indessed roscivs

Today’s installment is about a more straightforward subject: resolution.

Resolution

“Resolution” refers to how many pixels an image has. For example, take a look at this fish, courtesy Wikipedia:

The fish on the left is made up of 1,840 little squares (”pixels”). The fish on the right has only 460 squares. As a result, the fish on the left looks better—the curves look less “jaggy”, and you can see more detail (such as the slight “mouth” shape that isn’t present on the fish on the right).

Note that the resolution (or number of squares) doesn’t directly affect the size of the image. The fish on the right has the same resolution (460 squares, 23 wide and 20 tall) no matter how big each pixel is. If each square is one inch, then you’ll have a large picture—23 inches wide and 20 inches tall. Alternatively, if each square is 1/100th of an inch (most computer monitors have pixels around this size), then the fish will be about a fifth of an inch tall—very tiny. But in both cases, the resolution is exactly the same.

The difference is that, with a 20-inch fish, you can very easily see the blocks that make up the picture—they’re one inch square, after all! With a fifth-inch fish, you won’t be able to see the individual pixels unless you look very closely. If you were sitting a few feet away, you probably wouldn’t see much of a difference between a 1,840-square fifth-inch fish and a 450-square fifth-inch fish. But you’d still see a big difference between the two resolutions with a 20-inch fish, even at a few feet away.

So how does this translate into video terms? Digital video is made up of pixels, just like the fishies—although video uses a lot more pixels. “Regular” television is approximately 640×480 pixels (about 300,000 “little squares”). I say “approximately” because normal television typically is not digital, so it looks a lot worse. For things like analog cable or VHS tapes, it’s more equivalent to half that—320×240 pixels. 640×480 is closer to the resolution of digital cable and DVDs.

Remember yesterday’s discussion about aspect ratio? Notice that 640×480 is 1.33:1, the “square” format of older TVs. But movies are typically “widescreen”, typically with an aspect ratio of 2.35:1 or 1.85:1. So cable and broadcast television are moving increasingly towards the 16:9 ratio, and producing video in one of three popular resolutions: 852×480, 1,280×720, and 1,920×1,080—each exactly 16:9. These three resolutions are given other names, such as 480p or “enhanced definition” (EDTV) for the first, 720p or “high definition” (HDTV) for the second, and 1080p for the third (also commonly just referred to as “HDTV”). The name is in essence just the number of pixels tall, with a “p” added on (referring to “progressive scan,” which we’ll talk more about when we get to interlacing).

But itself, the resolution of the video is relatively uninteresting. The more important part is the resolution of the television or projector you’re considering. If you get a widescreen TV, it will be either 852×480, 1280×720, or 1920×1,080. How important the resolution is depends on (a) the resolution of the incoming video, and (b) the size of your screen. The resolution of the incoming video is important because if all you’ll ever watch on it is DVDs and analog cable, there’s no point in getting something with more than 480p (EDTV) resolution. The size of your screen is important because if you’re getting a 27″-diagonal screen, you probably won’t be able to see much of a difference between 720p and 1080p (just like you won’t see much of a difference between the two fifth-inch fishies). If your screen is more like 100″ diagonal, you’ll likely be able to see more of a difference.

To sum up, more pixels = better, but depending on your video inputs (e.g. DVDs and analog cable vs. HD-DVDs and digital HD cable) it might not make a difference. Your screen size matters too–watching a 320×240 picture on my 4″ Palm Pilot screen is an enjoyable experience. Watching the same picture on my 120″+ projector screen is not.

Next week, we’ll continue the series with an article about frame rates.

This entry was posted on Thursday, May 17th, 2007 at 8:19 pm and is filed under movies. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.