lcd panel test images brands

With LED-backlit LCD TVs, gray uniformity issues are caused by a couple of factors. LCD panels are pretty sensitive to pressure, so extra pressure caused by misalignment of the TV"s components or by mishandling of the panel during manufacturing or shipping could lead to defects appearing. Also, too much pressure can affect the backlight and how much light it diffuses, which causes some areas to be darker. Size may also have an effect because it"s harder to keep a larger screen uniform, but since we only test one size of each TV, we can"t draw any conclusions about this.

Gray uniformity is unique to each individual panel. This means that no two TVs, even of the same model, will have matching uniformity. Generally, though, higher-end TVs should have better gray uniformity, as the manufacturers will have stricter standards for the panels used. Higher-end LED-backlit TVs tend to use either Mini LED or direct LED backlighting, generally better for uniformity than edge-lit TVs.

LED and OLED TVs use different technologies to display an image. While LED TVs are really LCD TVs backlit by LED backlights, OLEDs don"t have any backlighting and instead turn each pixel on and off. As such, they perform differently when it comes to uniformity. For the most part, OLEDs tend to have better uniformity, and there are rarely any issues. LED TVs can suffer more from uniformity issues, especially if their backlight is edge-lit and not direct LED. However, we can"t confidently say one TV will have better uniformity than another just because of the backlight or panel type.

Early OLEDs had issues when displaying 5% gray images. There would often be faint horizontal and vertical lines that you could notice in near-dark scenes. It"s rare to see that issue on modern OLEDs, but it"s still possible. Below you can see the LG B8 from 2018, which has very noticeable lines, and the LG B1 from 2021, which doesn"t.

We test gray uniformity on monitors the same way as on TVs. While you can"t compare the final scores, you can still compare the standard deviations and the pictures. Generally speaking, there isn"t a big difference in the total standard deviation with the 50% gray image on LED-backlit TVs and monitors, as they can each suffer from backlight bleed along the edges. The big difference here between monitors and TVs is the amount of dirty screen effect in the center. Monitors rarely have that issue, and only four monitors have worse DSE than the best TV we"ve tested.

Although it may seem like gray and black uniformity are the same, they test for different things. The gray uniformity test is meant to see how well the TV displays a single uniform color, but black uniformity is to see if there"s blooming around bright objects. You may see some issues that are the same in both, like vignetting, but the tests aren"t exactly related.

Unfortunately, gray uniformity is entirely down to the panel you get. There isn"t much you can do to improve gray uniformity as it"s down to panel lottery. You can try massaging the screen with a soft cloth to relieve the pressure, but this is a delicate technique, so it may be best to not do it if you"re unsure of yourself.

Unfortunately, there aren"t many steps that you can take to improve gray uniformity – it’s entirely down to the panel you get. You can try massaging the screen, but that"s hard to do. If you find yourself with uniformity that you can"t live with, you should exchange your TV for a different unit, or even a different model.

The large majority of monitors have LCD panels, which stands for liquid crystal display. A voltage is applied to the liquid crystals in each pixel, which rotate to allow the pixel to produce a color. This is a very basic way of explaining it, but if the same voltage is applied to the crystals for long periods, they may retain their same shape and continue producing the same image. The type of content displayed also impacts potential image retention. An operating system"s user interface, like the taskbar or windows, usually stay on the screen for long periods, and that could cause image retention when you close them. You can get away with a gaming monitor that has image retention if the game doesn"t have many static elements.

The type of panel used also affects image retention. With monitors, there are three common types of LED-backlit LCD panels: IPS, VA, and TN. Although image retention is something that can vary between units, IPS panels generally suffer from image retention more than the other two. However, this doesn"t mean that VA or TN panels are immune to image retention, and we"ve seen some VA panel monitors that show signs of it, like the Samsung Odyssey G9.

OLED panels are different from LCD panels because each pixel is individually-lit, as there"s no backlight. These panels tend to suffer from image retention. Many monitor manufacturers are reluctant to use OLED panels because they also have the risk of long-term permanent burn-in.

OLED panels are known for both image retention and permanent burn-in. Only a few monitors have OLED panels, and they"re more popular with TVs. Many OLED TVs that we"ve recently tested don"t show signs of image retention, but they"ll always face the risk of permanent burn-in. We don"t expect this to be an issue for people who watch varied content, but it could pose a problem if you watch a lot of content with static elements, like the news, or if you use your OLED TV as a PC monitor. LED TVs appear to be immune to long-term burn-in, which you can read about here.

Lowering brightness:Lowering the brightness can help reduce image retention, and in the long run, burn-in, on OLED panels. It shouldn"t really affect image retention on LEDs.

Screensavers:When you take a break from your screen, like when you get up for a coffee or to eat, use screensavers while the computer is idle. A slideshow would be ideal since the computer rotates between different images, and one image doesn"t stay on for a long period.

Temporary image retention happens when high-contrast elements stay on the screen for a long period and appear to stay on-screen for a few moments after they"re removed from the display. Although it"s rare, some monitors may show signs of image retention, but the images generally disappear after a few moments. There are a few ways to help reduce the risk of image retention, like lowering the monitor"s contrast or using screensavers. Temporary image retention is also different from long-term burn-in, so you shouldn"t have to worry that your monitor is broken if it shows some image retention.

Here we would like to show you a simple method to check LCD display quality. You can get a good idea of whether the basic display quality is good or bad just by looking at how some simple test images are displayed, just like in the introductory quiz. First of all, we would like you to get a sense of how important it is that "image data can be properly displayed" by checking the display of the LCD that you currently use, (that"s right, the one you are using to view this page!).

The test items use colour / monochrome patterned images to check gradation expression, and simple images to check brightness / chromaticity variation. Downloads are available of several test images, such as gradation patterns. We would like you to display the downloaded test images in photo retouching software or a viewer that can reproduce colour accurately. As we mentioned at the start of this article, you have to be careful as in many cases colours cannot be displayed accurately in web browsers. (Currently only a few browsers such as Safari and Firefox 3.x can handle colour management).

Before starting your visual check of the display quality, please return to your LCD"s setting to default, and select Adobe RGB or sRGB as the image quality mode. If these modes are not available it is fine to set the colour temperature to 6500K and gamma to 2.2. If you cannot adjust the colour temperature and gamma, simply adjust the brightness and contrast so that they are easier to discern. Of course, if it"s an LCD environment that has been colour calibrated it"s OK to leave it as it is.

The average LCD takes some time for the monitor to stabilize after it is switched on so, after start up, please wait at least 30 minutes or so before doing the test. (Most EIZO monitors are an exception to this as they are equipped with our proprietary dimming function and the monitor stabilizes in a short time after start up.)

In the past decade, LCD monitors have replaced CRT screens for all but the most specialist applications. Although liquid crystal displays boast perfect

If you already know how to use these images.For viewing the images off-line (120 kB ZIP).All images, but with the color profiles stripped, in case you

© Copyright Han-Kwang Nienhuys, 2008. The text and accompanying images may not be redistributed. This includes placing the images on other websites, either as a copy or through hotlinking. Read more...

LCD (liquid crystal display) is the most widely used display technology. They are used for automotive, appliance, telecommunication, home appliance, industrial, consumer electronic, military etc. But LCD displays have some drawbacks, such as slow response, narrow viewing angle, lower contrast etc. One annoying phenomenon often complained about by users is image sticking.

If a fixed image remains on a display for a long period of time, the faint outline of that image will persist on the screen for some time before it finally disappears. Normally, it happens to LCD and plasma screens, but for the purpose of our discussion, we will focus on TFT LCD displays. Image sticking is also referred to as “image persistence”, “image retention”, “ghosting” or “burn-in image.”

An LCD screen includes a thin layer of liquid crystal material sandwiched between two electrodes on glass substrates, with two polarizers on each side. A polarizer is an optical filter that lets light waves of a specific polarization pass through while blocking light waves of other polarizations. The electrodes need to be transparent so the most popular material is ITO (indium tin oxide). Since an LCD can’t emit light itself, normally a backlight is placed behind an LCD screen in order to be seen in a dark environment. The light sources used for a backlight can be LED (light emitting diode) or CCFL (cold cathode fluorescent lamps). The LED backlight is the most popular. Of course, if you want a color display, a layer of RGB color filter can be made into an LCD cell. A touch panel can also be added in front of an LCD display.

When an electric field is applied to the liquid crystal molecules, they become untwisted. When the polarized light reaches the layer of liquid crystal molecules, the light passes straight through without being twisted. When it reaches the second polarizer, it will also pass through, meaning the viewer sees the display as bright. Because LCD technology uses electric fields instead of electric current (electron passes through), it has low power consumption.

The cause of LCD image sticking is due to an accumulation of ionic impurities inside the liquid crystal materials. When slight DC voltage occurs, the charged impurities will move the electrodes and build up a reversed voltage field. When the power is removed, the reversed voltage will kick in to make the LCD molecules twisted different from the other part of the LCD, which shows up as the image sticking. The longer the time, the more impurities will migrate, the larger the reversed voltage will be, and the imaging sticking will appear worse.

For LCD manufacturers, try to protect liquid crystal materials exposed to the air by using nitrogen gas or dried air to avoid absorbing moisture that can create a huge amount of impurities in the liquid crystal material, as water is an excellent solvent. Controlling the humidity of the fab is also very important, as is selecting the right liquid crystal materials and their manufacturers. Different liquid crystal materials have different moisture absorbing abilities. Different liquid crystal material factories have different capabilities in terms of controlling impurities. Despite the fact that high purity can mean high in cost, using higher purity liquid crystal materials and designing the circuitry to get rid of DC in LCD display drivers can avoid an image sticking issue.

Unlike the “burn-in” issue common with CRTs, an image sticking issue is not permanent. It will eventually recover after some time. One way to expedite erasing a retained image is to have a screen on in an all-black pattern for 4-6 hours. If you want to make it even faster, the display can be put into an environment with a temperature of around 35 to 50°C for 1-2 hours. As this elevated temperature is within the working temperature range, it will not damage the LCD panels.

There are plenty of new and confusing terms facing TV shoppers today, but when it comes down to the screen technology itself, there are only two: Nearly every TV sold today is either LCD or OLED.

The biggest between the two is in how they work. With OLED, each pixel provides its own illumination so there"s no separate backlight. With an LCD TV, all of the pixels are illuminated by an LED backlight. That difference leads to all kinds of picture quality effects, some of which favor LCD, but most of which benefit OLED.

LCDs are made by a number of companies across Asia. All current OLED TVs are built by LG Display, though companies like Sony and Vizio buy OLED panels from LG and then use their own electronics and aesthetic design.

So which one is better? Read on for their strengths and weaknesses. In general we"ll be comparing OLED to the best (read: most expensive) LCD has to offer, mainly because there"s no such thing as a cheap OLED TV (yet).

Take this category with a grain of salt. Both TV types are very bright and can look good in even a sunny room, let alone more moderate indoor lighting situations or the dark rooms that make TV images look their best. When it comes down to it, no modern TV could ever be considered "dim."

The better LCDs have local dimming, where parts of the screen can dim independently of others. This isn"t quite as good as per-pixel control because the black areas still aren"t absolutely black, but it"s better than nothing. The best LCDs have full-array local dimming, which provides even finer control over the contrast of what"s onscreen -- but even they can suffer from "blooming," where a bright area spoils the black of an adjacent dark area.

Here"s where it comes together. Contrast ratio is the difference between the brightest and the darkest a TV can be. OLED is the winner here because it can get extremely bright, plus it can produce absolute black with no blooming. It has the best contrast ratio of any modern display.

One of the main downsides of LCD TVs is a change in picture quality if you sit away from dead center (as in, off to the sides). How much this matters to you certainly depends on your seating arrangement, but also on how much you love your loved ones.

A few LCDs use in-plane switching (IPS) panels, which have better off-axis picture quality than other kinds of LCDs, but don"t look as good as other LCDs straight on (primarily due to a lower contrast ratio).

OLED doesn"t have the off-axis issue LCDs have; its image looks basically the same, even from extreme angles. So if you have a wide seating area, OLED is the better option.

Nearly all current TVs are HDR compatible, but that"s not the entire story. Just because a TV claims HDR compatibility doesn"t mean it can accurately display HDR content. All OLED TVs have the dynamic range to take advantage of HDR, but lower-priced LCDs, especially those without local-dimming backlights, do not. So if you want to see HDR content it all its dynamic, vibrant beauty, go for OLED or an LCD with local dimming.

In our tests comparing the best new OLED and LCD TVs with HDR games and movies, OLED usually looks better. Its superior contrast and lack of blooming win the day despite LCD"s brightness advantage. In other words LCD TVs can get brighter, especially in full-screen bright scenes and HDR highlights, but none of them can control that illumination as precisely as an OLED TV.

The energy consumption of LCD varies depending on the backlight setting. The lower the backlight, the lower the power consumption. A basic LED LCD with its backlight set low will draw less power than OLED.

LG has said their OLED TVs have a lifespan of 100,000 hours to half brightness, a figure that"s similar to LED LCDs. Generally speaking, all modern TVs are quite reliable.

Does that mean your new LCD or OLED will last for several decades like your parent"s last CRT (like the one pictured). Probably not, but then, why would you want it to? A 42-inch flat panel cost $14,000 in the late 90"s, and now a 65-inch TV with more than 16x the resolution and a million times better contrast ratio costs $1,400. Which is to say, by the time you"ll want/need to replace it, there will be something even better than what"s available now, for less money.

OLED TVs are available in sizes from 48 to 88 inches, but LCD TVs come in smaller and larger sizes than that -- with many more choices in between -- so LCD wins. At the high end of the size scale, however, the biggest "TVs" don"t use either technology.

You can get 4K resolution, 50-inch LCDs for around $400 -- or half that on sale. It"s going to be a long time before OLEDs are that price, but they have come down considerably.

LCD dominates the market because it"s cheap to manufacture and delivers good enough picture quality for just about everybody. But according to reviews at CNET and elsewhere, OLED wins for overall picture quality, largely due to the incredible contrast ratio. The price difference isn"t as severe as it used to be, and in the mid- to high-end of the market, there are lots of options.

With phosphor-based electronic displays (for example CRT-type computer monitors, oscilloscope screens or plasma displays), non-uniform use of specific areas, such as prolonged display of non-moving images (text or graphics), repetitive contents in gaming graphics, or certain broadcasts with tickers and flags, can create a permanent ghost-like image of these objects or otherwise degrade image quality. This is because the phosphor compounds which emit light to produce images lose their luminance with use. This wear results in uneven light output over time, and in severe cases can create a ghost image of previous content. Even if ghost images are not recognizable, the effects of screen burn are an immediate and continual degradation of image quality.

Screen burn on an amber CRT computer monitor. Note that there are two separate burned-in images: one of a spreadsheet program, and another of an ASCII-art welcome screen.

Phosphor burn-in is particularly prevalent with monochromatic CRT screens, such as the amber or green monochrome monitors common on older computer systems and dumb terminal stations. This is partly because those screens displayed mostly non-moving images, and at one intensity: fully on. Yellow screens are more susceptible than either green or white screens because the yellow phosphor is less efficient and thus requires a higher beam current. Color screens, by contrast, use three separate phosphors (red, green, and blue), mixed in varying intensities to achieve specific colors, and in typical usage patterns such as "traditional" TV viewing (non-gaming, non-converged TV usage, non-Internet browsing, broadcasts without tickers or flags, no prolonged or permanent letterboxing) are used for operations where colors and on-screen object placement approach uniformity.

A nearly two-year-old LCD television showing extreme burn-in of CNN"s circa 2008 digital on-screen graphic; this television is in a McDonald"s restaurant where CNN is permanently turned on and displayed throughout the business day.

In the case of LCDs, the physics of burn-in are different than plasma and OLED, which develop burn-in from luminance degradation of the light-emitting pixels. For LCDs, burn-in develops in some cases because pixels permanently lose their ability to return to their relaxed state after a continued static use profile. In most typical usage profiles, this image persistence in LCD is only transient.

Both plasma-type and LCD-type displays exhibit a similar phenomenon called transient image persistence, which is similar to screen burn but is not permanent. In the case of plasma-type displays, transient image persistence is caused by charge build-up in the pixel cells (not cumulative luminance degradation as with burn-in), which can be seen sometimes when a bright image that was set against a dark background is replaced by a dark background only; this image retention is usually released once a typical-brightness image is displayed and does not inhibit the display"s typical viewing image quality.

Other examples: Apple"s iPhone X and Samsung"s Galaxy series both mitigate or delay the onset of burn-in by shifting the pixels every minute or so for the battery, Wi-Fi, location, and service bars. Also, parallax scrolling may be enabled for the home screen to give icons a 3D-like effect, a setting Apple refers to as "perspective zoom". AG Neovo patented Anti-burn-in technology is also using pixel shifting to activate the pixels to move by the designed time interval to prevent burn in effect on LCD monitors.

The most prevalent burn-in image on early televisions was said to be that of the RCA Indian-head test pattern, which would often follow the formal television station sign-off. This was due to the viewer leaving the television set on at the end of the day, which was not recommended by the television manufacturers.

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).

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.

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.

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.

Still, DSE may afflict cheaper versions, particularly if the anti-reflective coating on the glass that overlays the screen is of low quality or poorly applied. Furthermore, as the display ages, the phosphors in the screen may begin to wear out or malfunction, all of which can contribute to less uniform images, which is often apparent particular in scenes with fast panning shots.

In LCD and LED TVs, DSE is typically a bigger issue, one that"s due to the way these units are illuminated. Before we proceed, it"s worth mentioning that although marketing-speak often treats LED and LCD TVs as completely different technologies, they"re not different beasts.

LED units could be more accurately described as "LED-backlit LCD televisions," but salespeople and consumers alike are too lazy to utter that tongue-wearying phrase while haggling in a big-box store. What"s important to realize is that both categories rely on LCDs (liquid crystal displays), which act as shutters that either block light or allow it to pass, depending on the image that"s being rendered on the screen.

There are a variety of factors that affect LCD quality, notably illumination source. Older LCD TVs, for example, used multiple cold cathode fluorescent lamps (CCFL) to light LCDs from the rear. They provide generally smooth and even illumination, but they make the final product rather bulky.

If you"ve ever pressed a little too hard on your smartphone or computer screen, you"ve likely witnessed a bit of discoloration, clear evidence of how sensitive LCDs are to physical pressure. Now, picture a huge manufacturing facility that cranks out thousands of these units per week. It"s easy to see how a bit of mishandling could alter the screen"s consistency.

The same goes for shipping. Some units travel long distances in cargo boxes, and then take bouncy rides in your car to their final resting place on your living room wall. That"s a lot of opportunities for tiny mishaps to affect LCD uniformity.

Image quality assurance has traditionally been a high priority in medical imaging departments. Recently, it has often been neglected with the transition from hard copy (film) to soft copy (computer) display systems, which could potentially result in difficulty in reading images or even misdiagnosis. This transition therefore requires careful management such that comparable image quality is achieved at a minimum. It is particularly difficult to maintain appropriate image quality in the clinical settings outside of medical imaging departments because of the volume of display systems and the financial restraints that prohibit the widespread use of dedicated computers and high-quality monitors. In this study, a protocol to test and calibrate display systems was developed and validated by using an inexpensive calibration tool. Using this protocol, monitors were identified in a hospital in which image quality was found to be inadequate for medical image viewing. It was also found that most monitors could achieve a substantial increase in image quality after calibration. For example, the 0 and 5% luminance difference was discernable on 30% of the piloted display systems before calibration, but it was discernable on 100% post calibration. In addition, about 50% of the piloted display systems did not have the maximum luminance (white level) suitably set, and 35% of them did not have the minimum luminance (dark level) suitably set. The results indicate that medical display systems must be carefully selected and strictly monitored, maintained, and calibrated to ensure adequate image quality.

Although the quality of medical images (digital or otherwise) is strictly controlled during acquisition, it is often poorly maintained for soft-copy image review. Image quality control of softcopy display systems is often neglected because it can be an expensive and complex process to ensure. Most health institutions cannot afford to standardize on high-end medical display systems, but instead have a mix of various types

Display systems should be cleaned regularly with monitor cleaner to remove fingerprints and other stains. There are many different types of commercial monitor cleaners, including sprays (to be sprayed on a soft cloth before application), individual wipes, and boxed wipes. Cleaning solutions can vary from being polymer-based to a solution of 50% water and 50% isopropyl. Care should be taken not to use alcohol-based or ammonia-based cleaners because it could permanently damage the screen surface (e.g., turning LCD screens yellow and brittle, or damaging CRT monitor antiglare coatings).

The minimum luminance (dark level) must first be properly set by changing the “brightness setting.” Ideally, monochrome CRT monitors can be set between 0.2 and 0.5 cd/m2. Monochrome LCD monitors can usually be set at about 1.0 cd/m2. The lower the dark level the better, but at the same time, the monitor must be able to provide a maximum luminance adequate for the particular application (e.g., 170 cd/m2 for most images displayed on color monitors, and 350 cd/m2 for most images displayed on monochrome monitors).

The final step is a visual check. There are several geometric patterns and patterns of varying luminosity that can be helpful. One that is often used is the Society of Motion Picture and Television Engineers (SMPTE) pattern (see Fig 2). This pattern can be used to detect areas that are unfocused (horizontal and vertical thin lines that should be discernable) and to determine the proper contrast (especially the 0 to 5% luminance difference and the 95 to 100% luminance difference). The SMPTE pattern can also be used to align the window vertically and horizontally and to determine if there is skewing or bowing (pincushion effect). Other parameters to check include ghosting (i.e., when previous images linger), burn-in on CRT monitors, pixel dropout in LCD monitors, and nonuniformity of luminance (see Fig 3). Uniformity of luminance can be measured by placing the photometer on different quadrants of the monitor. Luminance nonuniformity is usually not a problem with LCD monitors, but can be a problem with CRT monitors. This can occur if the CRT phosphor coating is not applied evenly, if the phosphor on the edges of the screen gets less light than in the middle of screen due to the distorted electron beam, or if there is a misalignment in the CRT components. Nonuniformity is also prevalent in CRT monitors that are within a magnetic field.

Sixteen PACS workstations (11 dual-monitor systems and 5 single-monitor systems) were calibrated during the study. Three of the workstations were intentionally included for the pilot due to complaints of poor image quality, whereas the other workstations were randomly chosen out of approximately 1,000 workstations that are used for viewing medical images. They were selected from radiology reading rooms and clinics to represent a range of monitor types.

Four monitors out of the 27 monitors tested were found to be inadequate for medical image review even after calibration. The monitors were inadequate because either the maximum luminance for these monitors were about 90 cd/m2, which was much lower than the ideal maximum luminance of 170 cd/m2 for color monitors, or the monitors were visibly unfocused. In addition, the calibration photometer was not able to connect to two workstations, which had computers that were nonstandard to the hospital and were not supported by the hospital IT department. Both of the workstations had monitor quality deemed inadequate for image review and have been excluded from the following results summary.

Initial calibration and periodic testing of PACS monitors are important for maintenance of image quality. A degradation of image quality over a long time is often difficult for clinicians to detect. This can result in a delay in reporting of problems until the viewing of the images is severely degraded by the display.

The frequency of calibration and testing can vary greatly. Hospitals have performed weekly, quarterly, or even daily monitor tests, whereas others do not calibrate monitors at all.

Adding to the complexity of ensuring adequate image quality is choosing the proper supporting hardware (monitors, computers, and graphics cards). Although standardizing on a single vendor of PACS hardware can assist in the maintenance of the equipment, it is often difficult to achieve in practice because of financial constraints and/or the need to select different monitors for different applications. Space requirements might dictate theuse of an LCD monitor instead of the larger CRT monitor. The once prohibitively high cost of high-bright grayscale LCD monitors is becoming less of a problem as the cost of LCD monitors continually drop, whereas concurrently, the advancements in LCD technology lead to increasingly better image quality.

CRT and LCD monitors have their own strengths and weaknesses, but more institutions are moving from using CRT monitors to LCD monitors. Table 1 summarizes their characteristics.

The type of images that will be viewed on the PACS workstation will also influence the monitor selection and computer configuration. Here are some questions that need to be asked when developing a display system.Are the images monochrome or in color? The trade-off of color monitors is that they cannot achieve the level of luminance of grayscale monitors.

Are the images high-resolution and high-contrast (e.g., computed radiography) or low-resolution and low-contrast (e.g., magnetic resonance imaging) images? This will determine the required monitor resolution and the suitability of using grayscale monitors.

What is the volume of images that will be viewed on the PACS workstation? Are the images stacked (e.g., stacked computed tomography images). This will determine the computer requirements, such as processor speed, random access memory (RAM), and hard drive space.

Is the display system going to be used for primary diagnosis or for a clinical review? Are the structures that need to be identified gross structures (e.g., metal leads that were inserted into the body) or small, hard to discern structures (e.g., in mammography images)? This will influence several decisions regarding hardware selection, including the required bit depth of the graphics card. Most graphics cards are 8-bit digital to analog converters (DAC) allowing 256 levels of intensity for each red, green, and blue channel, but often higher-bit depth cards are preferable (10-bit cards) for monochrome monitors.

Will past and current images of the same patient need to be compared side by side? Will multiple views of the anatomy need to be viewed simultaneously? If so, then dual monitors will likely be required. In this case, care must be taken in choosing a graphics card that has two LUTs so that both monitors can be calibrated to the DICOM GSDF. Most graphics cards, especially the less expensive ones, do not have dual LUTs, which means that only one monitor can be calibrated.

Several medical display manufacturers are starting to develop methods to help achieve and maintain stable image quality. Many high-end monitors are now strictly factory-calibrated for medical viewing. There are also LCD monitors available that do periodic self-calibration with an internal backlight sensor or with a permanent photometer on the corner of the monitor. Unfortunately, these are usually very expensive high-end monitors.

The proliferation of PACS has permitted the softcopy review of medical images outside, as well as within, the radiology department. Although the selection of proper display system hardware will vary depending on the application and the environment, maintaining proper image quality should always be a consideration for the system"s ongoing use. This is often a difficult program to establish and maintain due to limited human and financial resources, the large number of display systems that are often nondedicated standard desktop computers and monitors, and the lack of comprehensive standards.

7. Wang J, Peng Q. An interactive method of assessing the characteristics of softcopy display using observer performance tests. J Digit Imaging.2002;15(Suppl 1):216–218. doi: 10.1007/s10278-002-5003-3. [PubMed] [CrossRef]

10. Gray JE, Lisk KG, Haddick DH, Harshbarger JH, Oosterhof A, Schwenker R. Test pattern for video displays and hard-copy cameras. Radiology.1985;154:519–527. [PubMed]

Expressly designed and tested for security and surveillance environments, AG Neovo’s patented Anti-Burn-in™ technology tackles the LCD monitor burn-in effect, otherwise known as a ghost image on the screen. Burn-in images result in the polarisation of the liquid crystal material contained within the TFT LCD panel. The Anti-Burn-in technology prolongs the lifetime of all AG Neovo monitors and displays featuring this technology to secure users’ investment.

LCD Burn-In, known as image sticking, image retention, image persistence, or ghost images, is the phenomenon where fixed images displayed on the monitor screen for extended periods cause the polarisation of the liquid crystal material contained within the LCD panel, making the image to be “burnt” on screen.

Burn-in on an LCD screen occurs because pixels permanently cannot return to their relaxed state after a static image is displayed on the screen over a long period of time. When a screen keeps displaying a single image, the crystals at those pixels will get a permanent memory, and thus the image on the screen will be imprinted onto them permanently. Once it causes screen burn-in, there is no recovery in most cases. Because of this, choosing a display or monitor allowing for pixel shift, like AG Neovo’s monitors with Anti-Burn-in, can help prevent LCD computer monitor burn-in.

“Image retention” and “Burn-in” are sometimes used interchangeably, but they are not precisely the same thing. Image retention, in most cases, is temporary and fixable. It appears when an image is temporarily “stuck” on the screen even if the content changes, but reversible by taking particular measures. Burn-in on the LCD screen is a form of image retention but is permanent and virtually impossible to fix. The prolonged use of static images would cause screen burn-in.

AG Neovo’s patented Anti-Burn-in™ technology tackles the LCD monitor burn-in effect, otherwise known as a ghost image on the screen. Burn-in images result in the polarization of the liquid crystal material contained within the TFT LCD panel. This technology prolongs the life of all AG Neovo monitors and displays to secure the user’s investment.

Anti-Burn-in technology is to activate the pixels to move by the designed time interval and protect panels from being seen the vaguely visible “residual image” under the static charge conditions so as to help prolong the lifetime of TFT LCD panels.

Unlike conventional displays, AG Neovo’s security and surveillance displays are built-in with Anti-Burn-in function to reduce the possibility of LCD burn-in for continuous security monitoring applications. It is not needed to create any screen saver, playback youtube video, or install additional tools to prevent burn-in effect.

Compared to the traditional LCD screen burn-in reduction tools which may cause evident interruption to the displayed images, AG Neovo’s patented Anti-Burn-in function is almost unnoticeable when applied. The specially designed three modes of Anti-Burn-in selection provide users with flexibility in choosing the optimal approach that best fits with their non-stop security monitoring.

Video surveillance is commonly used for monitoring of selected images to determine if an improper activity is occurring, such as theft, vandalism, and abnormal situations in daily operation, and any intervention is not allowed during the process. To ensure there are not any interruptions to the video monitoring, turning on a screen saver, reducing contrast/brightness or playing white static image for a particular while is not an option. Instead, selecting a security monitor with built-in Anti-Burn-in function is an efficient solution.

Burn-in on the screen is technically hard to fix. Instead, here are some tips on how to remove image persistence on LCD screens and prevent permanent effects:

Reduce screen contrast and brightness. Lower contrast allows even lighting levels across the LCD screen and thus has less strain on a specific area of the screen. Then, try to watch some different contents, and the effect of Image retention might go away on its own.

Turn on white static image for approximately as long as the persistent image was displayed; this is to use a completely white screen to overwrite the burn-in image. Or, create a screen saver that alternates between black and white images. The continuous changing of white/black across your screen can help alleviate the ghost image from the screen. The solid colour background might reset the image burn but is more likely to deal with image retention than image burn-in.