lcd panel test images factory

Have you ever properly checked the display quality of the LCD you habitually use? Very often people become aware of previously unnoticed problems in display quality when they run a check using test patterns and so on. This time we are going to talk about the basic points used to assess LCD display quality, and show you a simple way to test it.

Below is the translation from the Japanese of the ITmedia article "The difference in image quality is perfectly obvious! – Let"s check the LCD"s monitor" published April 22, 2010. Copyright 2011 ITmedia Inc. All Rights Reserved.

First of all, bear with us in the following simple test. Below is image data of a row of three squares. In the center of each square is a letter so faint as to be barely distinguishable, so there are three letters in all. Read from the left they make up a word. Can you see that hidden word?

That"s right. The answer is "LCD" (it is displayed if you drag the space between the brackets). We assume that probably many users could read the letters concealed in the squares.

So, the next test is much more difficult. A word is concealed in the four squares below, just as in the image above. The letters are written in colors that are very similar to those of the boxes and we expect that, in many cases, it is hard to distinguish them in your browser. We would like you to download the image and check it closely in photo retouching software or a viewer that is capable of accurate color reproduction.

This time the answer is "EIZO" (it is displayed if you drag the space between the brackets). Depending on the lighting or the user"s environment it may be hard to make out but, if you can read these four letters, the display quality, or more accurately the still image gradation expression, of your LCD is extremely high.

Let"s get down to details then. "Image quality" is the top priority of the LCD, of course. However, recently LCD prices are fiercely competitive and there are surprisingly few products that insist on high image quality and performance. It may be nice to be able to get hold of a wide-screen monitor with full HD (1920 × 1080 dot) resolution or higher fairly cheaply, but it cannot be denied that such LCDs tend not to place too much importance on display quality.

On the other hand, the increasing opportunities to enjoy things like HD videos and games, and high resolution digital photographs on the computer make LCD display quality even more important. As far as possible it"s best to use an LCD with excellent display quality in order to fully enjoy the charms of the visual content.

Even so, perhaps you think that there can"t really be that much wrong with the LCDs that so many people are using at the moment. 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 color / 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 color accurately. As we mentioned at the start of this article, you have to be careful as in many cases colors cannot be displayed accurately in web browsers. (Currently only a few browsers such as Safari and Firefox 3.x can handle color 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 color temperature to 6500K and gamma to 2.2. If you cannot adjust the color 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 color 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.)

The surface treatment of an LCD makes a difference to the background reflection. Glare panels impede the surface diffusion of backlight, which does make it easier to achieve high color purity, but also makes distinct reflections of the user or lighting much more likely (photo on the left).

If the lights are similarly trained on a non-glare panel they do not have much effect on the display, only appearing as a fuzzy brightness (photo on the right).

For your reference, we ran a test on an EIZO 24.1-inch wide-screen LCD, the FlexScan SX2462W, for this article. The FlexScan SX series comes with a number of high image quality functions and boasts top class display quality as a general-purpose LCD intended for a computer.

When we displayed the quiz images (the more difficult ones, of course) on the FlexScan SX2462W, the four letters appeared faintly when we stared closely at the screen and we could read what they said. This indicates the high image quality level.

When checking the display quality of an LCD it is comparatively easy to understand the gradation expression capability by a visual check. Let"s display color and monochrome gradation images and check whether the entire image is smoothly reproduced. If there is a problem with the gradation expression it produces things like blocked-up shadows in dark areas and blown-out highlights in light areas, banding (vertical or horizontal stripes) in the middle gradations, and color cast, so you should check for problems like these.

Test images of color / monochrome gradations are shown below. Each test image is prepared for three resolution levels (1280 × 800 dots / 1680 × 1050 dots / 1920 × 1200 dots). When you click on an image it is displayed in that actual resolution. We would like you to download the images in the resolution which matches that of your current LCD. Gradation expression can vary according to whether the image is viewed horizontally or vertically, so it will be more effective if you rotate these images and view them vertically as well.

A gradation pattern where the colors red, green, blue, cyan, magenta and yellow go through 16 gradients as they change to white or black. This is an easy test image so we expect that it can be seen in most environments that each color bar is divided into 16 blocks.

A gradation pattern where the colors red, green, blue, cyan, magenta and yellow go through 64 gradients as they change to white or black. Each color bar is divided into 64 rectangular blocks. With this many gradients we expect that many LCDs will find it hard to make distinctions in the dark areas or the areas that are close to primary colors.

A smooth gradation pattern where the colors red, green, blue, cyan, magenta and yellow go through 256 gradients as they change to white or black. At this level of difficulty you cannot distinguish between adjoining colors from a distance but, if you have an LCD with excellent gradation expression, if you look closely you should be able to see that each color is divided into thin rectangular blocks.

A gradation pattern that changes from black to white. It is divided into 5 horizontal bars: from the top, smooth, 128 gradients, 64 gradients, 32 gradients and 16 gradients. Even if all the differences can be distinguished in the 16 and 32 gradient patterns near the bottom, we expect that there will be some parts in the 64 and 128 gradient patterns where it is hard to see the boundaries between adjoining colors. With this kind of monochrome test image you should also check whether any unnecessary colors are mixed with the gray.

On an average LCD gradations of gray that are close to black tend to appear as blocked-up shadows (gradations of gray that are close to white are displayed comparatively accurately). If your LCD"s OSD menu allows you to adjust the contrast, please try gradually turning down the contrast. Turning down the contrast often makes it possible to see gradations that had been subject to blocked-up shadows or blown-out highlights.

Probably most LCDs will be able to detect some degree of banding and color cast in the middle gradations. Banding in the middle gradations is tone jump (Missing gradations) and, along with color cast, means that the RGB gamma curves are unequal. Unlike blocked-up shadows or blown-out highlights, this is an area that it is hard to improve with adjustments made by the user.

When we looked at these test images on the FlexScan SX2462W, in the smooth gradation there was blocked-up shadows right next to the black but we could distinguish differences in gradations of gray until very close to the black area. When it comes to such subtle gradation distinctions the brightness of the room and the adaptability of the eye come into play, so the range that is visible will vary according to the environment and the individual. The gradation expression was excellent, with almost no blown-out highlights in light areas, middle gradation banding or color cast.

A row of images of slightly different grays (1050 × 300 dots). If you cannot see the boundaries between the grays there is probably a problem with the display environment or gradation expression of your monitor.

The answer is "The far right" (it is displayed if you drag the space between the brackets). If the other grays looked correct, color may not be being correctly recognized for a variety of reasons, such as the lighting environment or the LCD settings.

Now let"s assess the gradation expression with some slightly different test images. Below are color patterns with a spread of pale colors in gradations close to the dark range and the light range. They are arranged so that a distinction cannot be made between adjoining colors on an LCD with insufficient gradation expression.

We expect that you could roughly get the whole picture in the gradation patterns on the previous page, but in the patterns this time some parts that cannot be seen may have appeared in some cases. As we mentioned earlier, LCDs tend to display gradations close to black as a blocked-up shadows, and color patterns that are close to black are particularly hard to distinguish.

Since there are some parts that cannot be seen, the possibility arises subtle skin colors and tones cannot be accurately recognized when doing things like retouching photographs, though the misrecognition will vary according to the user"s eyesight. People who place importance on color reproduction should probably bear this in mind when they think about replacing their LCD or buying an extra one.

Incidentally, when we checked the FlexScan SX2462W with these tests we could distinguish everything in both the close to white and the close to black patterns. As well as no blown-out highlights or blocked-up shadows, we saw no unnatural color casts.

Every LCD has some degree of brightness and chromaticity variation, but there are many products where the variations become more obvious when the brightness is lowered. A comparison of the brightness and chromaticity variation of a number of LCDs reveals that there is a fairly large difference between products, so this is a point to bear in mind.

If you actually try this test you may be surprised to find more variation than you expected when gray or a near-white pale color is displayed. Generally speaking, the center of an LCD screen is the brightest and it gradually gets darker towards the edges. This is no problem if there is not a big difference in brightness between the central and peripheral areas, but there are some products where this difference is very striking.

Incidentally, this test is also an effective way to test the LCD for dot defects (normal lighting / unlit room). We would like you to check the black display in a darkened environment, for example by switching off all the room lights at night. Although you probably saw the whole screen as uniformly black in a light environment, very often in a dark environment you can find variations in some parts due to light leaks.

The FlexScan SX2462W got good results again when we tried it with the brightness and chromaticity variation tests. The brightness decreased slightly at the edges of the screen, particularly the lower edge, but overall the display was even and pleasing. It is installed with a "digital uniformity equalizer" that measures brightness and chromaticity throughout the screen and makes corrections so that the entire screen is uniform.

Monochrome full-screen displays on a FlexScan SX2462W. Only the screen display is shown. The bottom right is a near-white pale orange. There are not many LCDs that can display this kind of pale color as uniformly as this

However, the pitfall here is that it simply means that "the screen is visible". The thing is that the viewing angle specifications are permitted to use the term "visible" until the display contrast ratio drops to an extremely low 10:1 or 5:1 when the screen is viewed from an angle (the steeper the angle from which the LCD screen is viewed, the more the contrast generally declines). In other words, they do not take into account the display uniformity of the central and peripheral areas of the screen, or the level of chromatic change, when the screen is viewed from an angle.

The ideal viewing angles is that the brightness and chromaticity is very uniform and there is not much chromatic change, even when the screen is viewed from a slight angle. The viewing angles given in the specifications are not really very helpful, but you can judge the standard of the panel type that the LCD (liquid crystal panel) adopts. IPS liquid crystal panels have the least change in brightness or chromaticity when the screen is viewed from an angle, and they are followed by VA panels. An IPS or VA liquid crystal panel can be said to indicate the superior nature of the product itself, so this is often included in the catalog or specifications. It is probably a good idea to look through the catalogs of various products.

On the other hand, monitors installed with cost-effective TN liquid crystal panels are in fact the most numerous. However, the TN type lags far behind the IPS and VA types in terms of characteristic viewing angle changes in brightness and chromaticity. Simply viewing the screen from a slightly different angle makes the coloration change dramatically, and the screen looks completely different according to whether it is viewed vertically or horizontally. If the vertical and horizontal viewing angles in the specifications are different then it is a TN type. There are quite a few products with a 20-inch wide screen or larger where colors look different in the central and peripheral areas even when the screen is viewed straight on.

The display on an IPS panel. Even when viewed from this angle, the displayed content can of course be distinguished completely and the colors also show up really well

The display on a VA panel. Compared with the IPS panel the screen is a little whitish and the chromaticity has slipped, but it is a satisfactory viewing angle for actual use

The display on a TN panel. There is a very clear difference from the IPS and VA panels. The display throughout the entire screen lacks uniformity and there is a yellow cast

The gradation images and monochrome images from earlier in this article can be used as they are to check the viewing angles. Display an image on the whole screen, look at it straight on and check whether the brightness and colors are uniform at the top and bottom of the screen, and in the center and at both sides. Then gradually shift the angle from which you view the screen and check how the brightness and coloration change. If you do this with photographic data as well as the test images, you should be able to get a better sense of the difference in the display.

When we checked the viewing angles of the FlexScan SX2462W there was absolutely nothing to criticize since, in addition to the use of an IPS panel, it is equipped with many high image quality functions, including the afore-mentioned digital uniformity correction circuit. The brightness and chromaticity throughout the whole screen is very uniform, and the coloration hardly changed at all when the viewing angle was changed.

We explained here about easy ways to check LCD monitor quality. How were the results for your current LCD? We think that many people were probably very bothered by the blocked-up shadows and blown-out highlights when the test images to check gradation were displayed, by the middle gradation banding, and by the variations in brightness and chromaticity when the monochrome images were displayed.

As we mentioned at the beginning, recently the number of LCDs with excellent display quality is on the decline. Although we would not go so far as to say that the display quality of inexpensive products is poor. Of course a high quality LCD is indispensable if you want to enjoy using your computer, properly handle the needs of applications that require color reproducibility, and to fully enjoy all the benefits of rich content.

The EIZO FlexScan LCD series has excellent display quality in those regards, and we have no qualms about recommending them to everyone. The product line-up is diverse but each model is clearly ranked according to the purpose to which it is suited and its screen size, and they all guarantee above-standard display quality. They may cost a little more than you had budgeted for but the clear value they offer exceeds their price.

If, after trying these tests, you have doubts about the display quality of the LCD that you usually use, we would certainly urge you to consider an EIZO LCD. We would also recommend that you construct a multi-display environment by making the new LCD your main monitor and the one that you have been using your sub monitor.

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

Imatest Blemish Detect uses filtering comparable to the human eye to flag visible defects while passing defects that are too small or weak to be visible. This requires careful tuning, which is explained on https://www.imatest.com/docs/blemish. Blemish detect also performs all the functions of Uniformity, which are explained in https://www.imatest.com/docs/lightfall and https://www.imatest.com/docs/lightfall_master.

For a gray screen image surrounded by a dark field (recommended; shown above), enable automatic cropping by clicking Options I and setting Blemish in the ROI (Region of Interest) section to Automatically select crop for image surrounded by a dark boundary. The largest rectangle that can fit in the screen area will be selected. (This feature is available in Imatest 3.10+.)

In addition, there are CSV, JSON, and XML output files. And very importantly, Pass/Fail criteria can be entered for testing. For example, you might set them to fail if there are more than 5 defects with more than 20 pixels (two sets of defect sizes and counts are available now).

Although Imatest is primarily orientated toward testing cameras, it includes several tests for monitors (displays). It can measure the sharpness of all sorts of displays, including flat panels, projectors, heads up displays (HUDs), virtual & augmented reality head-mounted displays (HMDs) .

We believe that the slanted-edge is the best pattern for representing a display’s visible sharpness. Slanted-edge MTF analysis is based on the widely-used and well-accepted ISO 12233 standard, which is Imatest’s primary method of measuring sharpness.

Straight vertical and horizontal edges in test images (which will be displayed parallel to the monitor pixel boundaries; found, for example, in unrotated Checkerboard images), photographed tilted, are sometimes recommended for monitor MTF measurements, but should be avoided

A downloadable SFRreg bitmap imagewith multiple slanted-edges(small file size because it’s a PNG) is shown on the right. It is derived from one of many vector graphics test patterns that can be generated by the ImatestTest Chartsmodule and rasterized usingInkscape.

Though the Imatest Screen Patterns module can be used to display a test pattern directly from Imatest, it’s not recommended because of image resizing issues on systems with multiple monitors with different scaling settings.

Camera and lens — Use a high quality mirrorless or industrial camera to photograph your display or projector image. Modern Micro Four-Thirds or APS-C mirrorless cameras work very well (full frame cameras are overkill). DSLRs are not recommended because of mirror slap, and because mirrorless cameras are now so widely available. For testing monitors, use a high quality macro (close-up) lens, preferably one with magnification on the scale (or magnification easily derived from the distance setting).

The 24 megapixel Micro Four-Thirds camera and older 60mm macro lens (with manual focus and a magnification scale) described in Compensating camera MTF measurements for chart and sensor MTF — Chart MTF measurement works very well for monitor MTF testing. The specialized camera mount is not necessary.

Underexpose the image by about 1 f-stop (using the camera’s exposure compensation setting) to avoid saturating the green pixels. Be especially careful to avoid overexposing the monitor image (which almost always happens with default auto-exposure settings). In overexposed images, monitor pixels are white when they should be red, green, and blue.

Capture both RAW and JPEG images. Sometimes aggressive image processing in JPEGs leads to saturated pixels. We’ve had slightly better results with RAW images converted with dcraw. (The difference is not great.)

Here are some images from our tests of the ASUS PB278 monitor with the A7R II/90mm TS lens at 0.29× magnification. More details in section 3, below. These were RAW images converted with dcraw. Luminance and color saturation were considerably less than the in-camera JPEG.

Important. This setting applies extra filtering to the the edge location detection so edges can be correctly detected in the presence of the monitor pixel structure. It does not affect the MTF results. The filter has been greatly improved in Imatest 2020.1. In earlier versions the structure of the monitor pixels often caused a detection failure.

The Monitor Nyquist frequency = fNyq_M= 1/(2×pixel pitch) is not reported by Imatest. For this monitor, which has a pixel pitch of 0.233 mm, fNyq_M = 2.146 cycles/mm. MTF is closely related to pixel geometry. The first MTF peak is at 4.3 Cycles/Object mm = 1/pixel pitch  = (2×fNyq_M).

In the Settings window, set MTF plot units toLW/N Pixels (PH)(or LP/N Pixels (PH)), then enter the Monitor image height (pixels) (which may be much larger than the test image) into the box labeledPicture Ht (pxls)to the right of Pixel size. From Appendix II,

TV lines are defined as the number of visibly distinguishable vertical lines measured over the height of a monitor. In this context, “Lines” refers to Line Widths (LW), where 1 cycle (Line Pair) = 2 Line Widths. This definition (Wikipedia) works well with Imatestmeasurements. For digital systems , the number of TV lines is approximately MTF20 (or better, Strictly speaking, MTF10 is closer to the Rayleigh diffraction limit, but MTF10 can be strongly affected by noise and other artifacts. MTF20P (which is less sensitive to strong software sharpening than MTF20, and usually isn’t very different from MTF10) is more robust and stable.

This worked well for me on my fussy system where the main laptop monitor and my ASUS monitor (used for these tests) have different scale factors (125% and 100%, respectively).

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...

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.

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.

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.

Poorly designed backlight. LED-backlit LCD monitors require a backlight to show the image on the screen. The position and quality of these backlight systems have an impact on the uniformity of the screen. Many monitors only have a strip of LEDs at the top or bottom of the screen and use a series of diffusion films behind the LCD panel to create an even backlight. Unfortunately, not all of these designs are made the same, and edge-type backlights will often have a visible backlight that looks like a distracting bright strip on one of the edges of the screen. However, some higher-end monitors have direct LED backlighting with LEDs placed all over the screen, resulting in better uniformity. Learn more about different types of backlights on TVs here.

Lenient manufacturing and uneven frames. LCD screens are made of many layers, and most of these are flexible. When the monitor is being built or transported, some of these layers likely bend. These can cause uneven diffusion of light which leads to clouding and backlight bleed.

Monitors use different panel technologies to produce an image. Most monitors use LCD panels, of which there are different types. VA panels are known for their high contrast ratio, so they display deep blacks, but it doesn"t mean they have good black uniformity, as seen with the AOC CQ27G2 in the When It Matters section. The more common IPS panels have a low contrast ratio, which we can see with the ASUS TUF Gaming VG27AQL1A above. On average, VA and IPS panels have about the same black uniformity, but it depends on the model. There"s also a rare third panel type, the TN panel. It usually has the worse uniformity, as you can see here.

There"s another panel technology that"s different from LED-backlit monitors: OLED. These types of displays don"t have a backlight and use self-emitting pixels to display an image. Because of this, they have perfect black uniformity with no blooming around bright objects as they can turn off individual pixels. These monitors get a perfect score of ten for our black uniformity, but there are only a handful of OLED monitors we"ve tested, as they"re more common with TVs. Below you can see what an OLED looks like compared to an LED monitor.

IPS glow refers to a specific type of uniformity issue that, as the name suggests, is most common with IPS-type LCD monitors. Unlike normal uniformity issues, the cause for IPS glow is mostly the screen"s vertical viewing angle, which is why it often appears at the corners.

If you have minor clouding, you can also try a common technique that occasionally helps. With the monitor on and displaying either a black frame or our test pattern, look for the brighter areas of the screen. Using a soft cloth, gently massage the brighter spots. It might take a while, but it can be effective. Make sure to be quite gentle, though, as pressing too hard can damage your monitor.

As your monitor heats up and gets used for the first few weeks, it can get better as internal parts settle in properly. Sometimes, just a little time can help parts that were moved in shipping get placed properly. This is also why we display a warm-up video on our monitors before testing them so that the pixels aren"t "cold".

Our black uniformity tests are different from the gray uniformity tests because we see how well the monitor displays a bright object on a dark screen. The gray uniformity tests are for displaying a single color across the screen. You can learn more about them here.

We test for the black uniformity on a monitor to see how well it displays a bright object on a dark screen. This test is important if you tend to use your monitor in a dark environment, especially when viewing content with dark scenes, like video games or movies. A monitor with bad black uniformity can get distracting. We take a photo and measure the standard deviation of the black uniformity, both with the local dimming feature enabled and disabled. A monitor"s panel technology impacts the black uniformity, but it varies between units, so no two monitors are alike.

The most common issues of Android screens are dead and stuck pixels. Dead pixels occurs when small color pigments of your screen gets busted, resulting to a black spot on your screen, while stuck pixels are color pigments of the display that are frozen, unable to change to other colors like it normally should. These issues can easily be avoided if you can detect it while the problem is still not that severe. That"s why testing your LCD display is outright important and needs to be done frequently to avoid any issues from worsening.

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.

If the screen abnormality is not present in the built-in self-test mode, see the Dell knowledge base article How to Troubleshoot Display or Video Issues on a Dell Monitor.

If the LCD built-in self-test (BIST) diagnostic test passed, the laptop LCD screen is working correctly. The display problem could be due to an outdated graphics driver or incorrect video settings. Follow the troubleshooting instructions in the Dell knowledge base article How to Troubleshoot Display or Video Issues on a Dell Laptop.

To clean the anti-static screen, we recommend using a special screen-cleaning tissue or solution that is suitable for the anti-static coating on LCD panels.

While moving the monitor, follow the instructions as described in the User Manual on how to hold the monitor. Do not put pressure directly on the LCD screen as it may cause irreparable cracks.

To run a diagnostic test on the LCD panel of a Dell laptop, see the Dell knowledge base article How to Run the LCD Built-in Self-Test on a Dell Laptop.

If the screen abnormality is not present in the integrated self-test mode, see the Dell knowledge base article How to Troubleshoot Display or Video Issues on a Dell Monitor.

Running a self-test feature check (STFC) or the built-in self-test (BIST) diagnostic on a Dell monitor is always a good practice to isolate LCD or monitor issues.

If the self-test feature check (STFC) or built-in self-test (BIST) diagnostic test passed, this indicates that the Dell monitor is functioning normally. To troubleshoot the display or video issue, see the Dell knowledge base article How to Troubleshoot Display or Video Issues on a Dell Monitor.

In this quick guide we’ll cover what Dirty Screen Effect looks like, what’s happening on a technical level, and what, if anything, you can do to get rid of it. We’ll also touch on the notion of the so-called “panel lottery” and how that plays into how clean — or dirty — your new TV screen might look.

Dirty Screen Effect (DSE) is a term that’s used to describe an LCD panel that has inconsistent luminance performance across its surface area. It can appear as random splotches, uniform lines, wide bars, and, in some cases, vignetting (a slight darkening toward the corners). DSE once plagued plasma TV panels as well. But since those are no longer in production, we’ll keep this explainer focused on LCD-based TVs.

As a reminder, any TV that uses an LED backlight also uses an LCD panel, so TVs marketed as LED, QLED, and mini-LED are all susceptible. Due to what causes DSE on a technical level, some may argue it can only apply to LCD-based TVs. However, similar effects can be seen in OLED-based displays — thus the term is often applied — so we’ll include those types of TVs as well, but address them separately.

Some DSE is severe and some is so faint you may not notice it unless you look hard for it. As a very clear example of what DSE looks like when exposed by testing slides, we’ve included an example below.

There are a number of factors stemming from the manufacturing of an LCD panel that can cause Dirty Screen Effect, from variance in backlight distribution to variance in TFT switching for sub-pixels, to variance in conductivity and/or capacitance of transparent electrodes. That’s super-nerdy, though, and the actual cause is less important than the common theme here: inconsistency.

In panel manufacturing, there are numerous variables that can be introduced that would cause an LCD panel to have groups of pixels that shine less bright than others. This variance is, unfortunately, part of the tech that makes our TVs. And the manner in which different manufacturers handle that variance is also … you guessed it: Varied.

Dirty Screen Effect also can be caused by damage to the panel in shipping or mishandling of the TV during the setup or installation process. Generally speaking, it’s recommended one avoids “pinching” or otherwise exerting pressure on the front of the TV screen.

From what I’ve seen, DSE — ranging from insignificant to severe — seems fairly common among newly manufactured LCD-based televisions, due primarily to the nature of LCD panel manufacturing. Very broadly, the less expensive a TV is, the more likely it is to exhibit some level of DSE. More expensive TVs are not immune to the issue, but some manufacturers have tighter quality assurance tolerances for their high-end products so — again, very broadly speaking — DSE tends to be less prevalent among those models.

DSE as a symptom of age is virtually impossible to track, however — again, anecdotally — I have witnessed DSE creep into a TV’s display panel slowly over time and worsen with age. I’ve seen it happen in TVs I own, TVs friends and family have owned, and TVs installed in commercial environments such as hotels and bars.

First, a warning: Once you see DSE on your TV, it’s tough to “un-see.” So, if you are happy with your TV’s performance and wish to stay that way, then you may wish to subscribe to the “ignorance is bliss” theory and forego the following tests.

If, however, you suspect that your new TV may have levels of DSE that you deem to be unacceptable, you can use this YouTube video (also posted at the top of this article) to look for signs of DSE. In our video, we not only provide testing slides that help to expose DSE, but guide you on how to spot it.

Unfortunately, there’s no way to eliminate DSE. Some websites suggest loosening the screws on the back of a TV to lessen the strain on the panel. We do not recommend this tactic as it could stand to void an active warranty. Also, it’s not very likely to work.

Most TVs offer a “game mode” which, due to its tendency to brighten everything on-screen, can help to obscure DSE. But this is really just a Band-Aid measure. The DSE is still there, but it may be less obvious. Another somewhat helpful tip to reduce the appearance of DSE in LCD panels is to view the TV from as direct an angle as possible. As you move off-axis (view a TV from an angle) DSE tends to become more obvious.

The so-called “panel lottery” refers to the game TV buyers unwittingly play when purchasing a TV. Sometimes you “win the panel lottery,” which is a way of saying that the TV you got was in especially pristine shape and shows no signs of DSE. It’s also a term used to easily express that there’s such a variance in panel quality that it’s virtually impossible you’ll win a perfect panel. In other words, it’s all up to chance.

When it comes to image processors, we also like to hold the reins. Our many years of experience go into developing our own image processors (ASIC) so we are sure to get the best out of our LCD panels.

Whether you’re reading texts, editing spreadsheets, or viewing images, EIZO office monitors always give you a clear view. This is because we carefully select the best panels for each model, given that even within the same type of LCD technology – for example, IPS panels – there are still significant differences in quality.

Our IPS panels guarantee outstanding viewing angle stability at all times. This means that you will barely notice any deviation in brightness or chromaticity, even at a slanted viewing angle.

When selecting LCD panels as we develop our business monitors, we do not focus on providers; instead, we look only for the best quality. An LCD panel ends up in an EIZO monitor model only if it has passed a rigorous quality test. This is how we make sure that you end up working with the best image quality.

Before and during the series production, we perform extended tests on the stability of the product and image quality over thousands of hours of monitor usage time.

Do you want to put the image quality of your monitor to the test? We recommend our monitor test. You can carry out 13 individual tests to check how homogenous the image display is across the entire monitor and if the text is displayed sharply. You can also check your monitor for pixel errors and get a sense of its viewing angle stability. Put your monitor to the test now!

Glass substrate with ITO electrodes. The shapes of these electrodes will determine the shapes that will appear when the LCD is switched ON. Vertical ridges etched on the surface are smooth.

A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directlybacklight or reflector to produce images in color or monochrome.seven-segment displays, as in a digital clock, are all good examples of devices with these displays. They use the same basic technology, except that arbitrary images are made from a matrix of small pixels, while other displays have larger elements. LCDs can either be normally on (positive) or off (negative), depending on the polarizer arrangement. For example, a character positive LCD with a backlight will have black lettering on a background that is the color of the backlight, and a character negative LCD will have a black background with the letters being of the same color as the backlight. Optical filters are added to white on blue LCDs to give them their characteristic appearance.

LCDs are used in a wide range of applications, including LCD televisions, computer monitors, instrument panels, aircraft cockpit displays, and indoor and outdoor signage. Small LCD screens are common in LCD projectors and portable consumer devices such as digital cameras, watches, calculators, and mobile telephones, including smartphones. LCD screens have replaced heavy, bulky and less energy-efficient cathode-ray tube (CRT) displays in nearly all applications. The phosphors used in CRTs make them vulnerable to image burn-in when a static image is displayed on a screen for a long time, e.g., the table frame for an airline flight schedule on an indoor sign. LCDs do not have this weakness, but are still susceptible to image persistence.

Each pixel of an LCD typically consists of a layer of molecules aligned between two transparent electrodes, often made of Indium-Tin oxide (ITO) and two polarizing filters (parallel and perpendicular polarizers), the axes of transmission of which are (in most of the cases) perpendicular to each other. Without the liquid crystal between the polarizing filters, light passing through the first filter would be blocked by the second (crossed) polarizer. Before an electric field is applied, the orientation of the liquid-crystal molecules is determined by the alignment at the surfaces of electrodes. In a twisted nematic (TN) device, the surface alignment directions at the two electrodes are perpendicular to each other, and so the molecules arrange themselves in a helical structure, or twist. This induces the rotation of the polarization of the incident light, and the device appears gray. If the applied voltage is large enough, the liquid crystal molecules in the center of the layer are almost completely untwisted and the polarization of the incident light is not rotated as it passes through the liquid crystal layer. This light will then be mainly polarized perpendicular to the second filter, and thus be blocked and the pixel will appear black. By controlling the voltage applied across the liquid crystal layer in each pixel, light can be allowed to pass through in varying amounts thus constituting different levels of gray.

The chemical formula of the liquid crystals used in LCDs may vary. Formulas may be patented.Sharp Corporation. The patent that covered that specific mixture expired.

Most color LCD systems use the same technique, with color filters used to generate red, green, and blue subpixels. The LCD color filters are made with a photolithography process on large glass sheets that are later glued with other glass sheets containing a TFT array, spacers and liquid crystal, creating several color LCDs that are then cut from one another and laminated with polarizer sheets. Red, green, blue and black photoresists (resists) are used. All resists contain a finely ground powdered pigment, with particles being just 40 nanometers across. The black resist is the first to be applied; this will create a black grid (known in the industry as a black matrix) that will separate red, green and blue subpixels from one another, increasing contrast ratios and preventing light from leaking from one subpixel onto other surrounding subpixels.Super-twisted nematic LCD, where the variable twist between tighter-spaced plates causes a varying double refraction birefringence, thus changing the hue.

LCD in a Texas Instruments calculator with top polarizer removed from device and placed on top, such that the top and bottom polarizers are perpendicular. As a result, the colors are inverted.

The optical effect of a TN device in the voltage-on state is far less dependent on variations in the device thickness than that in the voltage-off state. Because of this, TN displays with low information content and no backlighting are usually operated between crossed polarizers such that they appear bright with no voltage (the eye is much more sensitive to variations in the dark state than the bright state). As most of 2010-era LCDs are used in television sets, monitors and smartphones, they have high-resolution matrix arrays of pixels to display arbitrary images using backlighting with a dark background. When no image is displayed, different arrangements are used. For this purpose, TN LCDs are operated between parallel polarizers, whereas IPS LCDs feature crossed polarizers. In many applications IPS LCDs have replaced TN LCDs, particularly in smartphones. Both the liquid crystal material and the alignment layer material contain ionic compounds. If an electric field of one particular polarity is applied for a long period of time, this ionic material is attracted to the surfaces and degrades the device performance. This is avoided either by applying an alternating current or by reversing the polarity of the electric field as the device is addressed (the response of the liquid crystal layer is identical, regardless of the polarity of the applied field).

Displays for a small number of individual digits or fixed symbols (as in digital watches and pocket calculators) can be implemented with independent electrodes for each segment.alphanumeric or variable graphics displays are usually implemented with pixels arranged as a matrix consisting of electrically connected rows on one side of the LC layer and columns on the other side, which makes it possible to address each pixel at the intersections. The general method of matrix addressing consists of sequentially addressing one side of the matrix, for example by selecting the rows one-by-one and applying the picture information on the other side at the columns row-by-row. For details on the various matrix addressing schemes see passive-matrix and active-matrix addressed LCDs.

LCDs are manufactured in cleanrooms borrowing techniques from semiconductor manufacturing and using large sheets of glass whose size has increased over time. Several displays are manufactured at the same time, and then cut from the sheet of glass, also known as the mother glass or LCD glass substrate. The increase in size allows more displays or larger displays to be made, just like with increasing wafer sizes in semiconductor manufacturing. The glass sizes are as follows:

Until Gen 8, manufacturers would not agree on a single mother glass size and as a result, different manufacturers would use slightly different glass sizes for the same generation. Some manufacturers have adopted Gen 8.6 mother glass sheets which are only slightly larger than Gen 8.5, allowing for more 50 and 58 inch LCDs to be made per mother glass, specially 58 inch LCDs, in which case 6 can be produced on a Gen 8.6 mother glass vs only 3 on a Gen 8.5 mother glass, significantly reducing waste.AGC Inc., Corning Inc., and Nippon Electric Glass.

In 1922, Georges Friedel described the structure and properties of liquid crystals and classified them in three types (nematics, smectics and cholesterics). In 1927, Vsevolod Frederiks devised the electrically switched light valve, called the Fréedericksz transition, the essential effect of all LCD technology. In 1936, the Marconi Wireless Telegraph company patented the first practical application of the technology, "The Liquid Crystal Light Valve". In 1962, the first major English language publication Molecular Structure and Properties of Liquid Crystals was published by Dr. George W. Gray.RCA found that liquid crystals had some interesting electro-optic characteristics and he realized an electro-optical effect by generating stripe-patterns in a thin layer of liquid crystal material by the application of a voltage. This effect is based on an electro-hydrodynamic instability forming what are now called "Williams domains" inside the liquid crystal.

In the late 1960s, pioneering work on liquid crystals was undertaken by the UK"s Royal Radar Establishment at Malvern, England. The team at RRE supported ongoing work by George William Gray and his team at the University of Hull who ultimately discovered the cyanobiphenyl liquid crystals, which had correct stability and temperature properties for application in LCDs.

The idea of a TFT-based liquid-crystal display (LCD) was conceived by Bernard Lechner of RCA Laboratories in 1968.dynamic scattering mode (DSM) LCD that used standard discrete MOSFETs.

On December 4, 1970, the twisted nematic field effect (TN) in liquid crystals was filed for patent by Hoffmann-LaRoche in Switzerland, (Swiss patent No. 532 261) with Wolfgang Helfrich and Mart