In this guide I am going to explain to you what the resolution is, the various resolutions found in TVs and HDTVs, as well as the difference between them. I will also describe in detail why buying a HDTV with the highest resolution (1080p) might not give you an advantage over one that has a lower resolution (720p). When you finish reading this guide, you will have enough knowledge about this matter to avoid some serious mistakes that sales people and marketers want you to make. So let’s get started, shall we?
What Is Resolution?
It is a measure that has two components – width (horizontal resolution) and height (vertical resolution). The resolution is used to describe how accurate a device is in replicating an image and how much detail it can offer to the viewer. It is a measure used not just for TVs or displays but also for printers and any other devices that are used to produce an image. Even our eyes acuity can be expressed as resolution (and it is huge compared to the one of any device). When it comes to TVs and displays, resolution is expressed as the number of pixels that the screen has on vertical and horizontal axis. If you multiply the two numbers you get the total number of pixels that the TV has (expressed in megapixels or millions of pixels). This is more commonly used to describe the digital cameras resolution than TVs or displays. As I said above, the resolution measures the number of pixels. But what are the pixels? Pixels are appear as little dots that together form the picture you see. Each pixel can have one specific color depending on the part of the image it must represent. All flat screen TVs (plasma, LCD, etc.) have a fixed number of pixels. For example a 1080p plasma TV has a resolution of 1920×1080 pixels – 1920*1080=2,073,600 witch roughly is 2Mp (2 megapixels or 2 millions of pixels).
Resolution is also a measure used to define a video signal. You can have for example a plasma TV with a resolution of 1920×1080 pixels (1080p) but the video signal of the TV channel you are watching can be (and it is in many cases) smaller – 1280×720 (720p). In this case the TV performs a process called “upconversion” to scale the TV signal to it’s native resolution. If the TV receives a signal with a higher resolution than it’s native resolution then it performs an opposite process called “downconversion”. Both upconversion and downconversion are basically resizing processes.
As I said above the resolution has two components – vertical and horizontal – but in most of the cases you will see the resolution expressed as a single number followed by a letter (e.g. 1080p, 1080i, 720p, etc). The number is the vertical resolution and the letter stands for progressive scan (p) or interlaced scan (i) – more about that later. The reason why we find resolution expressed as a single number (vertical resolution) is that the horizontal resolution varies. It is not uncommon to find two HDTV sets with the same vertical resolution but with different horizontal resolutions.
Progressive vs. Interlaced
1080p and 1080i – same number different letter. The “p” stands for progressive while “i” stands for interlaced. These are two methods to form an image on the screen. Progressive means that the image is generated completely in one pass, line by line, one after the other in 1/60 of a second. In the case of 1080p it means that there are 1080 lines drawn on the screen consecutively (1,2,3,4,etc.). Interlaced means that the complete image is generated completely after two passes. In each pass only every other line is drawn on the screen – usually it starts with odd lines – and each pass takes 1/60 of a second so to generate a complete frame it takes 1/30 of a second. For 1080i example first are drawn lines 2,4,6,etc. and in the second pass are drawn lines 1,3,5,etc. But since one image is more than a thousand words let’s see how it actually looks.
|Interlaced image generation:
In the first pass odd lines are drawn and in the second pass the other lines are drawn.At the end of the two passes the viewer has the perception of one complete image.
|Progressive image generation
The image is drawn line after line in one single pass
The difference between the two methods is that with progressive you get more frames per second (FPS). Progressive generates 60 FPS while interlaced generates only 30 FPS (60/2). In real life this difference is noticeable if you watch high speed scenes like sports or action movies. With this type of content progressive scan will offer you an advantage and the image will remain sharp during fast scenes. If you watch high speed scenes in interlaced content you may notice softer edges and a slight loss of detail especially around the edges. It is not a huge difference but it is noticeable if you pay attention to it. As I said the difference is noticeable only in fast action scenes and if you are to watch a National Geographic documentary about exotic flora you won’t see any difference since that has no fast moving content. You should also keep in mind that progressive and interlaced have more meaning when referring to content sources than the capabilities of a TV or HDTV because pretty much all TVs support progressive scan content, but many content sources happen to be interlaced. Most of the HD broadcasts are either 720p or 1080i and at this point there are no 1080p broadcasts. So if you intend to watch sports, action movies, or anything else that has fast-moving scenes, the best is to use a signal that generates the on-screen picture using the progressive method. The combination of a plasma TV and a progressive signal is the best for this type of content as opposed to an interlaced signal on an LCD TV which offers a lower quality for the fast-action scenes (LCD TVs have lower refresh rates than plasma TVs).
Difference Between Resolutions
Most common resolutions in today’s HDTVs are 720p and 1080p. There are however 16 more resolutions defined by the Advanced Television Systems Committee (ATSC). Those other 16 resolutions are supported for digital broadcasts but are not very common. The difference between the various resolutions is the amount of detail available to the viewer in a specific area of the screen (or the whole screen). Basically a higher resolution means there are many more pixels available for the same area and because of that the detail is higher. Below you have an example of three common resolutions compared. Note that the size of the pixels and the ratio between them are not necessarily accurate – the purpose of the drawing is to simulate the displays and emphasize the difference in number of pixels between the various resolutions. First rectangle represents your old TV with a resolution of 640×480 pixels. Note how large the pixels are. The other two rectangles represent displays with 1280×720 and respectively 1920×1080 pixels. Note how much more pixels fit into the same area in the case of the last two displays (rectangles).
In the above image we have shown the difference in pixel size for the same area in the case of three resolutions. Let’s also see the difference in size between the resolutions if we would keep the pixel size constant:
The image above really makes stand out the differences between resolutions. As you see there is quite some difference between 720p and 1080p, however don’t hurry to take any conclusions whether or not 1080p is better than 720p – we will discuss this at the end of the guide when we have all the information we need in order to take the right decision.
Why and When Resolution Matters
The higher the resolution is the more detail it fits into a given area (like the TV screen). If on your old SDTV (Standard Definition Television) you would see the actor’s eye, on a HDTV (High Definition Television) you would actually see the wrinkles around his eye and his eyelashes. Resolution is not the most important factor in defining a HDTV picture quality. Contrast ratio and saturation are more important for the overall viewing experience. But let’s see why resolution matters. The best way is to use pictures again. We have below two images that simulate two TVs with different resolutions. The image on the left has a higher resolution than the one on the left. As you see the image on the left looks very good compared to the one on the right. The image on the left side doesn’t look perfect though. Let’s make this exercise: make one big step away from the monitor and note the difference, then make two more big steps away (i hope you have enough room) and note the difference again.
As you see, when you are sitting close to the monitor (at the normal distance) the image on the left doesn’t look very well and the one on the right looks very bad. If you make one step behind, the image on the left looks much better but the one on the right doesn’t yet look as good. Then, if you get back enough you will see that both images look pretty much the same. The exact thing happens with TV watching. If you sit to close you will not like how the picture looks. If you sit at the optimal distance the image will look good. If however you sit too far away you will loose the advantage of the high resolution and you will get pretty much the same detail as from a lower resolution TV.
Video Source Resolution Matters a Lot
I would say that the resolution as well as the quality of the content (video signal) is almost more important than the resolution of your HDTV. No matter how good your HDTV is, it will not be able to make up for the lack of detail or quality in your video source. That is, if you are watching SD content on your HDTV it will look as bad or even worse than on your old tube TV. You get the most detail from a movie by using a 1080p video source (like a HD DVD or Blue Ray DVD player) together with a HDTV that has the native resolution of 1080p. High definition TV broadcasts will look very good, way better than the old standard definition content. Regular DVDs will look better but not as great as high definition ones. SDTV will look as bad as before or even worse. It’s important to keep in mind that the source quality and resolution is as important so you don’t expect your plasma TV to do miracles and feel disappointed.
1080p vs. 720p – Is 1080p Worth the Money?
The answer is not an easy one and it has to do more with YOU than with the TV itself. This is a decision only you can make. There are three factors that you must take into consideration when asking this question:
- TV Size
- Viewing Distance
These are three factors that determine how much detail you actually see. The farther away you sit and the lower the resolution is, the less detail you actually see and the TV or HDTV needs to have. One important note to make is that the resolution which matters is not really the maximum resolution your HDTV supports but the one of the actual content you are viewing. To be more specific, if you watch regular SDTV (480i) on a 50 inch plasma TV that has a native resolution of 1080p, and you sit at the optimal distance for 1080p resolution, the content will look awful. If however you are watching a high definition movie on a HD DVD or Blue Ray, and you sit at that optimal distance, you will have an amazing experience and you will see all those little details.
So you have to ask yourself what type of content you will be watching. If you never intend to watch HD DVD or Blue Ray movies at full 1080p resolution and what you want is to watch just TV broadcasts (even if they are HD) and regular DVDs then 720p is probably enough. Also if you sit too far away from your plasma TV you may not be able to perceive the full detail of 1080p even if you are watching HD DVD or Blue Ray movies. Read the Plasma TV Size and Optimal Viewing Distance guide to see in more detail how the three factors affect what you actually see and figure out what is the optimal viewing distance for each plasma TV size and resolution. You can use the calculator available on that page to find out either the optimal viewing distance for a certain TV size and resolution, or to find out what size and resolution you need for the best experience given a certain distance. Note that the chance you will be sitting exactly at the optimal viewing distance is very small. So if you are a bit further there’s no problem, you will not get the full 1080p detail but you will get more than 720p would offer you.
With all that considered I still recommend 1080p resolution. Why? At some point in the future 1080p may and probably will be used to broadcast TV channels. More than that, if you buy a plasma TV and you don’t watch a HD DVD or Blue Ray movie on it it’s a shame. Even if you won’t buy a HD DVD or Blue Ray player from the start there are great chances you will in the future – especially when the war between them will be over, the industry will adopt one of the standards and many movies will be released in one of these formats. Now you might think that you sit way too far away from the TV for 1080p to give you any real benefit. That’s not really a problem for our imaginative minds though. You can just pull yourself a chair and watch a 1080p high definition movie exactly from the distance you like. It isn’t even a complicated thing. Just get a chair and you have the perfect setup 😉
I told you it’s not an easy answer. And I didn’t even bring on the price factor :). 1080p TVs are more expensive than the 720p ones. I had to mention this. It’s probably one of the most decisive factors for many people. And I recommend you to put more weight on overall picture quality than on resolution when you buy a plasma TV. When you have to choose between resolution and color saturation, contrast ratio or black levels choose the latter. One of the best plasma TVs in the world is a 720p Pioneer. That’s right. It’s “just” 720p but looks better than many 1080p competitors. It’s also pretty expensive however :).