as they can into the space available, and manage to make life hard for computer integration.

Let's look at PAL video. (All this stuff applies equally to NTSC, in a slightly different way.) If we look at a natural PAL TV screen, it appears to have a 4:3 ratio. That's the natural TV ratio, 4 parts across to 3 parts down. (Films usually go wider, from 16:9 through to 1.85:1 to 2.35:1.) Most computer monitors share this 4:3 ratio: 640x480, 800x600, 1024x768, etc. The fun starts when we look at the actual data that a TV screen uses to make the pictures we see. It's 720x576 — 5:4, not at the 4:3 ratio. If we take video direct from DV with Final Cut Pro, then images will be squished to look tall.

Sometimes it's not noticeable, though often with people or circles on screen, it is. To fix it, simply resize the image in Photoshop to 768x576. Image > Image Size with Resample Image on and Constrain Proportions off. Stick it in an action and forget about it.

Why square and non-square? 768x576 or 800x600 use regular square pixels, at 4:3. 720x576 displays at 4:3 by using non-square pixels, slightly wider horizontally than vertically. If you watch Final Cut Pro capturing DV footage, it's thin; it doesn't have time to desquish it for you. When you watch it back later, a display option "View as Square Pixels" helps you stay sane.

Why do you need to know? Final Cut (1.2.5) is a little NTSC-friendly. PAL support doesn't quite extend to importing square PAL sizes properly, so you have to manually do the conversion to 720x576. Make sure this happens in any still graphics that go into Final Cut.

NTSC? It's got a similar issue, though their 30fps vs our 25fps means there's less room for data, and they squish it the other way, to 720x480. Their square res is 720x540, meaning that images need to be expanded vertically rather than horizontally to look right.

Because of this, Final Cut (1.2.5 again) does a weird thing to simulate square PAL pixels — it squishes vertically in rather than horizontally out. Fine, except it can sometimes make interlaced video look very strange indeed. Sometimes Final Cut needs to be used without the "View as Square Pixels" display option.