1080i VS 1080p The Difference

1080i vs. 1080p: What's the Difference?

Progressive (1080p) video is considered better than interlaced (1080i), but it's not always clear why; here's what's actually happening on your TV screen.

Today's HDTVs can display beautiful, 1,920 X 1,080-pixel video, but the actual quality of what you're viewing depends on the source material. A lot of the time, you're not seeing exactly 1080p. In fact, most TVs today have two modes with similar names: 1080i and 1080p. Both have the same screen resolution, so what's the difference between the two? Here are five things you need to know:

1080i video is "interlaced." 1080i video plays back at 60 frames per second, but that's a bit deceptive, because it's actually broadcast at 30 frames per second. The TV then displays those frames twice, the first pass is 1,920 X 540 for the even scan line field, and the second pass is 1,920 X 540 for the odd scan line field. The process by which this occurs is called interlacing. It contributes to a sense of motion and reduces perceived flicker.

1080p video is called "progressive scan." In this format, 1,920-by-1,080-pixel high-definition movies are progressively drawn line after line, so they're not interlaced. On paper, that may not seem like a huge deal. But in the real world, what you end up seeing looks sharper and more defined than 1080i, particularly during scenes with a lot of fast motion.

Sometimes 1080p is termed "Full HD" or "True HD," to distinguish it from 1080i or 720p video. Blu-ray discs contain 1080p video at 24 Frames Per Second, and then, using a method known as 3:2 pulldown, display it at 30 frames per second on screen.

Data compression can confuse the issue. Sometimes cable companies will deliver a 1080i picture, but then compress the data significantly in order to use up less bandwidth. The result can mean smeared details or pixelated color gradations in certain scenes. It's still technically HD, and still looks better than standard-definition cable, but it's not as good as it could be.

This also happens with 1080p streaming Internet video, but in that case, it's usually dependent on the speed of your data connection. In fact, Blu-ray is currently the only practical format for watching lots of pure 1080p content. Even the latest Apple TV, which supports 1080p streaming, does so in a compressed format that loses a bit of quality (although it still looks quite good).

Both formats look similar on smaller TVs. As a general rule, you need a larger TV to notice the difference between 1080i and 1080p. Depending on your eyesight, you can probably pick up the difference on a 32-inch LCD if you're particular about it. But most consumers don't really see a marked difference until at least a 42-inch screen, if not larger. In fact, many people are perfectly happy with 720p HDTV sets even at higher sizes; we recently named one, the 51" Samsung PN51E490B4F, best Choice for budget large-screen HDTVs.

1080p isn't even the best anymore. Technology never stands still, of course. Five years from now, you'll probably just want Ultra High Definition (aka 4K) video instead. (For a closer look at 4K video, check out What is Ultra HD?) But for now, if you're a videophile who appreciates a sharper picture, 1080p is definitely the way to go—both in HDTV capability and in the source material you're viewing.

720p and 1080p explained

720p explained

720p is the shorthand name for a category of HDTV video modes. The number 720 stands for the 720 horizontal scan lines of display resolution (also known as 720 pixels of vertical resolution), while the letter p stands for progressive scan or non-interlaced.

Progressive scanning reduces the need to prevent flicker by filtering out fine details, so sharpness is much closer to 1080i than the number of scan lines would suggest. A 720p frame has about 1 million pixels. Compared to it, a 1080p frame has 2 million pixels so the amount of detail doubles. However in practice the difference between 1080p vs 720p is not as obvious as the one between standard definition vs high definition (480p vs 720p). For example a regular DVD isn’t even considered high definition because it is either 720×480 (NTSC) or 720×576 (PAL) but it looks much better than regular NTSC or PAL TV broadcasts and not as great as 720p. That being said, you do get more detail from 1080p than from any resolution if you have the “winning” formula for screen size, resolution and viewing distance – that is if you have the optimum conditions to get the most out of 1080p.

1080p explained:
The number 1080 represents 1,080 lines of vertical resolutions (1,080 horizontal scan lines), while the letter p stands for progressive scan (meaning the image is not interlaced). 1080p can be referred to as full HD or full high definition although 1080i is also “Full HD” (1920×1080 pixels). The term usually assumes a widescreen aspect ratio of 16:9, implying a horizontal resolution of 1920 pixels. This creates a frame resolution of 1920×1080, or 2,073,600 pixels in total.

The only pure 1080p content comes from high definition DVDs like Blue Ray and HD DVD. Regular DVDs are way below that, having just 480p or 576p. You also get HD content from TV broadcasts but for now only 1080i and 720p. Basically 1080i offers pretty much the same amount of detail as 1080p but the quality of fast moving scenes is a bit inferior to 1080p. To understand this better read the 1080p vs 1080i guide. 720p content will of course look the same (or very similar) on a 1080p screen as it does on a 720p screen because what also matters is the content resolution not just the screen resolution.

Here is a sample with the difference between 720p and 1080p:

480i - Total image resolution 337,920 pixels

480p - Total image resolution 337,920 pixels

720p - Total image resolution 921,600 pixels (roughly equivalent to a 1 mega pixel camera)

1080i - Total image resolution 2,073,600 pixels (equivalent to a 2 mega pixel camera)

1080p - Total image resolution 2,073,600 pixels (equivalent to a 2 mega pixel camera)

More lines is nice but don't forget about the 'p' and 'i' in the 720p, 1080i and 1080p. The letter is an abbreviation for the type of scan the TV uses -- 'p' stands for progressive and 'i' stands for interlaced.