1080p vs. 1080i

Today, most HDTVs have two picture modes with similar names: 1080p and 1080i. They have the same screen resolution, so what’s the difference between the two modes? Below, we will explore the key differences when comparing 1080p vs. 1080i.
 

Interlaced Scan

Let’s start with the abbreviations — 1080p is short for 1080 “progressive scan”, whereas 1080i is short for “interlaced scan”. In an interlaced scan, odd and even rows of pixels on your screen illuminate in an alternating fashion. Each set of rows is called a “field”. Since the fields flash so quickly (30 times per second!), your eyes do not notice the switch, and your brain perceives a fully assembled picture. The number 1080 refers to the amount of vertical pixels. Each field in an interlaced scan consists of 540 pixels, and adding up each field gives you get a total of 1080 vertical pixels.
 

Progressive Scan

Next, progressive scan takes a different approach to the same 1080 pixels, scanning every row progressively. Your screen refreshes every row a whopping 60 times per second. As you might imagine, this is harder to pull off technologically, but the results are worth it.

Picture Quality

Despite using the same number of vertical pixels, images produced in 1080p are generally much higher quality than those produced with interlaced scan. 1080p is often referred to as “full HD” in order to differentiate it from the lesser quality pictures produced with 1080i or 720p.
 
The difference in quality between 1080i and 1080p is particularly noticeable during scenes that involve a lot of motion, like an epic fight between Batman and Superman, or a high-speed chase through Midtown Manhattan. Interlaced scan will often produce a blurring or tearing effect during these motion-intensive scenes.
 
In addition to movement, image quality is also affected by the size of your screen. Changes in sharpness and clarity when comparing 1080p vs. 1080i will be apparent to most viewers on very large screens. However, unless you have superhuman eyesight, you probably won’t notice much of a difference on smaller screens. For those of us with just average eyesight, we need a TV that’s at least 42 inches in order to notice a significant difference between the formats. Nearly all HDTVs manufactured today are able to “de-interlace” 1080i signals so that they look just as good as 1080p. This makes it even harder for a casual viewer to tell the difference.
 

Cable Confusion

Lastly, cable companies will sometimes deliver a 1080i picture, but then compress the data substantially so that it takes up less bandwidth. This process can smear details or cause pixelated color gradations, especially in scenes with a lot of movement. It’s still technically HD, but it’s not as good as “true” or “full” HD. 


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