lcd display temperature limits brands

Modern LCD screens have a great many uses. Not only are they now the system of choice for our home TVs and computers but their use in digital signage has made them a common sight in many shopping malls, airports and other locations with high quantities of people.

Even outdoor locations are no barrier to the use of modern LCD screens with outdoor digital signage a rising medium now seen in many town centers, car parks, front of stores and train station platforms.

All this out of home use means many screens operate in locations test the temperature limits of LCD displays. While waterproof screens and LCD enclosures designed for rugged applications provide the ability of the screen to operate-even in outdoor locations, one consideration often overlooked, is that of temperature.

LCD screens have a limited temperature range. Not only will the electronics inside an TV screen overheat and cause failure if the screen gets too hot, but the liquid crystal itself will begin to deteriorate under hot conditions.

The same is true of environments where temperatures fall below zero, causing a screen to stop functioning. A typical LCD TV has an operating range between 0°C (32°F) and 32°C (90°F).

Of course, many indoor and outdoor locations don’t suffer temperatures outside of this range, but many locations do and placing screens in these areas can prove challenging.

One of the problems with using a screen in hot locations is that the screen itself produces quite a bit of heat. When housed in an outdoor enclosure, the heat has to be continuously removed. While cooling fans combined with an air-vent normally carry out this task on an LCD, the need to prevent moisture from getting to the screen makes the task more complicated.

To get around this problem, specially shaped vents provide an exit for hot air while preventing rainfall and other moisture from getting in. In some locations where ambient temperatures are extremely high, screens need air conditioning to ensure they don’t exceed the maximum operating temperature.

In cold climates the opposite problem occurs. The need to keep heat in often requires insulation of the screen enclosure. Often this can trap enough of the heat generated by the screen itself to keep the internal temperature above minimum, but in some locations, even this isn’t enough. Heaters, controlled by thermostats provide extra heat in these circumstances, which enables the use of LCD displays in extremely cold locations such as ski-resorts and in Arctic regions.

Liquid crystal displays (LCD) have become an essential component to the industry of display technology. Involved in a variety of contexts beyond the indoors like LCD TVs and home/office automation devices, the LCD has expanded its usage to many environments, such as cars and digital signage, and, thus, many temperature variations as well.

As with any substance that requires a specific molecular characteristic or behavior, LCDs have an operating temperature range in which the device, if within, can continue to function properly and well. In addition to that, there is also an ideal storage temperature range to preserve the device until used.

This operating temperature range affects the electronic portion within the device, seen as falling outside the range can cause LCD technology to overheat in hot temperatures or slow down in the cold. As for the liquid crystal layer, it can deteriorate if put in high heat, rendering it and the display itself defective.

In order for the LCD panel to avoid defects, a standard commercial LCD’s operation range and storage range should be kept in mind. Without adaptive features, a typical LCD TV has an operating range from its cold limit of 0°C (32°F) to its heat limit of 50°C (122°F) (other LCD devices’ ranges may vary a bit from these numbers).

The storage range is a bit wider, from -20°C (-4°F) to 60°C (140°F). Though these ranges are quite reasonable for many indoor and even outdoor areas, there are also quite a few regions where temperatures can drop below 0°C or rise above 32°C, and in these conditions, LCDs must be adapted to ensure functionality.

Heat, can greatly affect the electronics and liquid crystals under an LCD screen. In consideration of heat, both external heat and internally generated heat must be taken into consideration.

Seen as the liquid crystals are manipulated in a device by altering their orientations and alignments, heat can disrupt this by randomizing what is meant to be controlled. If this happens, the LCD electronics cannot command a certain formation of the liquid crystal layer under a pixel, and the LED backlighting will not pass through as expected, which can often lead to dark spots, if not an entirely dark image. This inevitably disrupts the display’s readability.

Depending on the upper limit of the operation temperature range, LCD device can be permanently damaged by extreme heat. With long exposure to extreme heat, besides the destruction of the liquid crystals, battery life can shorten, hardware can crack or even melt, response time may slow to prevent even more heat generation from the device.

The LED backlight and the internal circuitry, typically TFT-based in the common TFT LCDs, are components that can generate heat that damages the device and its display. To address this concern with overheating, many devices use cooling fans paired with vents.

Some devices that are used in extremely high ambient temperatures may even require air conditioning. With air vents to carry the heat out, the device can expel it into the surroundings.

But this leads to another problem: how can moisture be prevented from entering through the vent? If moisture enters the device and high heat is present, condensation can occur, fogging the display from inside, and in some cases, short-circuiting may cause the device to turn off. In order to circumvent this issue, the shapes of the air vents are specific in a way that allows only for air movement, not forms of moisture.

In the opposite direction is extreme cold. What typically occurs in the cold is “ghosting” (the burning of an image in the screen through discoloration) and the gradual slowing and lagging of response times. Like heat-affected LCD modules, the extreme temperature can affect the liquid crystals. This layer is a medium between the liquid and solid state, so it is still susceptible to freezing.

An LCD device can be left in freezing temperatures because it will likely not be permanently damaged like in the heat, but it is important to understand the device’s limits and how to take precautions when storing the device. The standard and most common lower-bound storage range limit is -20°C, below freezing, but if possible, it would be best to keep it above that limit, or else there is still a risk of permanent damage.

If the device is not adapted for the cold, it would be good to keep it bundled up, trapping the heat within layers. However, this is only a temporary solution. Adapted, rugged devices have advantages such as screen enclosure insulation for heat level preservation and, in more extreme cases, heaters to generate extra heat to raise the internal temperature to a level above the minimum.

When selecting the appropriate module, it is necessary to understand the device’s expected primary application. The application will decide factors such as display type, environmental conditions, whether or not power consumption is a factor, and the balance between performance and cost. These factors can have an effect on the operation and storage temperature ranges for the device.

Display types have a lot of variation. Choices like alphanumeric or graphic LCD, human-machine interactive LCD modules and touchscreen panels capabilities, the width of the viewing angle, level of contrast ratios, types of backlighting, and liquid crystal alignment methods are often considered. For example, the twisted nematic LCD provides for the fastest response time at the lowest cost, but cannot offer the highest contrast ratio or widest viewing angle.

Environment-based factors must consider things besides the obvious temperature like UV exposure and humidity/moisture, as they all are necessary in finding the perfect fit extreme temperature LCD module.

Besides the LCD modules, recent new products have opened doors in wide temperature range displays, such as OLED displays. OLED displays offer better displays in regard to contrast, brightness, response times, viewing angles, and even power consumption in comparison to traditional LCD displays.

These benefits, in addition to its ability to achieve a wide temperature range, provide more options for consumers in search of high quality displays for extreme climates.

The higher the mux rate, the less time a given group of segments is being addressed , and the worse the display will look. If you refer to our "Basic Operation of an LCD" page, it is easy to see that this is not a good situation.

display will not really damage the contrast and viewing angle very much. For mux rates above 4:1, serious degradation sets in. At that point, a switch of drivers or a move to STN technology are the options.

In cooler climates, the LCD fluid will slow down and change the response time of the display. We can install transparent heater films through an optical bonding process to maintain a sleek and modern display, as well as maintain display response time. The display heater will become active when the built in sensor detects a pre-set ambient temperature. This will protect the display from becoming overheated and conserve display power. We also work with you to ensure your display is in a proper enclosure that will retain the heat generated to prevent battery drainage. E3 enhancements to wide temperature displays can operate in the most rugged environments, maintain battery life, and exceed aesthetic standards.

There are several industrial applications that require LCD displays to operate in extreme temperature environments such as in military, food processing, gas/fuel pumps, medical, manufacturing, and non-climate-controlled facilities, among others. Take note that typical monitors can only be used in environments with 0�C~50�C temperature range. UV exposure, moisture, and humidity also affect the overall temperature within a specific environment. iTech Company offers a range of LCD monitors that can function properly in a wide working temperature range from -30℃ to +80℃. These products are already proven and tested to maintain its original luminance under such temperatures.

While the range of operating temperature is a relevant consideration for the device to withstand extreme hot or cold environments, other factors must also be taken into account for the overall performance of the device. These includethe clarity of the image, environmental protection, LED backlighting, quality of the components, andvarious options available.

iTech Company’s products are equipped with these useful features to deliver great performance even in harsh working conditions. These are available in different monitor sizes and resolutions. It offers superior image quality with wide viewing angle. Some of the optional features include the touch screen functionality for interactive application and the level of brightness to ensure that the screen content is highly visible in all lighting conditions. Moreover, these wide operating temperature LCD displays are available in different types including open frame, panel mount, andchassis mount.

To understand what happens to the LCD in cold temperatures, we"ll need to go back to the basics of LCD technology. Liquid crystal displays are just like their name suggests... they contain a liquid that is housed between two layers of glass. Liquids begin to freeze as the temperature drops. As the liquid in the display freezes the response time slows down. In other words, it takes longer for the numbers and letters on the display to change (Turn ON or Turn OFF).

The best way I can think to explain the response time of the LCD in cold temperatures is a ceiling fan. When you turn OFF the ceiling fan the blades continue to turn for a few minutes, even though the power if OFF. When you turn ON a ceiling fan the blades will be at full speed in a shorter period of time. At most the blades will be at their max speed within 30 seconds. When talking about an LCD, we talk about when the display is ON (the characters can be seen) or OFF (the characters cannot be seen).

Line ‘A’ (image above) displays the amount of time it takes for a character or segment on the display to turn OFF. That is, once you turn OFF the segment, how long does it take before it disappears? The graph above shows that the character actually ‘disappears’ 3500 milliseconds (3.5 seconds) after the display is turned OFF.

Line ‘B’ (image above) displays the amount of time it takes for the character or segment to turn ON. In the above graph the segment is only 55% ‘ON’ at 8000 milliseconds (8 seconds). That means the character is only ½ (half) ON. It will look grey and not very dark. It requires more time for the display to turn ON than to turn OFF… just the opposite of a ceiling fan.

We do not recommend operating our wide temperature (extended temperature) displays below -20°C (-4°F). This is true for all segment displays (static displays or glass displays), 7 (seven) segment, 14 (fourteen) segment, and 16 (sixteen) segment LCD’s.

Alphanumeric LCD displays such as: 8x1 LCD display, 8x2 LCD display, 16x1 LCD display, 16x2 LCD display, 16x4 LCD display, 20x2 LCD display, 20x4 LCD display, 24x2 LCD display, 40x1 LCD display, 40x2 LCD display, and 40x4 LCD display will react the same way.

The LCD has been widely used in different applications, such as automotive, home appliance, medical, industrial, communication, entertainment, consumer devices, etc. It has been the most popular display technology for more than a decade after surpassing CRT. But the LCD has its genetic drawbacks, such as narrow viewing angle, slow response, and low contrast, limiting its use in some applications. These drawbacks also make LCDs venerable for other new display technologies, OLED (Organic Light Emitting Diode) and Micro LED. Engineers have been working on different ways to improve the LCD drawbacks. Today, we will discuss the LCD contrast affected by temperature and improve LCD contrast with the temperature changes.

From Figure 2, when the voltage increases, the LCD’s transmission is getting lower. When the transmission level reaches 90% of the no voltage applied, we can see the LCD shows images but very light. We call it the threshold voltage (V90 or Vth).

From Figure 3, we can see the LCD voltage decreases with the temperature. From -15oC to +60oC, the curve relatively flat, but when the temperature is lower than -20oC and higher than +70oC, the voltage changes dramatically with temperature, that is why most LCD has an operating temperature of -20oC to +70oC.  Some LCD manufacturers stated that the LCD has an operating temperature range of -30 oC to +80oC, but be ready that the poor contrast has to be accepted with both ends of the temperature.

From Figure 4, we can see the LCD contrast is optimized at a temperature of around +20oC, which is room temperature.  The contrast (CR) decreases with higher and lower temperatures, which can be a big issue for some applications.

Scientists and Engineers of different areas have been trying to improve the LCD contrast under low and high temperatures. But the facts are all of them having trade-off. The users have to balance all the factors to choose the best solutions for their applications. We will explain the most popular ways for LCD to deal with temperature.

It is easier to do. The contrast dramatically changes at a higher temperature because liquid crystal material is close to its clearing point.  The material in the LCD is no longer liquid crystal material anymore; it becomes liquid (like water). Then, the solution will be to increase the clearing point of the material used. Most commercial LCDs use liquid crystal material with a clearing point of around 80oC, making it useable at +70oC. Still, for those conditions, the liquid crystal material used as a clearing point closer to 130oC makes it useable over +100oC theoretically.

Of course, we can imagine that material is costly. Another issue that the high-temperature performance LCDs have a bad performance at low temperature. The response time at low temperatures can be very long.

The heater can be used to heat LCD when the temperature drops below -20oC. Of course, the temperature sensor can be used to switch on/off the heating. Usually, there are 3 kinds of heaters to be used. 1) wire heater, 2) ITO heater on flex, 3) ITO heater on the glass. Depending on the heating speed needed, the heating power can be designed.

Of course, you can see the issue of using a heater in an LCD. The first is the cost; the second is the power of heating. Please prepare to use around 1 to 2w/inch2 power budget in your design.

The biggest liquid crystal material manufacturer in the world, E. Merck claimed that they developed “Flat Fluids,” which makes the curve in  Figure 3 LCD Operating Voltage (Vop) vs Temperature relatively flat from -30oC to +80oC. It is good news for most applications. But the limitation is that Flat Fluids can only be used in TN-type displays also costly.

The good news that many modern LCD controllers include temperature compensation circuitry in the IC design, dramatically makes the design work easier by simply setting the function. But all the LCD temperature compensation circuitry is linear, which can’t match the liquid crystal material voltage curve with temperature. But it is good enough for most applications. See Figure 6.

Typically, standard LCD display provide a temperature range of 0°C to +50°C. However, this temperature range cannot always meet the needs of such usage. Considering the increasing demand of wide temperature range, several display manufacturers offer wide selection of standard versions that range from -20°C to +70°C. Extended Temperature Solutions for Industrial Applications. As a professional LCD manufacturer, we must follow more closely demands in the market. EVERVISION has developed a series of wide temperature TFT LCD modules with operating temperatures ranging from -30°C to +80°C, and the maximum for some models can reach 85°C. For more information, please contact us.

Expanding the operating temperature range is one of EVERVISION"s strategy to improve the performance of industrial TFT product line. The other display improvement is LCD Transparent Heater that provides optimized visual view even in an extremely low temperature environment.

As a solution, EVERVISION integrate the TFT LCD module, transparent heater(Glass Heater) and heater temperature sensor to control and monitor temperature smartly. With our controller system, it could precisely and rapidly adjust the temperature of TFT-LCD module. Also, it can reduce display power consumption.

Microtips’s Automotive Grade LCD Modules are offered in sizes ranging from 3.5 to 12.1 in. with high-brightness backlights. The units are suitable for use in applications such as dials, gauges, clocks and audio/thermostat controls. The LCD modules can be operated in -30 to 85°C and can be either resistive or capacitive. The units use IPS technology for keeping colors accurately vibrant and viewing angles wide.

These LCD Modules, with a standard operating temperature of -30 to 85 degrees Celsius, will allow manufacturers to use these displays in any environment, no matter how harsh the conditions. With an emphasis on robust construction and extended temperature range, these displays are ready to use in automotive applications like dials, gauges, clocks, and audio/thermostat controls. They are available in a variety of sizes ranging from 3.5” to 12.1” with high resolution and can come with high-brightness backlights for sunlight readability. Most utilize the latest IPS technology to keep colors accurately vibrant and viewing angles wide. These displays are available with many different interface technologies such as LVDS and RGB to ensure that our display will work with most controllers. Touch Panels are available on some models which make them perfect for center infotainment consoles. They can be either resistive or capacitive and can be fine tuned to work with gloves if needed. They utilize SPI or I2C to communicate with the host device.

Professional LCD displays are located in such industries as medical, industrial, theaters, airports, train stations, churches and even schools. They provide the ability to display information to a large body of people or are visible at a great distance. These displays produce large color images and characters that display information such as arrival and departure times and weather conditions. Information can be presented as precisely and attractively as possible.

The most common types of technology in use are TFT (Thin film transistor liquid crystal display), OLED (organic light-emitting diode) and plasma displays. All of these types of displays offer color and the ability to display graphics and characters. Many contain the ability to display video. One major disadvantage of each of these displays is their cost to be customized.

TFT, OLEDs and Plasma can be customized to meet the needs of a customer, but the tooling cost is very prohibitive. Even if the customer is willing to invest into tooling, the MOQ (Minimum Order Quantity) requirements can reach as high as several thousand. These limitations force customers looking for a professional LCD display to design their product around the LCD. This is no longer true with the introduction of a new technology that offers the ability of low cost tooling and lower MOQ’s but also a wide operating temperature range and ultra-sharp contrast.

UWVDLCD displays are built with a stark black background. Unlike other technologies that use filters to create the black, UWVD LCD displays offer a true black background 100% of the time. There is no ‘dark grey’ or fading of colors that older displays suffered from.

In the past, product design engineers using a professional LCD display were required to design their product around the display module. UWVD now reverses this; the display can be designed and manufactured to meet the needs of the customer’s product.

Professional LCD displays incorporating UWVD technology offer a contrast ratio of greater than 200:1. This contrast can be seen when the display is located a long distance from the audience or end customer.

The operating temperature range of a TFT is at -20C to +70C and plasma displays are rated to at 0C to +40C. OLED displays can operate as low as -40C, but keep in mind that half-life of the blue color is rated at 14K hours (1.6 years on continuous use).

Product design engineers making use of professional LCD displays have many choices when choosing a display technology that would be perfect for their particular product. The UWVD technology may offer a competitive advantage over other competing LCD technology.

Made for any rugged application this 7.0″ TFT comes with a high resolution of 1280x768dot, super-wide viewing angles, high brightness 1000cd, high contrast 1000:1 and a wide operating temperature range of -40 to +80C. It also manages high vibration and shock for outdoor industrial devices.

Mitsubishi Electric also offers 7.0” / 8.0” / 12.1” / 15.0” and 19” TFT with pcap-touch for rugged applications! In total they have more than 34 TFT-LCD modules with super-wide viewing angles.

LCD stands for “liquid crystal display,” but this is a bit of a misnomer. In reality, the technology has no liquid components, so it isn’t susceptible to freezing and expansion in extreme cold. (Remember, many vehicles nowadays have LCD displays on their in-dash radios and CD players, and these have not been known to crack in freezing climates.)

An LED (light-emitting diode) TV is nothing more than an LCD TV that uses LED backlighting. Compared to the LCD’s fluorescent-style backlighting, LEDs are more energy-efficient, but they don’t respond to cold temperatures much differently. One exception is that LED lights may actually shine brighter in cooler temperatures, as long as it is not too cold. But what is too cold?

When it comes to durability in cold temperatures, there is no real difference between LCD and LED TVs. An LCD or LED TV may not perform well under extreme temperature conditions. In the cold, the response time of an HDTV picture may lag. For this reason, many LCD and LED television manuals will specify a safe-operating-temperature range. In most HDTVs, this range is about 50–90°F.

The temperature range for safe storage is typically even wider. Most LCD and LED sets are rated for storage in temps as low as -4°F. Always refer to your television’s manual for actual safe-temperature ranges.

If your cabin gets colder than this in the winter, you may want to consider erring on the side of caution. Cover the set in a soft blanket to protect it from dust and direct sunlight, and then store it in a dry place with above-freezing temperatures for the season, or for however long you plan to be away.

If you decide to leave the TV at the cabin for impromptu winter visits, exercise caution when turning it on in a cold room. Allow time for the cabin to warm up before turning on the TV, otherwise the extreme change in temperature may result in condensation inside the set and subsequent damage to the screen.

So, when you arrive at the cottage and fire up the woodstove, fireplace or heater, wait at least an hour (longer is better) for the screen to reach a temperature within the safe operating range. Sounds like a long time to wait, we know. But just think – you’ll have more time for card games and conversation!

LCD Monitor Course II, which kicks off this session, will address certain points one must know to choose the LCD monitor best-suited to one"s needs from the various models available. Part 1 will focus on color gamut. While wide color gamuts are the latest trend in LCD monitors, color gamut is a term that lends itself to misunderstanding. Our hope is that this session will help users better understand the color gamut of LCD monitors and better select, use, and adjust the products.

Note: Below is the translation from the Japanese of the ITmedia article "IT Media LCD Monitor Course II, Part 1" published on November 11, 2008. Copyright 2011 ITmedia Inc. All Rights Reserved.

Various methods are used to express (diagram) the color gamut, but the common method used for display products is the xy chromaticity diagram of the XYZ color system established by the International Commission on Illumination (CIE). In an xy chromaticity diagram, the colors of the visible range are represented using numerical figures and graphed as color coordinates. In the following xy chromaticity diagram, the area shaped like an upside-down "U" surrounded by dotted lines indicates the range of colors visible to human beings with the naked eye.

Various standards govern color gamuts. The three standards frequently cited in relation to personal computers are sRGB, Adobe RGB, and NTSC. The color gamut defined by each standard is depicted as a triangle on the xy chromaticity diagram. These triangles show the peak RGB coordinates connected by straight lines. A larger area inside a triangle is regarded to represent a standard capable of displaying more colors. For LCD monitors, this means that a product compatible with a color gamut associated with a larger triangle can reproduce a wider range of colors on screen.

This is a CIE XYZ color system xy chromaticity diagram. The areas enclosed in dotted lines represent the range of colors human beings can see with the naked eye. The ranges corresponding to the sRGB, Adobe RGB, and NTSC standards defining color gamuts appear as triangles connecting their RGB peak coordinates. The color gamut of an LCD monitor"s hardware can be indicated using similar triangles. An LCD monitor is not capable of reproduction (display) of colors outside its color gamut.

The standard color gamut for personal computers is the international sRGB standard prepared in 1998 by the International Electrotechnical Commission (IEC). sRGB has established a firm position as the standard in Windows environments. In most cases, products like LCD monitors, printers, digital cameras, and various applications are configured to reproduce the sRGB color gamut as accurately as possible. By ensuring that the devices and applications used in the input and output of image data are sRGB compatible, we can reduce discrepancies in color between input and output.

Adobe RGB was defined in 1998 by Adobe Systems, maker of the well-known Photoshop series of photo-retouching software products. While not an international standard like sRGB, it has become— backed by the high market share of Adobe"s graphics applications—the de facto standard in professional color imaging environments and in the print and publishing industries. Growing numbers of LCD monitors can reproduce most of the Adobe RGB color gamut.

NTSC, the color-gamut standard for analog television, is a color gamut developed by the National Television Standards Committee of the United States. While the range of colors that can be depicted under the NTSC standard is close to that of Adobe RGB, its R and B values differ slightly. The sRGB color gamut covers about 72% of the NTSC gamut. While monitors capable of reproducing the NTSC color gamut are required in places like video production sites, this is less important for individual users or for applications involving still images. sRGB compatibility and the capacity to reproduce the Adobe RGB color gamut are key points of LCD monitors that handle still images.

The visual differences between Adobe RGB (photo at left) and sRGB (photo at right). Converting a photograph in the Adobe RGB color gamut to the sRGB domain results in the loss of highly saturated color data and loss of tonal subtleties (i.e., a susceptibility to color saturation and tone jumping). The Adobe RGB color gamut can reproduce more highly saturated colors than sRGB color. (Note that the actual colors displayed will vary with factors such as the monitor used to view them and the software environment. The sample photographs should be used for reference only.)

In general, the LCD monitors currently available for use with PCs have color gamuts capable of displaying nearly the entire sRGB gamut, thanks to the specifications for their LCD panels (and panel controls). However, given the rising demand mentioned above for reproducing color gamuts broader than sRGB, recent models have expanded the color gamuts of LCD monitors, with Adobe RGB serving as one target. But how is such expansion of LCD monitor color gamuts taking place?

Improvements in backlights account for a significant proportion of the technologies expanding the color gamuts of LCD monitors. There are two major approaches to doing this: one involves expanding the color gamut of cold cathodes, the mainstream backlight technology; the other involves RGB LED backlights.

On the subject of color-gamut expansion using cold cathodes, while strengthening the LCD panel"s color filter is a quick fix, this also lowers screen luminance by decreasing light transmissivity. Increasing the luminance of the cold cathode to counter this effect tends to shorten the life of the device and often results in lighting irregularities. Efforts to date have overcome these drawbacks to a large extent; many LCD monitors feature cold cathodes with wide color gamuts resulting from modification of their phosphors. This generates cost benefits as well, since it makes it possible to expand the color gamut without major changes in the existing structure.

Use of RGB LED backlights has increased relatively recently. These backlights make it possible to achieve higher levels of luminance and purity of color than cold cathodes. Despite certain disadvantages, including lower color stability (i.e., radiant-heat problems) than a cold cathode and difficulty in attaining a uniform white color across the entire screen, since it involves a mixture of RGB LEDs, these weaknesses have been resolved for the most part. RGB LED backlights cost more than cold-cathode backlights and are currently used in a fairly small proportion of LCD monitors. However, based on their efficacy in expanding color gamuts, the number of LCD monitors incorporating the technology will likely increase. This is also true for LCD televisions.

In passing, many LCD monitors that extol wide color gamuts promote the area ratios of specific color gamuts (i.e., triangles on the xy chromaticity diagram). Many of us have probably have seen indications of attributes such as Adobe RGB rates and NTSC rates in product catalogs.

However, these are only area ratios. Very few products include the entire Adobe RGB and NTSC color gamuts. Even if a monitor featured a 120% Adobe RGB ratio, it would remain impossible to determine the extent of the difference in RGB values between the LCD monitor"s color gamut and the Adobe RGB color gamut. Since such statements lend themselves to misinterpretation, it is important to avoid being confused by product specifications.

To eliminate problems involving labeled specifications, some manufacturers use the expression "coverage" in place of "area." Clearly, for example, an LCD monitor labeled as having Adobe RGB coverage of 95% can reproduce 95% of the Adobe RGB color gamut.

From the user"s perspective, coverage is a more user-friendly, easier-to-understand type of labeling than surface ratio. While switching all labeling to coverage presents difficulties, showing in xy chromaticity diagrams the color gamuts of LCD monitors to be used in color management will certainly make it easier for users to form their own judgments.

With regard to the difference between area labeling and coverage labeling as gauges of an LCD monitor"s color gamut, to use Adobe RGB as an example, in many cases, even a monitor with an Adobe RGB ratio of 100% in terms of area will feature coverage of less than 100 percent. Since coverage impacts practical use, one must avoid the mistake of seeing a higher figure as automatically better.

When we check the color gamut of an LCD monitor, it"s also important to remember that a wide color gamut is not necessarily equivalent to high image quality. This point may generate misunderstanding among many people.

Color gamut is one spec used to measure the image quality of an LCD monitor, but color gamut alone does not determine image quality. The quality of the controls used to realize the full capabilities of an LCD panel having a wide color gamut is crucial. In essence, the capacity to generate accurate colors suited to one"s own purposes outweighs a wide color gamut.

When considering an LCD monitor with a wide color gamut, we need to determine if it has a color-gamut conversion function. Such functions control the LCD monitor"s color gamut based on the target color gamut, such as Adobe RGB or sRGB. For example, by selecting sRGB mode from a menu option, we can adjust even an LCD monitor with a wide color gamut and high Adobe RGB coverage so that the colors displayed on screen fall within the sRGB color gamut.

Few current LCD monitors offer color-gamut conversion functions (i.e., feature compatibility with both Adobe RGB and sRGB color gamuts). However, a color-gamut conversion function is essential for applications demanding accurate color generation in the Adobe RGB and sRGB color gamuts, such as photo retouching and Web production.

For purposes requiring accurate color generation, an LCD color monitor lacking any color-gamut conversion function but having a wide color gamut can actually be a disadvantage in some cases. These LCD monitors display each RGB color mapped to the color gamut inherent to the LCD panel in eight bits at full color. As a result, the colors generated are often too vivid for displaying images in the sRGB color gamut (i.e., the sRGB color gamut cannot be reproduced accurately).

Shown here are examples of an sRGB color gamut photograph displayed on an sRGB-compatible LCD monitor (photo at left) and on an LCD monitor with a wide color gamut but incompatible with sRGB and with no color-gamut conversion function (photo at right). While the photograph at right appears vivid, saturation is unnaturally high in parts of the photo. We also see a significant departure from the colors envisioned by the photographer, as well as so-called memory colors.

In more than a few cases, as expanding LCD monitor color gamuts result in the capacity to reproduce a wider range of colors and more opportunities to check colors or adjusting images on monitor screens, problems such as breakdowns in tonal gradations, variations in chromaticity caused by narrow viewing angles, and screen display irregularities, less conspicuous at color gamuts in the sRGB range, have become more pronounced. As mentioned earlier, the mere fact of incorporating an LCD panel with a wide color gamut does not ensure that an LCD monitor offers high image quality. On this subject, let"s take a close look at various technologies for putting a wide color gamut to use.

First we look at technologies to increase gradation. Key here is the internal gamma-correction function for multi-level gradation. This function displays eight-bit input signals on screen in each RGB color from the PC side after first subjecting them to multi-level gradation to 10 or more bits in each RGB color inside the LCD monitor, then assigning these to each RGB eight-bit color deemed optimal. This improves tonal gradations and gaps in hue by improving the gamma curve.

On the subject of the viewing angle of an LCD panel, while larger screen sizes generally make it easier to see differences, particularly with products with wide color gamuts, variations in chromaticity can be an issue. For the most part, chromaticity variation due to viewing angle is determined by the technology of the LCD panel, with superior ones showing no variation in color even when viewed from a moderate angle. Setting aside the various particulars of LCD panel technologies, these generally include in-plane switching (IPS), vertical alignment (VA), and twisted nematic (TN) panels, listed from smaller to larger chromaticity variation. While TN technology has advanced to the point at which viewing angle characteristics are much improved from several years back, a significant gap remains between this technology and VA and IPS technologies. If color performance and chromaticity variation are important, VA or IPS technology remains the better choice.

A uniformity-correction function is a technology for reducing display irregularities. The uniformity referred to here refers to colors and brightness (luminance) on screen. An LCD monitor with superior uniformity has low levels of screen luminance irregularities or color irregularities. High-performance LCD monitors feature systems that measure luminance and chromaticity at each position on screen and correct them internally.

This is a comparison of monitors with and without uniformity correction. An LCD monitor with uniformity correction (photo at left) has more uniform luminance and color on screen than one lacking uniformity correction (photo at right). The two photographs above have been adjusted to equalize levels to emphasize display irregularities. Actual irregularities would be less conspicuous.

To make full use of an LCD monitor with a wide color gamut and to display colors as the user intended, one needs to consider adopting a calibration environment. LCD monitor calibration is a system for measuring colors on screen using a special-purpose calibrator and reflecting the characteristics of the colors in the ICC profile (a file defining device color characteristics) used by the operating system. Going through an ICC profile ensures uniformity between the color information handled by graphics software or other software and the colors generated by the LCD monitor to a high degree of precision.

Software calibration refers to following the instructions of specialized calibration software to adjust parameters such as luminance, contrast, and color temperature (RGB balance) using the LCD monitor"s adjustment menu, approaching the intended color through manual adjustments. Graphics driver colors are manipulated in some cases in place of the LCD monitor"s adjustment menu. Software calibration features low cost and can be used to calibrate any LCD monitor.

However, variations in precision can arise since software calibration involves manual adjustment. Internally, RGB gradation can suffer because display balance is matched by thinning RGB output levels using software processing. Even so, use of software calibration will likely make it easier to reproduce colors as intended than using no calibration at all.

In contrast, hardware calibration is clearly more precise than software calibration. It also requires less effort, although it can be used only with compatible LCD monitors and entails certain setup costs. In general, it involves the following steps: calibration software controls the calibrator; matching color characteristics on screen with target color characteristics and directly adjusting the LCD monitor"s luminance, contrast, and gamma-correction table (look-up table) at the hardware level. Another aspect of hardware calibration that cannot be overlooked is its ease of use. All tasks through the preparation of an ICC profile for the results of adjustment and registering this to the OS are done automatically.

The EIZO LCD monitors currently compatible with hardware calibration include models in the ColorEdge series. The FlexScan series uses software calibration. (Note: As of January 2011, FlexScan monitors compatible with EasyPIX ver. 2 offer hardware calibration functionality.)

In the next session, we will examine LCD monitor interfaces and a number of video interfaces for LCD monitors, including the latest generation of interfaces such as HDMI and DisplayPort.