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What’s the Difference Between 720p, 1080i and 1080p Screen Resolutions for HDTVs?

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What’s the Difference Between 720p, 1080i and 1080p Screen Resolutions for HDTVs?
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What’s the Difference Between 720p, 1080i and 1080p Screen Resolutions for HDTVs?

Since their introduction in 1998, high-definition televisions, or HDTVs, have supplanted standard-definition televisions, thanks to the higher quality images they produce. HDTV uses a digital television signal as opposed to an analog signal, but not all digital television (DTV) is also HDTV. Ideal for cinephiles, gamers, and sports enthusiasts, HDTV allows viewers to enjoy a cinema-like experience at home with the widescreen viewing angle. High-definition televisions can be purchased at electronics retailers, some department stores, as well as through Internet marketplaces such as eBay. Shoppers have several options when it comes to choosing an HDTV, including 720p, 1080i, and 1080p, which each refer to the screen resolution. This article will explore the differences between the three as well as address the terms consumers should know when looking to buy HDTVs.

The Difference Between 720p, 1080i, and 1080p

Televisions measure resolution in lines of pixels. A pixel is a dot on a screen, which combines with others to create the colors and images displayed. "High definition" simply refers to the fact that an HDTV has a greater resolution, and a greater number of lines, than a standard - definition television (SDTV), or even an enhanced - definition television (EDTV). The chart below explains the differences between the terms.

Term

Resolution

Lines

Pixel Dimensions

SDTV

480i

480

640x480 pixels

EDTV

480p

480

852x480 pixels

HDTV

720 p

720

1280x720 pixels

HDTV

1080 i

1080

1920x1080 pixels or 1440x1080 pixels

HDTV

1080 p

1080

1920x1080 pixels

As seen above, high-definition television uses at least 720 lines, or as many as 1080 lines, whereas standard-definition TVs or enhanced-definition TVs have just 480 lines. As a result, HDTVs have a resolution much higher than that of standard-definition TVs (as much as 10 times greater), and the higher resolution means greater detail can be shown.

Scan Technology

Also of note is the letter appended to the resolution, either a "p" or an "i." These stand for "progressive" and "interlaced," respectively, and refer to the way the image is processed, or scanned. Interlacing means that the pixel lines are scanned using alternating rows, so the odd-numbered lines appear before the even-numbered lined. This happens faster than the human eye can detect, but it does create a flickery image. Progressive scan, on the other hand, means that the pixels and lines are scanned sequentially, rather than in an alternating pattern. As a result, progressive scanning creates a more stable image. This is part of the reason that EDTV, while it has the same number of lines as an SDTV, is considered "enhanced." Most consumers will want to opt for progressive-scan technology rather than interlacing technology because of the better image quality.

Terms to Know When Buying HDTVs

There are several factors that contribute to image quality in an HDTV beyond the resolution and scanning technology used. Knowing a few key terms can make the process of shopping for an HDTV, and narrowing down the choice of whether to buy a 720p, 1080i, or 1080p HDTV, a simpler process.

Aspect Ratio

As mentioned before, HDTVs use a widescreen format, which is a type of aspect ratio. An aspect ratio indicates the proportional relationship between the length and height of an image. SDTV uses a 4:3 aspect ratio for a relatively square image. A widescreen aspect ratio of 16:9 creates a rectangular image that is easier for human eyes to process because it essentially allows a sweeping left-to-right movement as opposed to an up-and-down direction. This also captures more of the image on screen, which is ideal for films and sporting events.

Contrast Ratio

Another key factor that contributes to the quality of an HDTV is the contrast ratio, which is the measure of the amount of light between the whites and blacks produced by the television. While this has nothing to do directly with screen resolution, is does help determine the colors displayed. A contrast ratio of 1,000:1 means the white is 1,000 times brighter than the black. Generally, a higher contrast ratio means that darker images will have more depth or detail. However, standards vary between manufacturers, and there are actually two types of contrast ratios typically given, the static ratio and the dynamic ratio. The static ratio is generally considered to be more accurate.

Frame Rate and Refresh Rate

Frame rate is essentially a frequency, indicating how many frames are displayed per second. In film and video, this is measured in frames per second, or fps. Frame rate in HDTVs is indicated by the number of frames, as well as the type of scan (either progressive or interlaced). Film is shot at 24 fps, while video is recorded at 30 fps. HDTVs offer users a variety of frame rate options, as outlined below.

Frame Rate

Explanation

Compatible with...

24p

Mimics the natural recording speed for film; if the TV doesn’t support 24p, it is converted to 30p via a process called 2:3 pulldown

1080p

30p

Mimics the natural recording speed for film

1080p

60p

The standard for progressive-scan HDTVs; it takes 30p and simply repeats each frame twice within 1 second

1080p, 720p

60i

The standard for interlace-scan HDTV

1080i

HDTVs that support 24p better recreate the source material with minimal translation needed, which makes them ideal for cinephiles. However, in order to offer the best performance in the 1080p/24 format, an HDTV should have a refresh rate that is a multiple of 24.

Refresh Rate

Refresh rate measures how many times the television updates the picture, as opposed to the number of frames displayed. Because it is essentially a frequency, it is measured in Hertz (Hz). Most HDTVs support a standard 60 Hz refresh rate that works with the 60p or 60i frame rate, updating the picture the same number of times as the number of frames displayed. However, newer HDTVs may offer a refresh rate that is a multiple of 24, such as 120 Hz or 240 Hz, which means the picture is updated twice for every frame, or four times for every frame, respectively. While this can help reduce judder (which is the motion jerkiness that results from the discrepancy between frame rate and refresh rate), it can also lead to an almost unnatural-seeming motion.

Factors to Consider When Buying an HDTV

While the differences between HD resolutions may seem large, the reality is with smaller screen sizes, the difference is negligible. For this reason, most HDTVs with 32-inch or smaller screens use 720p. The progressive-scan technology used by 1080p and 720p HDTVs allows for a sharper image than a 1080i HDTV. While many major broadcast networks use the interlacing technology for a 1080i resolution, 1080 p and 720 p HDTVs can both accept 1080i signals. A 720p HDTV will scale the image down slightly, but as stated, with a small screen the difference will hardly be noticed. With a 1080p signal, no scaling occurs; the signal is simply translated from an interlaced one to a progressive one.

Connecting External Devices

Consumers can enjoy high-definition movies with Blu - ray players, which support 1080p/24 natively. However, Blu-ray players are also equipped with the ability to scale to 1080p/60, 1080i/60, and 720p if the television does not support 1080p/24, so having a Blu-ray player should not influence a shopper’s decision.

Some games consoles, including the Microsoft Xbox 360 and Sony PlayStation 3, also support HD in either 720p or 1080p, allowing users to play games, play movies, and stream online content. However, most games themselves are created in 720p and are converted to 1080p by the games system. Gaming enthusiasts should note that they are in most cases not losing any detail by choosing a 720p HDTV. Some HDTVs may offer a special gaming mode that optimizes settings for gaming to minimize lag time.

Buying 720p, 1080i, or 1080p HDTVs on eBay

When you’re ready to buy an HDTV, start by visiting eBay’s Electronics department. From there, you can navigate to TV , Audio , & Surveillance, followed by Televisions. eBay will let you narrow your results further by the screen size and the maximum resolution, along with other features, such as display technology and brand. Further options include free shipping and expedited shipping. In addition, you can search for an item directly from eBay’s home page by entering a keyword, such as "32- inch 720 p HDTV" in the search box.

Buying with Confidence on eBay

When you’re looking at products on eBay, be sure to check the seller’s rating and feedback history. These are left by shoppers who have bought from the seller before, so a good rating and positive feedback indicate a trustworthy seller. You can also filter search results using eBay’s Advanced Search feature, selecting the option to display items from only Top - rated Sellers. After you’ve bought your items, you may want to ask the seller to insure your purchase when it ships, which protects it against loss or theft.

Conclusion

Ultimately, the differences between 720p, 1080i, and 1080p screen resolutions come down to two factors: the number of lines in the resolution and the type of scanning technology. A 720p HDTV has 720 lines of pixels, as opposed to the 1080 found in 1080i and 1080p resolutions. However, both 720p and 1080p offer an advantage over 1080i in that they use progressive scanning, which creates a clearer image because the pixel lines in an image are scanned and assembled sequentially, as opposed to interlacing, which scans and assembles odd-number pixel lines before even-numbered lines.

If consumers opt for a 1080p full HDTV, they will also want to look into the supported frame rates and refresh rates, as these can vary. Some 1080p HDTVs will offer a 24p frame rate, which is ideal for watching movies because film records at a speed of 24 frames per second. Gamers will want to remember that while consoles such as the Xbox 360 or PlayStation 3 support 1080p, most games with high-definition support have a native 720p resolution, so a 1080p HDTV does not offer any inherent advantage while gaming. For consumers seeking an HDTV, no matter what the resolution, eBay is an excellent place to start.

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