Is Your HDTV Under Performing? Here’s a Fix

May 11th, 2012 · 12 Comments · 3D HDTV, DLP, Laser HDTV, LCD Flat Panel, LED LCD Flat Panels, OLED, Plasma

Every TV has one: a button that zooms in on the picture, or changes the aspect ratio. Sometimes called View Mode, Format, Size, Zoom, or something similar, these modes have a variety of names, but all have the same purpose.

In reality most of the time there is only one “correct” mode, the other modes offering less resolution, possible artifacts, and in a few limited cases, a better picture.

Overscan

One of the primary reasons why these controls exist is a “feature” called Overscan. In the olden days, TV makers had a lot of wiggle room in defining the edges of the image. So two TVs, of the same size, might show slightly more or less of the broadcast image. At the edges of the image, there was frequently a lot of noise (so of which was part of the image, some not).

Even in the early days of HD, many stations broadcast a few pixels of noise, so a TV was better off showing, let’s say, 1,900 x 1,060 of the original signal, then blowing it up to fill the 1,920 x 1,080 screen.

And that “blowing up” is the problem.

Scaling

Every pixel on your TV is active, regardless of the resolution of the source. With DVDs, the TV upconverts, (also known as scaling) the image to fill the screen. It is creating information that is not in the original source, in order to have data for every pixel.

To a lesser extent, the same is happening when you view an HDTV with any amount of overscan active, or when in one of the modes listed earlier. The TV is zooming in slightly on the original image, which requires it to modify every pixel in the image to fit. Look at it this way, if you’re watching a Blu-ray, or a 1080i image from cable/satellite, that image has a specific pixel for every one of the actual pixels on your TV. A 1:1 map, if you will. If the TV has overscan active, or is zooming in slightly, now it’s more like a 1:0.9 map. The TV has to scale the image.

Here’s an example. Compare this image to the one at the very top of this article:

Notice how you lose a little on the edges, the car at the bottom is barely visible, the building at the top is right at the edge of the screen (click here for the two images side by side).

Regardless of how good the scaler is in the TV, this is going to increase noise and artifacts, and potentially reduce resolution (if it can’t scale the image well).

Find this control on your TV, and for the best picture, set it to Just Scan, 1:1, Full, Native, Dot-by-Dot and so on. You’ll be able to tell which is the right one, as when you’re watching a 1080i or 1080p image, it will appear to zoom out slightly, and you’ll see more of the picture’s edges.

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A few exceptions

Occasionally, you’ll find a channel or program that has some weird, non-picture data on the edge of the screen, usually only a few pixels wide. If this bother’s you, well, now you know where the control is to zoom in and clip it off. This is pretty rare, these days.

One other use for this control is zooming in on a 16×9 image that resides in a 4×3 window. For example, on my AT&T U-verse, BBC America is only available in standard definition (thanks a lot AT&T). So if I want to watch the 16×9 Top Gear it’s only viewable with black bars on the sides (SD is 4×3) and on the top and bottom (because it’s 16×9 within the 4×3). Obviously I don’t, I buy the show in HD on iTunes, but you get my point. In this case, you could zoom in on the image, to better fill the screen with the tiny program. Keep in mind, this will likely look like crap.

A 16×9 image within a 4×3 window (note, I increased the brightness of the image so the borders were easier to see):

A 16×9 image within a 4×3 window, zoomed (note the loss of picture quality, even at this resolution).

However, and this is a HUGE deal, you should only be doing this rarely and for the few channels not available in HD. If you are doing this a lot, especially with network shows, you are likely not set up correctly for HD. Check out my article on How to Understand Aspect Ratio.

If you’re black-bar-ophobic, there are often modes that stretch the entire 4×3 standard definition image to fill the screen, or the more clever of these modes that keeps the center of the image the correct aspect ratio, and only stretch the edges. It’s worth noting that using either of these modes is quite possibly the worst your TV will ever look, and should be avoided if at all possible.

For example, here’s the same image above, but stretched horizontally (for a side by side with the full image, click here):

This is really noticeable with people. Here’s a full 1:1 image:

And a stretched 4×3  image (click here for the full version):

This is almost always the default setting for TVs in hotels, which is one of the main reasons hotel TVs look so terrible.

Source Boxes

All cable/satellite boxes and Blu-ray players have aspect ratios settings too. The wrong setting will provide a distorted, lower resolution image. Most on-screen menus ask you to select your TV aspect ratio. For all current HDTVs this would be 16:9. If set to 4:3, the image will be badly distorted. (as shown in the faces image above). Make sure your source box is set to the 16:9 image setting.

Most boxes will also ask for an output resolution setting. Choices will  include 480i, 480p, 720p and 1080i. With 1080p TVs (most current models), this control should be set to 1080i (some cable/satellite boxes also allow 1080p output, but it only applies to pay per view movies).

Blu-ray players should be set to 1080p. Many offer a 1080p/24 setting, though not all TVs can do anything with this framerate. Most Blu-ray players will have a test mode to verify that your TV can accept the resolution prior to making the final setting.

If you have a 720p TV, you can set the cablebox to either 720p or 1080i, though the latter is probably better. If you choose 720p, the signal will be ideal for 720p content such as ABC and Fox but 1080i content (used by CBS, NBC, HBO and others) will be down converted in the box. It’s likely your TV will do a better job de-interlacing and downconverting 1080i content than your cablebox, so choosing 1080i output is likely better. Also, most non-1080p TVs these days are actually 1,024 x 768, slightly more vertical resolution than 720p. So you may squeeze a few extra lines of resolution when watching 1080i content by choosing the 1080i output.

Conclusion

The short version? Ideally you’d watch all HD content set to fill the screen, with no overscan. Check your settings, there may be aspect ratio controls, and separate overscan controls. While most Blu-ray players will auto-detect the correct aspect ratio (nearly always 16×9), DVD players and cable/satellite boxes do not. Check the settings of these as well to make sure they’re sending your TV the correct aspect ratio (and resolution!). I always watch TV with the overscan off and in a 1:1 pixel mapping mode, and it has been years since I’ve seen noise on the edges of the screen. Check both controls, your TV may look  better… for free!

 

Geoff Morrison @TechWriterGeoff
Geoff’s book is now in paperback

 

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12 Comments so far ↓

  • tech engineer

    LOL What a great deal HD is. Claims of a higher definition picture which often a person cannot see any better than non-HD and with about a large, 25 percent LOSS in the screen size. And to fix it, the users often make the picture blurry. Sounds like technology that only makes money for the sellers of it. This has been a MESS in progress!LOL What a great deal HD is. Claims of a higher definition picture which often a person cannot see any better than non-HD and with about a large, 25 percent LOSS in the screen size. And to fix it, the users often make the picture blurry. Sounds like technology that only makes money for the sellers of it. This has been a MESS in progress!

  • kay roth

    RE: 52″ Samsung (4 years) picture was unclear in one corner and has gradually spread across the screen. At first the corner was bad then cleared but now it remains unclear. Predictable or is it dying? Thanks

  • kay roth

    Re:52″ Samsung (4 yrs) picture started to be unclear in one corner. It has now spread across entire screen. Should something be reset or is it dying? Wish I could explain more specifically. Thanks

  • Renny

    I have a 32″ Samsung TV and the resolution has been decreasing for some weeks. First of all there were slight lines in the picture then definitive RGB lines. When I switch the TV on the picture is fine and clear but after a minute it’s like an old tv and warms up to the problem, now the picture has a white mist over the whole screen! Can any one suggest any settings I can change or is the TV on its last legs?
    Thanks in advance

    It sounds to us like a part is failing. To verify, try connecting a different source such as a Blu-ray player, and to a different HDMI input. If it doesn’t change after the TV is warmed up, then your original source or that input may be going bad. Trial and error is the best method to determine which component is the one.

    1-800-Samsung can also help you troubleshoot your TV

    HD Guru

  • Rosa

    I am having difficulty with my Sharp LCD tv ( LC-19SK24U) I think I know what the problem is, but I don’t know how to fix it. The screens reads “not compatible with this signal.” I’m pretty sure I messed it up trying to change the resolution to 1080. It was 480. I had this problem when the Directv was installed, but I was able to fix it, but can’t remember how. Ideas?

  • adam

    a question probably asked many times, but if you have a 720p tv, should you set your bluray player to output at 720p and then allow the tv to scale to its native res? Or, set the output to 1080p and allow the tv to scale down so image scaling only happens once not twice?

    If its a 720p TV we recommend setting your source boxes for 720p this would include cable/satellite box as well as your blu-ray player .

    For 1080p TV we recommend 1080i or p output setting of the source devices (some TVs only permit 1080i source input)

    HD Guru

  • John

    Hey HD Guru, I have a question regarding my Panasonic 42ST30 plasma and the HD size setting under aspect ajustments.

    I have my Optimum HD Cable box(Samsung model SMT-C5320) picture format set to send the HDTV a 1920 x 1080i normal signal. If I was to use a HD Size 2 (1:1) setting 100% of the time—which usually always snows a thin line at the top or side—would that eventually cause a thin Burn-in line on my Plasma? Only way to fill my entire screen 100% using cable is with HD Size 1 (95% of HD images).

    Using custom mode with the aspect adjustments

    The lines you see are are a normal part of some HDTV signals. We do not see them on all channels and we simply ignore them whn we do. I have not seen any signs of burn-in due to this on any broken-in plasmas we’ve used. If you enlarge the image it cuts down on fine resolution due to aliasing. Your call on the mode or just enlarge to Size 1 when they appear.

    HD Guru

  • Stan S.

    I love this article. I’m going to send it to my cousins who have several hdtvs, none of which are set correctly. Have to bite my tongue when I visit. as for the hotel settings, it’s the first thing I change. I simply don’t understand why bother with HDTV in the rooms if they won’t pay for HDTV broadcasts.

  • Sam

    So how does this model differ from the one Costco has for sale:
    LC-80LE633U
    http://www.costco.com/Browse/Product.aspx?Prodid=11758383

    I assume the Costco version is just “re-branded” for Costco only?

    The LC-80LE633U adds a scanning backlight to its 120 Hz refresh, Sharp calls this Aquomotion 240 although the TV still produces a total of 120 frames per second (Hz)

    HD Guru

  • Michael Chen

    A nice article, but unfortunately the simulated images don’t quite do justice to what you are talking about. I did a similar article late last year on the same subject matter and got down to what the degradation actually looks like in the image.

    Readers may find that the images will be a compliment to the issues you refer to here. The article can be found over at the TLVEXP.com site.

    Regards

  • chew

    Well hdguru thanks for info,i only watch hd channels on my tv, my home theater reciever upscale everything to 1080p anyway,i have very clean and sharp picture,plus i have a plasma,thats makes a difference.

  • Stringfellow

    Fascinating! Thank you, so kindly, for this post. I really thought I was the only one who realized that the “Full” on my SONY gave me the entire 1080 by 1920 pixel area to work with.

    HDGURU, similarly to your issue with AT&T U-verse’s non-HD broadcast of BBC, I have had an issue with Verizon FiOS not broadcasting Cartoon Network in HD. For the new ThunderCats TV-Series, I have to zoom the image in to preserve the image so it does not look stretched. When it was being stretched automatically by my FiOS DVR box the image looked a great deal grainier and unclear. I am not clear why FiOS does not have Cartoon Network HD, but I hope they eventually get it.

    Again, I am glad you spelled it out in detail with the examples so that people have an opportunity to improve the performance of their viewing.

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