screen is very dim on led backlit lcd panel price

For the video display developer LCD panels are available in many sizes and resolutions, they are also available with many choices of maximum brightness. The following considers the topic of LCD panel brightness, the choices, the methods for adjusting brightness and some brightness adjustment scenarios.

LCD panels are generally rated as to their maximum brightness level which is expressed in Nits, it is equal to Candela/sqm (cd/m2), and this will be at a particular color temperature as noted in the specification, usually 10,000 K. In terms of a practical understanding, the following is a rough guide:

Outdoor displays range from a low end of 700 nits to typically 1,000 or 1,500nits and up with 2,000~2,500nits and even up to 5,000nits seen with some models. This may include standard LCD panels, custom LCD panels as well as custom cut LCD panels.

Virtually all LCD panels have a LED backlight these days, these are powered by an LED driver board. Brightness control via the driver board will be by one of two methods:

PWM (Pulse Width Modulation): This varies the duty cycle of the backlight “on time” – it is predominant in modern LCD panel LED backlight designs to enable support for digital brightness controls.

Analog: Uses a simple variable voltage to adjust brightness, for example this might be a dial or slider type potentiometer / variable resistor. To see how to enable analog backlight adjustment visit: https://www.digitalview.com/blog/brightness-adjustment/

One of the advantages of LED for the backlight is the range of adjustment that is possible, however it is important to note that the range varies significantly from model to model. Some industrial panels can be turned to very low light levels making them suitable for use in special environments such as at night. Lower cost panels limit the range of brightness to what might be required for typical usage, whereas panels with full range dimming from full off to full on require more complex backlight drivers.

Backlight lifetime: Many LCD panels have a backlight lifetime rating of 50,000 hours (typically measured to half brightness), this can be extended by running the LED backlight at a lower brightness level. Some panels may only offer 30,000 hours as a lower cost solution while other panels may offer up to 100,000 hours for high end applications.

An LCD panel backlight may be constructed so the LED’s are mounted directly behind a light guide diffuser, or they may be mounted along one or more edges of the light guide.

Active backlight: This is a function of some LCD panel backlights to automatically adjust the backlight brightness in response to the image. For more advanced systems there is an LED array making up the LED backlight, this adjusts the brightness in areas localized to the image being shown. This can greatly enhance the brightness across the display and is being used primarily with video, for example on consumer TV sets. It is not useful to all image types, for example a spreadsheet or content like maps or data is not likely to benefit.

Local dimming: Some LCD panels with direct LED may support local dimming so the LED’s are dimmed in response to the image close to them. This will not be at the same resolution as the LCD panel itself but will help greater contrast over the display by enhancing the brightness in bright areas of the image and darkening the image in dark parts of the image.

Both of the above techniques are likely to be more beneficial to certain types of content than others. For example a movie is likely to benefit more than a spreadsheet.

For the LCD monitor manufacturer it is important to consider that any covering over the LCD panel will reduce the brightness. For example the protective glass over a digital signage display, or a touch screen, or a semi-silvered mirror. So if a specific brightness is required the measurement should be taken with these in place.

There are various relatively low cost brightness meters available, typically in the couple of hundred dollars range. It is difficult to comment on the accuracy of these but we have found them to be within 5% of each other, though more importantly they do appear to be quite consistent in measurement so good for measurement comparisons. For more accurate measurement there are light meters from companies such as Minolta that can be calibrated, the cost may run into several thousand dollars.

Examples of light meters costing a few hundred dollars include SpyderX by Datacolor (needs a PC), a handheld meter is the SM208 by Sanpometer (search SM208 meter). Note: Many light meters, including smartphone apps, will be meters used for photography and not give readings in nits (or candelas). LCD panel specifications are typically measured using nits.

PWM and Analog: Most Digital View LCD controllers support PWM and Analog as a method for adjusting the backlight brightness level (this is noted in the column headed “Other” on the controller board summary table: https://www.digitalview.com/controllers/lcd-controllers-home.html. Also see https://www.digitalview.com/blog/brightness-adjustment/ for a guide to using a dial or slider type variable resistor to adjust the backlight.

DPMS (Display Power Management System): The backlight will be automatically turned off after a period if there is no valid video signal being received.

Ambient light sensor: The backlight is adjusted for brightness or powered off depending on ambient light conditions. This uses a light sensor attached to the LCD controller board, see https://www.digitalview.com/blog/light-sensor-app-note/ for more details.

The specifics of the backlight control are documented separately for each LCD controller model (product summary here) in the product manual available for download on the product page.

Note: There are two ways to adjust the perceived brightness of a LCD panel or LCD monitor, the backlight and the black-level. Very often, particularly in the past, the monitor brightness setting adjusted the black-level, this adjusts the LCD but not the backlight.

Color, color temperature etc: In addition to adjusting the brightness other settings may be adjusted as well. For example the color temperature or for example a switch to green monochrome for night vision.

Auto-dim if lights dimmed for a projector. This might be triggered by a command from a room sensor or automatically by an ambient light sensor (Autobrite+).

Night-safe lighting (update) : Dual-rail backlights can also be supported. These special backlight enable normal brightness and extreme low level brightness with custom night-safe lighting. Contact us for details.

Note: We have a blog on methods for implementing an ambient light sensor with Digital View LCD controller boards to automatically adjust the backlight or system power, see: Ambient Light Sensor

Update March 2019: Most of the above remains unchanged except for the increased availability of high bright LCD panels of around the 1,000 nit to 2,500 nit range. AUO for example has a number of large size LCD panels with 1,500 nit brightness for the digital signage market. Tianma has panels under 20″ with 1,000 nit to 1,500 nit brightness for various outdoor applications.

The other change is that high bright panels are now increasing edge-lit, this makes the panels thinner and these panels tend to use less power than the previous models. One of the benefits for monitor designers is easier heat management and reduced overall display system costs.

I have researched this problem and found that it does indeed indicate that some hardware components may be bad. The following solution seems to be effective in most cases, but it requires very fine soldering skills:

They sell the components mentioned as a kit on their website which consists of the coil, an "IC" (really this is just a diode), and 3 "filters" (capacitors). They have an excruciatingly detailed video showing how to change these parts, but the right soldering equipment is essential. They also list this kit on Ebay - search for "iPhone 5 backlight coil".

Traditional LCDs use CCFLs, or cold-cathode florescent lamps, as their backlight. While cheap, they"re not as energy efficient as LEDs. More importantly, all contain mercury, and aren"t able to do some of the fancy area-lighting of which some LED backlit models are capable. Because of these issues and the falling prices of LEDs, CCFL backlit LCD TVs will disappear entirely very soon. In 2013

Most LED LCDs on the market today are edge-lit, which means the LEDs are in the sides of the TV, facing in toward the screen. In the image at the top, the LED strips are above and to the side of this exploded-view of an LCD panel. There"s a close-up view here (full article with more images

There are a few models that are have their LEDs arrayed on the back of the TV, facing you. These are less common, though are making a comeback in the form of cheaper, but thicker, mostly low-end LED LCDs. There are a handful of high-end TVs that use full-array LED backlighting in a slightly different way, which we"ll discuss later.

Because the light is brightest nearest the LEDs, it"s common for edge-lit LED LCDs to have poor uniformity. This is especially noticeable on dark scenes, where areas of the screen will appear brighter than others. Corners or edges can have what looks like tiny flashlights shining on the screen. Check out

Each manufacturer has a preferred method for edge-lighting, but some models may feature one type, while other models feature another type. Generally speaking, the fewer LEDs the cheaper the TV is to produce. Fewer LEDs also mean better energy efficiency, but LED LCDs are already so efficient that this is a tiny improvement. Unfortunately, specific details about where a TV"s LEDs are located (beyond "direct" or "edge"), the number of LEDs, and other useful information about the backlighting, are rarely listed on a TV"s spec sheet.

The biggest difference between all the LED back/edge-lighting methods is how effective their "local dimming" is, which as you"ll see, has become a pretty broad term.

This design has all the LEDs along the bottom of the TV. Though manufacturers don"t like to reveal how many LEDs they use, this is likely the type with the least number of LEDs.

Though TVs of this style claim to have "local dimming" you can see how this is a pretty broad definition of "local." Even if each LED is dimmable independently (highly unlikely), you"re still only able to dim columns that stretch from top to bottom. Something like this:

As you can guess, this design has LEDs on the top and bottom edges of the screen. The local dimming here is a little better, where the zones can be slightly smaller areas of the screen, like this:

This is a less common method now, as it requires more LEDs than any of the other edge-lighting methods. The local dimming can get a little more accurate, but is still limited to large-ish zones. If we used our moon example image, the result with an all-sides edge-lit would look just like top and bottom. But with regular video (that has more light sources than just the moon), it will have a more zones to work with, sort of like this:

All Sides used to be the most common edge-lighting method. But as the light guides improved, and costs had to come down (to make cheaper LED LCDs), this method became fairly rare.

Nearly all "backlit" LED LCDs use this method. The LEDs are arrayed on the back of the TV, facing you, but there is no processing to dim them individually. They work instead as a uniform backlight, like most CCFL LCDs. The least expensive LED LCDs use this method, as do most of Sharp"s

This is the ultimate LED LCD, offering performance that rivals the better plasmas. Like the "direct-lit" TVs, these have their LEDs behind the screen (the image above for direct-lit works as a visual aid for this type as well). The full local-dimming aspect means the TV is able to dim zones behind the dark areas of the screen in fairly specific areas to make the image really pop, drastically increasing the apparent contrast ratio.

However, they basically don"t exist. The LG LM9600 wasn"t great last year, and LG has yet to announce any full-array local-dimming TVs for 2013. The only other local-dimming LED LCD was the Sony HX950, which was excellent, and is still current. In his review David Katzmaier called

The two biggest-selling TV makers in the U.S. are Samsung and Vizio, and neither has sold a full-array local-dimming LED TV for the last couple years. At CES 2013, Samsung"s only such TV announced was the insanely-expensive E420i-A1, saying "Sure, black levels get darker, but the trade-off in shadow detail is one I"m not willing to make," and concluded that its "local dimming does nothing to improve picture quality."

As I mentioned at the top, there"s no easy way to tell, just by looking at a spec sheet, what kind of backlight a TV has. By extension, there"s no way to tell how good its local dimming will be. Bad local dimming can, at worst, just be marketing hyperbole. At best, it does little to improve the picture. Good local dimming, however, can make a punchy image, with lots of apparent depth and realism. Or to put it differently, the best LCDs on the market have the best local dimming, allowing them to rival plasmas on the picture quality front. The better TV reviews, like ahem those here on CNET, will talk about all this, so you"re not duped into paying for a "feature" that"s little more than a check mark on a spec sheet.

Got a question for Geoff? First, check out all the other articles he"s written on topics like Send him an e-mail! He won"t tell you what TV to buy, but he might use your letter in a future article. You can also send him a message on Twitter: @TechWriterGeoff.

One of the top buzzterms in LED LCD marketing is "local dimming." Ostensibly, local dimming can dim the area of the screen that needs it, while keeping the bright parts of the screen bright. This technology can really increase the contrast ratio to make a better image. It"s also vital to get the intense highlights possible with High Dynamic Range (HDR) content.

LED LCDs don"t have the OLED (or plasma, may it RIP). As such, their images don"t have quite the depth and three-dimensionality that"s possible with other technologies.

This is the full monty. The name refers to an array of individual LEDs behind the LCD panel, all pointing out through the screen toward your eyeballs. A mock-up example is shown at right, if the front LCD layer was removed and the LED backlight exposed.

While individual control of all these LEDs would be ideal (though rarely implemented), the most common method is a set number of "zones." Depending on the TV, these could number in the dozens or more. Unfortunately, most LED TV makers don"t disclose the number.

Each zone is responsible for a certain area of the screen. Objects smaller than the zone (stars in the night sky, for example), don"t benefit from the local dimming, and can look muted as a result. Also, if a zone is lit, and an adjacent zone isn"t lit, you could see a halo/bloom as that part of the screen becomes brighter than its neighboring zone. This artifact is commonly known as "blooming."

At its best, full-array backlit local dimming produces the best images you can get with LCD. It"s also always more expensive than TVs from the same company with one of the other backlighting methods discussed below.

The downside is size and cost. The LEDs have to be set back from the screen a little (the farther away, the fewer you need to cover the same area), so there"s additional depth compared to the edge-lit models.

Local dimming, in this case, becomes a bit looser of a term. Yes, the TV can still dim areas of the screen, but those areas are much larger than they are with full array, as you can see in the image above.

Worst-case, the "local dimming" could be nearly invisible, or dim huge swaths of the screen at a time, neither offering any benefit. In some cases, it could result in a worse picture.

Best-case, there"s a noticeable improvement in the picture quality, though not as much as there would be with full array. The pin-point highlights of HDR aren"t possible here, though some models might still offer Wide Color Gamut (which is related to HDR, but separate).

Depending where the LEDs are (along all four sides of the screen, just the right and left, just the top and bottom, or just the bottom or the top), edge-lit local dimming can have widely different performance.

One last trick isn"t really "local" dimming as much as it"s just "dimming," or maybe "global dimming." The entire image will get darker with dark scenes, and stay bright with bright scenes. As in, the entire backlight functions as one single light. This is common among the least expensive LCD TVs.

It"s common on these models, for example, that when given a full black image (like the fade-out at the end of a movie, but before the credits start) the LEDs will shut off completely, making the TV seem like it has a really good black level.

This is fake, of course. If anything should appear, the LEDs kick back on, and the black level jumps up, revealing the TV"s true (and far more muted) contrast ratio. There are some tiny energy-saving benefits to turning off the LEDs, but visually this is can be distracting.

Another variation of this theme senses the average brightness of the scene and, during darker scenes, ratchets down the whole backlight. Again black levels improve because the whole screen is darker, but this is at the the expense of bright highlights. Sometimes this causes visible fluctuations in overall brightness.

It all comes down to "don"t believe the marketing hype," at least not at face value. Local dimming can be a way to get near-OLED levels of picture quality. Or, it can offer some improvement compared with basic TVs, creating a pleasing, if not class-leading, image. Or, it could be a marketing label for something that"s not really much benefit at all. As usual, the best way to know is to check the reviews, where TVs with good local dimming do really well.

Got a question for Geoff? First, check out all the other articles he"s written on topics like why all HDMI cables are the same, TV resolutions explained, LED LCD vs. OLED, and more. Still have a question? Tweet at him @TechWriterGeoff then check out his travel photography on Instagram. He also thinks you should check out his bestselling sci-fi novel and its sequel.

LED-backlit LCD TVs typically come in one of two sub-types of panels: Vertical Alignment (VA) or In-Plane Switching (IPS). VA panels tend to have much high contrast ratios, and therefore better black uniformity. IPS panels, on the other hand, have worse contrast ratios and suffer from more backlight issues that can affect black uniformity, including "IPS glow", which is a kind of "glow" effect that can be seen in the corners of IPS screens.

LED-backlit LCD TVs are prone to black uniformity issues, but OLED TVs can produce virtually perfect blacks because their pixels are self-emitting, and therefore don"t have the same limitations caused by improper backlight implementation. That means they don"t suffer from clouding or flashlighting as LED TVs do.

Poorly designed backlight placement. The type of backlight and its position directly affects the uniformity of the screen. The worst uniformity can be found on edge-lit LED TVs, because the LEDs are only on the edge of the screen. Full-array LED TVs have good uniformity because their LEDs are spread out across the whole screen. Some edge-lit TVs have great uniformity. You can learn more about different backlights here.

Non-uniform frame pressure. Both the LCD screen and the diffuser layers are somewhat flexible. A slight difference in pressure on the frame of the television can change the uniformity of the picture. On some televisions, this can be fixed (see below).

Uneven lighting intensity. Sometimes, the intensity between two lighting components can vary in a set (for example, one LED could be slightly brighter than an LED next to it). This is less likely to happen with a brand new TV but can start appearing over time if some components age and degrade faster than others.

Flashlighting can sometimes be fixed on some televisions. If the flashlighting is caused by pressure from the TV"s frame, you can adjust it by slightly loosening or tightening the screws behind the edge of the screen. Some TVs don"t expose the screws, however, so this won"t always be possible. You should also keep in mind that a small change in the tightness of a screw can have a big impact on the uniformity of the screen, so be careful if ever you do try this step. While this can fix the issue, we don"t recommend it unless you know exactly what you"re doing, as it may cause more problems than it solves.

For clouding, there"s a pretty simple fix that—while not guaranteed—can have good results. Power on the TV and display a black image. This will allow you to see the lighter spots on the screen. Next, take a soft cloth and massage those brighter spots to improve the uniformity. You should only apply very gentle pressure, just barely touching the screen. You can also try a few different stroking patterns. If you are patient enough, this works surprisingly often, especially on edge-lit TVs, although you should be very careful to avoid damaging your screen.

Alternatively, you might consider returning or exchanging your television. Some models are more prone than others to having issues. Even within the same model, some units can have more uniformity issues than others because of slight variation in the manufacturing or shipping process. It can be worth trying to exchange it for the same model before going with an entirely different TV. Extreme cases of clouding are also covered under a TV"s warranty.

Backlight uniformity issues don"t increase over time unless a large amount of stress is put upon the panel (in the case of a big temperature swing, for instance, or if the TV is moved).

Sometimes, just letting the TV settle for a few days after unpacking it can solve the issue. This is especially true if the TV is laid on the side during shipping/moving.

Black uniformity refers to how evenly a TV can display black across the screen, especially when displaying a bright object over a dark background. It’s important when watching dark scenes in a dark room, and while most people shouldn’t notice black uniformity issues like flashlighting and clouding, they can become more apparent when the issues are especially bad. You won’t need to worry about these problems in rooms with lights on, though. For each TV, we take a photo of a black frame to capture the black uniformity, and then we calculate the color values of the pixels to find the standard deviation of the uniformity. We then do the same with local dimming enabled.

You may be able to remove flashlighting (to some degree) by tightening the screws of the TV’s frame. This can have pretty dramatic effects on the picture, though, so you should be very careful when attempting this. For clouding, gently massaging problem areas with a soft cloth often does a good job of fixing bad uniformity. In the end, the safest bet may be to simply return or exchange your TV if you can, since uniformity varies between individual units.

How long will your LED display last? In nearly every industry, from retail businesses to concert halls to corporate centers, decision makers need to evaluate the return on investment (ROI) of their LED signage. In most cases, potential buyers go straight to the obvious place: the LED manufacturer’s spec sheet. The industry standard for LED lifespan is 100,000 hours, or about 10 years, and most people assume that’s how long their display will last. But it’s not quite that simple.

The 100,000-hour figure assumes that every diode will be running at full brightness, consistently — which, on an LED screen, is virtually never the case. The lifespan figure can also be misleading because it indicates when a diode degrades to half-brightness, not completely dark. Many other variables affect an LED display’s lifespan; you can’t rely solely on the number on the diode spec sheet.

“The reality is, your screen can often last significantly longer than 100,000 hours,” says Kevin Izatt, a senior product manager in Samsung’s Display division. “We’ve had displays that have been up for 15-plus years with more than adequate brightness. Because the diode is actually only one factor in the lifespan of your LED display.”

The biggest contributor to diode degradation is heat. As you increase a diode’s brightness, it produces more heat. Your display’s physical environment also contributes to the temperature of the diodes, especially for outdoor displays.

“Let’s say you’re in Vegas — Death Valley. The diode is fine to operate at those temperatures, but it will degrade faster,” says Izatt. “Temperature is a big factor — and not one you have control over.”

The quality of your display’s power supply — and how hard it drives the diodes — can have a significant impact on your screen’s lifespan. The other components being powered, such as fans and electrical components, have their own lifespans as well, which are also impacted by the power supply.

“Fans are mechanical; they break down,” explains Izatt. “And similar to your computer, the electrical components don’t last forever. Together, these factors all contribute to the lifespan of an LED display. Looking at just the diode lifespan doesn’t give you the complete story — almost always, another part will go out first.”

“Something like airflow is very important,” says Izatt. “You need a screen that has good cooling, and a design that allows heat to flow out of the back through vents.”

It’s easy to see why: The circuit boards powering the display release heat, and that heat needs to go somewhere. Without a strong design, thermal stress will degrade the life of the display, except for the highest-quality parts — optimal conditions notwithstanding.

“Lots of variations on the color and brightness you use will impact the life of the diode,” explains Izatt. “For instance, black doesn’t use any of the diodes at all. And if your content is using lots of gray, that’s a much lower power output than white.”

That’s not to say you should hold back on displaying rich, vibrant colors — after all, that’s what LED does best. But it does factor into your product’s life expectancy.

To help businesses transition from LCD to longer-lasting LED signage, Samsung has launched a trade-in program. Samsung will come on site to remove your existing display and provide a discount on a new LED bundle kit.

Traded-in LCD displays that are still operating will be refurbished and resold, and your business will receive a cash rebate. Nonworking displays will be recycled and their parts reused.

You can’t rely on the number on the diode spec sheet; the lifespan of your LED display depends on many more factors. “Overall quality has a tremendous impact on the life of the display that diode specs just don’t take into account,” says Izatt. Your best bet is to look at the purchase holistically and invest in a top-tier product.

As you plan your LED signage rollout — or an upgrade — learn how to configure and tailor your screens’ real-time messaging with an integrated CMS in thisfree guide. And if you haven’t decided what kind of display is best suited to your current project, compare all ofSamsung’s LED displays.

After a long, hard day, you finally sit down to catch up on your favorite show. But when you hit the power button on your remote control, your TV screen stays black! You try pressing the remote’s power button again and again from every angle, but still, your TV has no picture. If this sounds familiar, you’ve likely fallen victim to one or more TV screen issues.

What causes a TV screen to go black? Software issues, loose connections, or backlight problems are usually behind black TV screens. Learn about each of these causes and get tips for troubleshooting them so you can get back to relaxing with your favorite TV shows, movies, and video games.

If your TV screen is black and there’s no sound, you’ll want to check for an LED light or a small indicator light that tells you the TV has power. If there is no power to the TV while it is plugged in, there may be an issue with the outlet or fuse box in your home. However, if the TV is on but the screen is black, the problem could lie with your TV’s software.

Unplug the TV from the wall, and, if possible, remove the power cord from the back of the TV to perform a soft reset. Wait 30 seconds, and plug the TV back into a working outlet to test it again. If you’re still having screen issues, you might want to bring in an expert — they’ll know how to fix your TV’s black screen.

If your TV screen goes black but the sound still works, the first thing to check is the input source to ensure it is turned on and operating correctly. This includes external devices like cable boxes, video game consoles, laptops, and streaming devices. Once you’re sure the input source is working properly and you have the right input settings, check the cable connections. In many instances where the TV screen is black but the audio works, poor cable connections could be the issue.

Whether you’re working with an HDMI cable, RCA (usually yellow, white, and red cables) set up, or another type of connection, you need to ensure the cables are seated properly and firmly into their connection ports. With a good connection, the cable shouldn’t feel loose or easily disconnect when pulled on or moved around. If all your cables have a snug fit but the problem persists, try connecting the device to another TV. If your TV screen is still blacked out, you may need new cables.

Some TV displays, such as LCD screens, use a backlight to illuminate the picture. If the backlight burns out or stops working, it will result in a blank TV screen.

To check your TV’s backlight, make sure your TV is on. Then, turn off the lights in the room and shine a flashlight on the screen. If you can see a picture with the flashlight, then your TV’s backlight is likely burnt out.

While you might be eager to learn how to fix a black-screen TV, a broken backlight does not come with an easy solution. The backlight will need to be replaced, and it’s best to get help from a professional with this task.

If repair costs are outside your budget or not worth it considering the age and condition of your TV, you may want to consider upgrading to a new smart TV. When you purchase a new TV from your local Rent-A-Center, you’ll enjoy free product service and repairs for the life of your agreement as part of our Worry-Free Guarantee.

You’ve run all the tests, checked all the ports, and ensured your TV has power, but your TV screen is still black! There could be a more complicated (and expensive) issue, so it might be time to ditch your old TV for an upgrade.

Rent-A-Center makes it easy to own a new TV, like an LG 65″ 4K UHD Smart TV. From OLED to QLED, we’ve got ultra high-definition TVs with picture quality so crisp, you’ll wonder why you didn’t upgrade sooner. Avoid the headache of your old TV, and shop your favorite TV brands online today. You can even get same-day delivery on qualifying purchases in select areas!

LCDs don’t emit light on their own and must instead have a backlight that shines through the LCD material to display an image. Today’s LCD-based displays use a number of LEDs for the backlighting. To achieve a greater contrast ratio than a standard dynamic range display, the LEDs in the backlight change their brightness level, allowing the display to dim the backlight for darker blacks and brighten it for brighter whites, which creates a wider contrast ratio. There are several different dimming designs that can be used in the backlight to accomplish this.

Global Dimming: The backlight, which consists of a string of LEDs on one edge of the LCD panel, is treated as a single “zone” and is dimmed for dark scenes and brightened for bright scenes. This is the least expensive type of dimming and can be accomplished with a standard LCD panel. This approach works well for scenes with a limited dynamic range. This type of dimming is typically found on notebooks as it has the lowest power consumption of any dimming technique and generates the least amount of heat. The disadvantage of this design is that the simultaneous contrast ratio is never greater than the contrast ratio of the LCD panel, usually around 1000:1.

Local Dimming: This represents a wide variety of different sub-designs, each detailed below. What differentiates all of the local-dimming designs from global-dimming is that global dimming has a single backlight zone, the entire screen’s backlight is adjusted as one control, in local dimming the screen’s backlight is split into segments which can be independently adjusted.

1D Local Dimming: This design also uses an “edge-lit” string of LEDs, but in this case groups of LEDs on the string can be independently controlled. For most displays, the string of LEDs is located at the bottom of the panel, resulting in a number of vertical zones, equally spaced across the horizontal edge of the display. An edge-lit LED string typically contains between eight and sixteen LED groups, resulting in eight to sixteen dimming zones. This design allows for simultaneous contrast ratios of 6,000:1 to 100,000:1. 1D local dimming is currently the most common design found in HDR televisions and displays.

1.5D Local Dimming: Similar to the 1D local dimming, using edge lighting. However in this design an LED lighting string exists on two sides of the panel, typically top and bottom although left and right designs also exists. The advantage of this design is that it typically has 2×16 zones, so twice as many zones as 1D, but more importantly the top and the bottom of the screen are independently controlled, versus the 1D design where each zone is typically the full vertical height of the screen.

2D or Full array local dimming (FALD): In this design the backlight LEDs are moved from the edge of the panel to the rear of the panel and are arranged in a two-dimensional matrix of LEDs. Each LED is independently controlled and adjusts the brightness of just one “square of a checkerboard” on the display, although typically they are rectangles rather than perfect squares. Today’s HDR displays and televisions typically have between 384 and 1152 zones. These designs are the most expensive, due to the complexity of the circuitry and the processing demands required. The design can also generate a large amount of heat, and often requires cooling fans and/or heat sinks to be placed behind the LCD panel to draw heat away from the display electronics. Full array local dimming produces the best image quality of all of these designs and can achieve simultaneous contrast ratios of 20,000:1 to 500,000:1. Due to the high cost of this design, these displays command the highest prices and typically cost thousands of dollars.

Active-dimming: is the term VESA adopted for one of the new tests in our Certification Test Spec v1.1 (CTS v1.1) where we added a new kind of validation procedure to ensure that displays were actually dimming the backlight based on real-time analysis of the video content, rather than merely only dimming when metadata changes occurred in the video stream. It would be typical that during a movie or game that the metadata for HDR10 would not change, however each frame may have a different peak luminance than the prior frame, and thus could adjust the backlight accordingly. This yields better power saving, and better HDR blacks. The new tests in CTS v1.1 ensure that we test, without changing the metadata of the signal, a dramatic reduction in peak luminance from a full-white checkerboard, to a checkerboard where the white boxes are only 5 cd/m2, this provides ample opportunity for the dimming algorithm to reduce the backlight power. When reducing the backlight power the black level of the black segments of the checkerboard will also reduce, and this is what is measured and used in our calculation of active-dimming stops, (for the more technical, “stops” originally used in photography are a power-of-2 logarithmic function).

Hi guys, i"ve been looking around at several forums, not just this one to see if there is a solution for the dim / dark screen issue which seems to plague dell inspiron 1545, 1537, etc. I have seen people change motherboards and say it"s fixed, and some simply refit the video cable to fix, but i now have 3 of these on my workbench and all have the same problem. i have fitted new cables, new inverters, even a supposedly working motherboard to no avail. I even borrowed a working 1545 laptop and tried the cable, screen and inverter from a broken one just to isolate the problem and they didn"t work on it. The real pain is that the original working components didn"t work now either. :emotion-9: Now i"ve got 2 customers machines and a friends machine all with dim screens.

Anybody got any real answers to this issue, are there any Dell engineers out there that must have faced this issue? Need a definate solution before i throw more money at the problem.

The Hisense U8H matches the excellent brightness and color performance of much pricier LCD TVs, and its Google TV smart platform is a welcome addition. But it’s available in only three screen sizes.

The Hisense U8H is the best LCD/LED TV for most people because it delivers the performance of a much pricier TV yet starts at under $1,000, for the smallest (55-inch) screen size. This TV utilizes quantum dots, a full-array backlight with mini-LEDs, and a 120 Hz refresh rate to deliver a great-looking 4K HDR image. It’s compatible with every major HDR format. And it’s equipped with two full-bandwidth HDMI 2.1 inputs to support 4K 120 Hz gaming from the newest Xbox and PlayStation consoles. Add in the intuitive, fully featured Google TV smart-TV platform, and the U8H’s price-to-performance ratio is of inarguable value.

Chief among the U8H’s many strengths is its impressive peak brightness. When sending it HDR test patterns, I measured an average brightness of 1,500 nits, with peaks just north of 1,800 nits (a measurement of luminance; see TV features, defined for more info). To put that into perspective, consider that the 65-inch version of our budget 4K TV pick (the TCL 5-Series) typically costs around half as much as the 65-inch U8H but achieves only around 30% to 40% of its brightness. On the other side of the coin, the 65-inch version of our upgrade pick (the Samsung QN90B) costs almost twice as much as the 65-inch U8H, but it achieves only nominally higher brightness. Adequate light output creates convincing highlights and image contrast and (when necessary) combats ambient light from lamps or windows. It is a necessity for any TV worth buying—especially if you hope to watch HDR movies or play HDR games—and the U8H simply outpaces most TVs in its price range (and some in the next price bracket up, too).

Key to this functionality is the U8H’s employment of mini-LED backlighting with local dimming, which allows this TV to produce very bright light while still maintaining satisfyingly deep black levels that are typically free of blooming (or light bleed that’s visible around bright objects against a dark backdrop). This not only ensures impressive image contrast, it also makes the U8H a viable choice for most rooms, whether they’re brighter than average or dimmed down like a movie theater.

That’s not to say the U8H has pixel-precise light control—it’s not an OLED TV, after all—but it does a terrific job most of the time. In fact, in our tests, the U8H bested last year’s upgrade pick, the Samsung QN90A, in certain scenarios: The intro to Guillermo del Toro’s Cabinet of Curiosities on Netflix features the filmmaker against a pitch-black backdrop. Though last year’s QN90A failed to maintain perfect control over dimming elements during this scene (the black backdrop brightened distractingly once a sufficient amount of brighter content appeared on screen), the U8H did not. (For the record, the newer QN90B also passed this test.) The U8H’s mini-LEDs also help the screen look uniformly bright: Although the U8H is still not as good as an OLED TV in this respect, it shows very little indication of being a backlight-driven display, even during tricky scenes with large swaths of dim lighting.

The U8H’s brightness, black-level integrity, and local-dimming abilities make this an excellent TV for watching HDR content. The U8H is capable of playing HDR content in all of the major formats (HDR10, HDR10+, Dolby Vision, and HLG), but when it comes to impressive HDR, what’s under the hood is much more important than format compatibility. The most crucial thing for good HDR is high brightness and deep color saturation, and the U8H’s quantum dots achieve the latter. It’s not as simple as just having quantum dots, however: While many TVs (even the budget options) have quantum dots nowadays, what is often not taken into account is that brightness directly affects color saturation. For example, both the 2022 TCL 6-Series and the Hisense U8H are equipped with quantum dots, mini-LED backlights, and local dimming. But because the U8H is notably brighter than the 6-Series, it also achieves a higher total color volume. During our color-volume testing, the U8H exhibited color ranges at more than 100% of the DCI-P3 color space (the range of color needed to properly display HDR content), and it is capable of roughly 10% more total color volume compared with the 6-Series.

What does this mean in real-world terms? It means that the Hisense U8H truly excels as a modern 4K HDR TV, whether you’re watching the latest episode of Rings of Power or playing Overwatch 2. While watching HDR content side by side on the U8H and on our upgrade pick, the Samsung QN90B, I was truly surprised by how similar they looked at times, given that our upgrade pick is much more expensive. That said, though the U8H achieves impressive results where light output and color volume are concerned, it also exhibited some occasional video processing and upscaling issues (see Flaws but not dealbreakers), which videophiles and AV enthusiasts may take umbrage with. But in general, the picture quality punches well above its weight, metaphorically speaking.

And thanks to Hisense’s inclusion of Filmmaker Mode, it’s easy to rein in the U8H’s brightness abilities for a more-subdued and filmic experience in a darker room. Our measurements revealed that this mode has a very accurate white balance, mostly accurate colors (green is a bit oversaturated, but not egregiously so), and a perfect “dark room” gamma (which controls how quickly the video signal transitions from dark to light). Additionally, the TV’s 120 Hz refresh rate means it can play Blu-ray discs at 24 fps without the judder that’s usually present on TVs with 60 Hz refresh rates.

The TV’s higher refresh rate also reduces motion blur in faster-moving sports and allows for smoother, more stable motion in games. Two of the four HDMI inputs support 4K gaming at 120 Hz. The U8H measured low input lag while playing in 4K resolution, and Hisense’s helpful GameZone setting in the picture menu allowed me to confirm the presence of 120 Hz playback and variable refresh rate during games.

The onboard Google TV smart platform is another feather in this TV’s cap. As usual, however, it will be much more satisfying to use if you have a Google account and already take advantage of Google’s connected services, like Photos. The experience of navigating the TV’s smart features—scanning QR codes to sign into apps, using the onscreen keyboard, and browsing your Google Photos to set a photo as a screensaver—was very satisfying in terms of responsiveness and speed. Powering on the TV and booting into an app took just seconds. The included Bluetooth remote is also equipped with a handy “Hey Google” button, allowing you to pull up Google’s assistant and use voice commands to search for content or set a reminder. If you have multiple users with their own Google accounts, you can designate separate profiles (attached to a Gmail account) so that each user can customize the experience to their liking, as well as access their own Google Drive or Photos. While some reviewers have reported instances of momentary freezing while using the U8H’s platform, I didn’t personally experience any instances of slowdown that were egregiously worse than with any other smart-TV platform.

In terms of design, the Hisense U8H is not as svelte as our upgrade pick, but it’s plenty sturdy and doesn’t look or feel cheap. Two narrow, metal feet jut out from beneath the panel and steadily hold the TV. They can be attached in two separate spots, either closer in toward the middle of the panel or out toward the edges, to account for different-size TV stands. The feet are also equipped with cable organization clasps—a nice touch for keeping your TV stand free of cable clutter. Though the TV is primarily plastic, its bezels are lined with metal strips, providing a bit more durability in the long run. I moved it around my home, and it was no worse for wear, but we’ll know more after doing some long-term testing.

The Hisense U8H has some difficulties with banding, or areas of uneven gradation, where transitions that should appear smooth instead look like “bands” of color (sometimes also called posterization). Like many current 4K HDR TVs, the U8H uses an 8-bit panel rather than a 10-bit panel, which affects the color decoding and color presentation process. This is usually relevant only with HDR video and games. When playing games on the PlayStation 5 and Xbox Series X, I saw a few instances where the content wasn’t rendered correctly and displayed ugly splotches of color on the screen. However, this almost always occurred during static screens (such as a pause menu or loading screen); I rarely spotted it during actual gameplay. Hisense has stated that it would address the problem in a future firmware update, but at the time of writing it was still present. This is a flaw that may give dedicated gamers pause, but we don’t consider it to be a dealbreaker for most people.

I also saw occasional instances of banding with TV shows and movies, though they were few and far between. The U8H isn’t the best at upscaling sub-4K content, so videos with a 1080p or lower resolution looked a little soft. You can get better overall video processing and upscaling by springing for our upgrade pick (this is one reason it’s more expensive, after all).

Although the UH8 TV has four HDMI inputs, only two of them are fully HDMI 2.1–compatible. And one of those is designated as the eARC input (intended as an audio connection for a soundbar or AV receiver connection). So if you’re pairing an external audio system with the U8H, you may have only one input remaining that can support HDMI 2.1 features like 4K 120 Hz playback, variable refresh rate, and auto game mode; this could be a dealbreaker if you own more than one current-gen gaming console. If you’re in that boat, you may want to splash out some extra dough for our upgrade pick. Additionally, folks using pre-HDMI source devices—like the five-cable composite connector with green, red, blue, and red/white audio inputs—should be aware that this TV requires an adapter to allow those devices to connect, and an adapter is not included in the box.

Finally, like most TVs that use vertical alignment (VA) LCD panels, the U8H has a limited horizontal viewing angle, which may be a bit annoying if you’re hoping to entertain a large crowd. Our upgrade pick uses a special wide-angle technology to address this.

If you’re watching in a darker room and want the most accurate picture you can get—preserving the director’s intent—select the U8H’s Filmmaker Mode as your picture mode. In a brighter room, we recommend the Theater Day picture mode. In either case, you should go into the backlight settings, disable the automatic light sensor, and set the backlight to your personal preference. This is true whether you’re watching SDR or HDR content.

For gaming, use the game picture mode (the TV should switch into this mode automatically when paired with the newer game consoles), and then go into the Gaming submenu to make sure the right settings (VRR) are enabled. We recommend leaving the HDMI setting in “auto,” unless you notice that your game console is incorrectly identified.

The television is one of the most common electronic in any household. Even in the age of digital media, people choose to spend their free time at home with their families watching television.

Some people are hooked to watching show after show, putting their eyes at risk. But screen type is not the only factor in eye-healthy screen time. It really depends on the TV brightness, room lighting, distance from the screen, and view time. How? Let’s break it down:

Whatever type of television you have, it emits light with most TVs emitting at least 50% of blue light. Because blue light is closer to UV rays on the light spectrum, it may have similar qualities to how it affects people. Blue light exposure has long been linked to health issues such as eye damage, vision loss, and insomnia. So, as the brightness of your TV is increases, the color, and contrast of the image decrease, causing eye strain.

Ambient lighting should be present in the room when watching TV. It’s not a good idea to watch TV in complete darkness -- yes we’re talking to you late-night viewers. The room’s brightness should be adequate and comparable to the television. Even in theaters, the lights are never completely off, just dimmed; that same rule should apply to your home.

The closer you go to the television, the more your eyes begin to strain. For both kids and adults, it is not necessary nor healthy to sit close to the screen. The basic rule is to sit at least five times as far away from the screen as it is wide. So, if your television is 32 inches wide, for example, the ideal viewing distance is 160 inches or around 13 feet.

The recommended viewing distance for televisions with 4K resolution is one and a half times the screen size. The recommended distance for HDTVs is three times the screen size of the TV. These guidelines also go for children, who may be the biggest culprits in non-safe viewing practices. If you must, rearrange your living room to space out the good seats away from the TV.

How does that translate into TV screen types? And what screen type should people use to better protect their eyes when watching various shows on television?

The most common display technologies are LED and LCD. The latest TV display technology is OLED, which is only available on high-end TVs. The pixels used to provide the display are the difference between LCD, LED, and OLED. When compared to LED backlight, OLED has a far higher resolution and delivers cleaner, better graphics.

An OLED (Organic Light-Emitting Diodes) screen consists of numerous pixels that emit its own light. Each pixel is made up of three separate RBG – red, blue, and green – OLEDs. OLEDs are true emissive components that produce light on their own and do not require a light source. Meaning they produce a light that’s more natural and less harsh on your eyes.

OLED TVs also provide excellent color and contrast because they do not use light from other sources to display colors, as LCD/LED TVs do. They also, on average, produce around 20% less blue light than LCD displays.

Both LCD and LED TVs work in similar ways to each other. The only difference between the two is the type of backlighting. A TV labeled as an LED utilizes LED illumination for the white backlighting instead of fluorescent (CFL) lamps.

While LED LCD TVs are more appealing than CFL LCDs, they cannot compete with OLED panels since the LCD/LED front panel is a liquid color display that is not self-emissive. Which is the biggest disadvantage of LCD/LEDs in terms of eyesight. Although they produce quality images, the color and contrast from these displays are due to their light sources, so they give off more brightness that can cause eye strain if not moderated.

To sum it up, OLED displays are better for your eyesight. They have more natural lighting, better color contrast, and a wider color range. However, no matter what type of display you have, you will hurt your eyesight if you don’t practice safe TV viewing.

Plasma TVs contain tiny pockets of gas, and when a voltage is applied to them, they turn into a plasma state. The voltage then strikes the mercury within the plasma to emit ultraviolet (UV) rays, which pass through phosphor cells to produce an image. Each pixel in the TV contains three phosphor cells: red, green, and blue, and these three colors combine to produce a color. Essentially, plasma TVs don"t require a backlight, and each pixel is self-emissive as it produces its own light.

Unlike plasma TVs, LCD TVs use a backlight. Initially, LCD TVs used Cold-Cathode Fluorescent Lamp (CCFL) as their backlight. These are long tubes that are placed horizontally across the screen behind the LCD panel. When the light is turned on, it applies a voltage to the pixels, which makes them rotate a certain way to allow light through and produce an image. When it wants to display black, the pixels are rotated to create an opaque screen so that light doesn"t get through. This is what makes them different from plasma TVs because each pixel isn"t self-emitting.

Light-Emitting Diode (LED) TVs are the same as traditional LCD TVs, but instead of using CCFL backlights, they use many smaller LED lights. It produces an image the same way as a regular LCD TV because it still uses an LCD panel, but it has more control over the backlighting. The LEDs can be placed along the edges, which is called edge-lit LED, or all over the back panel, which is either called direct LED or full-array backlighting. You can see the differences between LCD and LED TVs below.

It"s also important to note LED is simply a marketing term used by manufacturers to describe their backlight. They"re still technically LCD TVs, but since calling them LED is so common now, we even label them as LED, and we"ll continue to do so throughout this article.

Plasma and LED TVs each present their own advantages and disadvantages in terms of picture quality, price, build, and availability. It"s generally thought that plasma produces a better picture quality due to their superior contrast ratio, but LED TVs became more popular because of other factors, like a lower cost and greater availability.

Below you can see the differences in picture quality between two older TVs from 2013. It"s clear the plasma was better at the time, but LED TVs have also gotten better since then, so picture quality has greatly improved.

Contrast ratio was one of the main advantages and selling points of plasma TVs. Since each pixel emitted its own light, it simply turned itself off when it wanted to display a black image. This allowed the TV to display very deep blacks, but because there was always a bit of charge left in the plasma, it still wasn"t a perfect black level.

On the other hand, LED TVs can"t achieve a perfect black level because the backlight is always on. However, technology has evolved to greatly improved the contrast of LED TVs, even to the point where it"s also as good as what plasma once was. There are two main types of LCD panels in TVs: Vertical Alignment (VA) and In-Plane Switching (IPS). VA panels produce a better contrast than IPS, and high-end TVs also have local dimming features that turn off certain zones of the LED backlights. Still, you won"t get a perfect black level, but most modern LED TVs produce such deep blacks that even in a dark environment it looks like perfect black levels. For reference, plasma TVs had a max contrast of about 4,000:1, according to DisplayMate.com, but some recent LED TVs can reach a contrast of over 20,000:1 with local dimming enabled, like the Samsung QN90A QLED.

LED TVs are a clear winner here, and it"s one of the reasons why they surpassed plasmas in terms of popularity. LED TVs get significantly brighter, so they can fight glare from light sources easier. Additionally, plasma TVs had to use glass on their front panel, which caused intense glare if you had any lamps or windows around the TV. LED TVs can use a coating on their glass panel to help reflect and diffuse light, making it a better choice for well-lit rooms.

Plasmas were designed for dark-room viewing, but since most people don"t have dedicated home theater setups and often watch with a few light sources around, they weren"t that useful. As you can see below, the plasma TV had pronounced reflections, to the point where it"s even hard to see the image, and instead you"re watching yourself watch TV. Reflections are still noticeable on an LED TV, but at least you can see the image.

Pixels on plasma TVs emitted light in all directions, creating extremely wide viewing angles, much better than most LED TVs. This means that the image remained accurate when viewing from the side, which was great for watching sports or a show with a few people. Out of the two main panel types for LED TVs, IPS has wider viewing angles than VA panels, but it"s still not as good as plasma.

TV manufacturers have tried different technologies to improve viewing angles on VA panels. Samsung has an "Ultra Viewing Angle" layer, and Sony uses their "X-Wide Angle" technology to increase the viewing angles, both at the cost of a lower contrast ratio. It"s still not as good as plasma, but they"re wide enough for watching TV in a fairly large seating area.

Below you can see the differences in viewing angles between a plasma and a VA panel. These TVs were tested on different test benches, so you shouldn"t directly compare the videos, but we included them to give you an idea of how each technology affects the viewing angle.

Plasma TVs were great for motion handling, like with sports and video games due to their quick response time. Since each pixel had to retain a certain charge at any given moment, it was ready to display an image almost instantly. This meant fast-moving scenes looked crisp and smooth, with no motion blur behind them. However, for LED TVs, it can be a toss-up; some lower-end models have a slow response time that causes motion blur, while other high-end TVs have a really fast response time.

Some LED TVs also use Pulse Width Modulation to dim their backlight, and this causes the backlight to flicker, which may create image duplication in fast-moving scenes. This can be particularly annoying, especially if you"re watching sports with fast-moving content.

In terms of refresh rate, plasma TVs had a higher internal refresh rate, up to 600Hz, while LED TVs tend to be 60 or 120Hz. However, the refresh rate depends on the content, and since most content doesn"t go past 120 frames per second, having a higher refresh rate TV isn"t very useful.

Screen uniformity is another area where plasma TVs win. Since they didn"t have a backlight, they could evenly control each pixel. LED TVs can suffer from uniformity issues, like darker edges or Dirty Screen Effect in the center, because the backlight output may not be even across the panel. However, this is only really noticeable when watching content with large areas of uniform color, like a hockey or basketball broadcast, or if you"re going to use the TV as a PC monitor. It shouldn"t be noticeable with other types of content, and since uniformity can vary between units, you shouldn"t worry about it too much.

One of the reasons plasma TVs didn"t last too long at the top of the TV world is because of their risk of temporary image retention and permanent burn-in. Plasmas lose their brightness over the years, and in the worst case, would have permanent burn-in with certain colors staying on the screen, as you can see here. Even after watching content with static elements, like the news, for an extended period, the outline of the static elements would stay on the screen for a few minutes after changing the channel.

These problems are particularly annoying, especially if you watch a lot of TV. There was no way to help reduce this issue, and after a few years, depending on how much you used the TV, your plasma would need replacing. LEDs don"t suffer from this same permanent burn-in, so you won"t have to worry about replacing your LED TV down the line because of burn-in.

Due to their different technologies, LED and plasma TVs are built differently. Plasma TVs tended to be heavier and thicker because the panel itself was larger. Although plasmas were the first flat-screen TVs available at a consumer level at the end of the 20th century, LCD TVs quickly became even thinner, easier to package, and lighter to carry from the store to your house. These days, LED TVs are as thin as 1", like the Samsung QN85A QLED.

Plasma TVs also required a lot of power to work and tended to get very hot. With the growth of environment-friendly consumer practices, it became clear LED TVs would win out since they required a lot less electricity, and in a way were better for the environment.

Both plasma and LED TVs were made with larger sizes, but LED had a slight advantage because they were also made in displays smaller than 32 inches, like with monitors. Although small TVs are rare now, you can still find a basic 28 or 32 inch TV for a kitchen or bedroom with an LED panel. Plasma TVs weren"t made that small. LED TVs also cost less to produce and are cheaper on the market, so at the end of the day, the lower cost drove LED sales.

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