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LG OLED TV Display Technology Shoot-Out

 

Dr. Raymond M. Soneira

President, DisplayMate Technologies Corporation

 

Copyright © 1990-2013 by DisplayMate Technologies Corporation. All Rights Reserved.

This article, or any part thereof, may not be copied, reproduced, mirrored, distributed or incorporated

into any other work without the prior written permission of DisplayMate Technologies Corporation

 

 

 

Introduction

Displays with Organic Light Emitting Diodes, OLEDs, are the most interesting and promising new display technology in over a decade – possibly ever. In a span of just a few years this new display technology has improved at a very impressive rate, first challenging and now surpassing the performance of the best LCD and Plasma displays. OLEDs are an entirely different and new form of display technology – they are very thin solid state displays that emit colored light directly, while LCDs use a Liquid Crystal that regulates light transmission from a separate backlight, Plasmas use an ionized gas with phosphors, and CRTs use an electron beam in a vacuum with phosphors.

 

While there have been quite a few experimental and prototype OLED displays shown over the last 5+ years, including an 11 inch 960x540 pixel TV by Sony, OLEDs first appeared in actual consumer products as 4 to 8 inch displays in Smartphones and Tablets beginning in 2010. However, producing a large screen OLED TV is considerably more difficult for many reasons – for one, a 55 inch TV screen has 121 times the area of a 5 inch Smartphone. This results in major production and technology issues, particularly in manufacturing yield and cost.

 

There are currently only two manufacturers that have begun production of OLED TVs: LG and Samsung. The TVs are based on somewhat different OLED technologies. This article examines the LG OLED TV. LG provided DisplayMate Technologies an early production OLED TV (model 55EA9800) with a 55 inch (1.4 meter) screen to test and analyze for this article. Over the past few weeks we have performed an extensive series of Lab tests and viewing tests to evaluate the LG OLED TV technology and picture quality, and also to compare it to existing LCD and Plasma TVs. We’ll cover these issues and much more, with in-depth comprehensive display tests, measurements and analysis that you will find nowhere else.

 

This will be a two-part article: this first article is devoted to explaining the unique performance capabilities of the OLED TV, with only general comparisons with LCD and Plasma TVs. In Part II we will provide detailed Lab measurements and side-by-side performance comparisons with an LCD TV and a Plasma TV. Before we begin the technical analysis, here are several other important issues…

 

There are No LED TVs!

The first thing we need to clear up is the confusion created by the marketing of “LED TVs” – there aren’t any! The so-called LED TVs are just LCD TVs that have a backlight that is made of white LED lights. The LEDs are not the display, just the backlight, nothing more! OLEDs are an entirely different emissive imaging display technology (that doesn’t use a backlight). Unfortunately, many people think they already have an LED/OLED TV at home, but they actually have an LCD TV…

 

Design Features

Several design features immediately standout with this OLED TV: it has a slightly curved screen, the screen is incredibly thin at just 0.16 inches (4.3 mm), it has an elegant curved transparent base, a dark black rimless screen without a bezel, and a small 0.4 inch (1 cm) flush border surrounding the picture to the outer edge of the screen. Even the rear of the TV looks elegant with a patterned design on a high-tech Carbon Fiber Reinforced Polymer that provides a light weight and high-strength backing for the OLED screen.

 
Curved Screen

The screen on the LG OLED TV is slightly curved, which has generated lots of commentary. One reason for curving the screen is just because it can be done with OLEDs, while LCDs and Plasmas cannot (although some LCD TVs were recently introduced with curved glass screens). So it’s a new design element that provides some flair and notoriety. But… the screen is just slightly curved, with a radius of curvature of 16.4 feet (5.0 meters), so the corners of the screen are only 1.4 inches (3.6 cm) forward of the rear (center) of the screen – so it’s not a large geometrical effect – just the right amount to significantly improve display performance as described below. The promotional photo at the top of the article is designed to emphasize the curves… The photo below is closer to an actual frontal view.

 

 

Whether you prefer a curved or flat screen is primarily subjective, but the slightly curved screen does provide several important objective advantages:

 

First and foremost, the concave screen shape cuts down on reflections from surrounding ambient light two ways: by reducing the screen’s 180 degree opening angle, which eliminates reflections from some ambient lighting on the sides, and also from specular (mirror) reflections off the concave screen, which directs some reflected ambient light from behind the viewers away from their line of sight. This is very important for a display technology that produces excellent dark image content and perfect blacks – because you don’t want that spoiled by ambient light reflected off the screen.

 

The slight curvature reduces visual geometric distortion: When you watch a perfectly flat TV screen, the corners of the screen are further away than the center so they appear smaller. As a result, the eye doesn’t see the screen as a perfect rectangle – it actually sees dual elongated trapezoids, which is keystone geometric distortion. The slight curvature on the LG OLED TV reduces this subtle keystone geometric distortion by 50 percent at a typical 8 foot (2.4 meter) viewing distance.

 

The slight curvature improves viewing from the sides away from the central sweet spot: A second and more subtle point: people sitting off to the sides away from the central sweet spot actually get a somewhat better viewing experience than with a flat screen because the curved screen accommodates their viewing direction better by compensating for some of the uneven image foreshortening that is seen with a flat screen: the image on the side of the screen closest to you appears larger, and the image on the side of the screen furthest away appears smaller. The inward curvature of the screen compresses the foreshortening of the image on the near side that appears larger, and the curvature on the far side enlarges the distant part of image that appears smaller, which improves the overall screen image geometry that is seen away from the central sweet spot.

 

The flip side is that the top and bottom of the screen and picture don’t look perfectly straight, but rather appear with a slight subtle curve – it’s a small geometric effect, only a 1.5% curve (difference between the center and sides) is seen at an 8 foot (2.4 meter) viewing distance. It’s more apparent when the room lights are on, but much less so in low ambient lighting, which is the best way to watch the TV. I found that if I didn’t make a point of looking for the slight curvature, I didn’t notice it. For me, the advantages of reduced reflections and better side viewing outweigh noticing a slight curvature, but it is none-the-less still a subjective call…

 

It is important to emphasize that the curvature is subtle, just 1.4 inches (3.6 cm) on a 55 inch (1.4 meter) screen. That is just the right amount to significantly improve the picture quality as described above. Reviewers who have said the opposite, that the curvature interferes with multiple viewers or viewing away from the central sweet spot have clearly not spent much (or any) time actually viewing (and testing) this curved screen TV.

 

Pricing

Brand new technologies always start out very expensive – and this first generation 55 inch (1.4 meter) LG OLED TV is no exception at $9,999 US (€8,999 Euros), which is comparable to the initial pricing for large Plasma TVs when they first came out. Given the limited production, even at this high price point LG will still be able to sell every one they can make. As the OLED TV technology is refined and production yields increase the price will steadily come down. At some time in the future – which will take years – OLED TVs will become cheaper to make than LCDs and Plasmas because they are considerably less complicated to manufacture and assemble. An LCD display panel, for example, consist of dozens of separately manufactured components that are assembled like a car on an assembly line, whereas OLED displays are manufactured more like a large semiconductor chip.

 

Overview and Summary of Results

OLEDs provide a number of major technology enhancements for displays and TVs: high Peak Brightness together with perfect Blacks, Infinite Contrast Ratios, very wide Viewing Angles, and very fast Response Times without visible Motion Blur. But what makes this TV absolutely stunning is combining that with a very accurate factory calibration that takes full advantage of the OLED display technology and delivers picture quality and accuracy that is visually indistinguishable from perfect based on our extensive Lab tests. Below is an Overview and Summary of the extensive Lab and Viewing Tests followed by the LG OLED TV Conclusions.

 

We have also provided a Lab Measurements and Technical Analysis section that has detailed technical information and data on: White Sub-pixels, Brightness and Contrast Ratio, Screen Reflectance, JNCD Just Noticeable Color Difference, Color Gamuts, Absolute Color Accuracy, Intensity Scale and Image Contrast, Color Tracking Accuracy, Changes with Viewing Positions and Viewing Angles, Response Time and Motion Blur, Stuck or Dead Pixels, Screen Saver, and Power Consumption.

 

LG OLED TV Technology

This LG TV has some unique OLED technology. First of all, rather than laying out a matrix of separate Red, Green, and Blue OLED sub-pixels throughout, the TV has a uniform set of WRGB sub-pixels that are made as a stack of various colors of OLEDs. This approach simplifies the OLED production, improves yields, and lowers the manufacturing cost. A set of Red, Green and Blue sub-pixel filters, which LG calls a Color Refiner, recovers the desired Red, Green and Blue OLED colors for each sub-pixel. This approach also improves Viewing Angle performance, which is outstanding. LG has also added a 4th clear sub-pixel to every pixel, which produces pure White. This increases the display’s power efficiency and also improves color accuracy and color management. See the Lab Measurements and Technical Analysis section for more information on White Sub-pixels. Lastly, the OLED pixels are all driven by an Active Matrix IGZO Metal Oxide backplane. The Refresh Rate for the display is 120 Hz. Not surprisingly, it’s a cutting edge state-of-the-art display throughout…

 

Picture Modes

This TV comes with 6 different preset Picture Modes for viewers to choose from: Vivid, Standard, Eco, Game, ISF Expert and THX Cinema. The THX Cinema and ISF Expert picture modes both deliver close to a visually perfect TV calibration that we will examine in detail below. The Certified THX Cinema mode has no user adjustable controls or options, including brightness, and is designed for viewing under specified low ambient light viewing conditions. The two ISF Expert modes provide lots of user adjustments, but the TV is so well calibrated that “OLED Brightness” and Color (saturation) are the only two that should be adjusted based on individual viewer preferences. The Standard, Eco, Game, and Vivid Picture Modes offer a peppier picture with more color, image contrast, and dynamic image processing. The TV also has 3D modes, and it comes with four pairs of light weight designer 3D glasses that look and wear like fashionable sunglasses. We’ll cover these modes in depth below.

 

Brightness

This OLED TV delivers a Peak Brightness that is comparable to the brightest large screen LCD TVs for TV, movie, and video content. While the THX Cinema mode has an intentionally low Luminance of 135 cd/m2 for viewing under low ambient lighting, the equally well calibrated ISF Expert modes go up to 308 cd/m2, which is impressively bright for an accurately calibrated TV. The Standard, Vivid, Game, and Eco modes deliver up to 372 cd/m2. When using the TV for watching typical web and computer content, which often have lots of bright white content, the Peak Brightness can decrease to 110 to 140 cd/m2, which is bright enough for comfortable viewing in all but the highest ambient light. See the Lab Measurements section for details.

 

Screen Reflections
The screens on all displays are mirrors that reflect light from everything that is illuminated anywhere in front of the screen (especially anything behind the viewers), including lamps, ceiling lights, windows, direct and indirect indoor and outdoor sunlight, which washes out the on-screen colors, degrades image contrast, and interferes with seeing the on-screen images. This is especially important for OLED displays because they produce excellent dark image content and perfect blacks – you don’t want that spoiled by ambient light being reflected off the screen. The LG OLED TV has the lowest screen Reflectance of any display that we have ever measured, just 2.2 percent, which is half of the previous 4.4 percent record – an impressive achievement. LG accomplished this by using both an anti-reflection screen treatment together with circular polarizers that suppress light reflections (which are part of the TV’s 3D FPR optics, below).
 
We visually verified the very low Reflectance by holding an iPad Air with 6.5 percent Reflectance and an Amazon Kindle Fire HDX 8.9 with 5.0 percent Reflectance right in front of the LG OLED TV screen. The reflections from the OLED TV screen were considerably darker, which was quite striking. Low Reflectance really does make a significant and visually noticeable difference!

 

Color Calibration and Accuracy

The detailed Lab Measurements section shows that the THX Cinema and ISF Expert modes are calibrated so accurately that they are visually indistinguishable from perfect. The Color Gamut is 99% of the sRGB/Rec.709 Standard. The White Point, Primary Colors, Reference Colors, and Color Tracking Accuracy are all close to 1 JNCD (Just Noticeable Color Difference), so the eye sees them as visually indistinguishable from perfect – which was confirmed in the Viewing Tests. See the Lab Measurements section for details and explanations of JNCD and Absolute Color Accuracy.

 

Viewing Angle Performance

The best place to watch any display is with the viewer sitting directly in front of the center of the screen at eye height – which is called the “sweet spot” and only one person can be there. Other viewers may see a slight to substantial degradation depending on how far away they are from the sweet spot. In many cases TV viewers watch from 30 degrees and occasionally as high as 45 degrees Viewing Angle. All displays show some variation in Brightness, Black Level, Contrast Ratio, Intensity Scale, Gamma, White Point, Color Gamut, and Color Shifts with Viewing Angle. The variations are generally quite large for LCDs. For the LG OLED TV the Lab Measurements show no visually detectable variation in picture accuracy for typical TV watching Viewing Angles up through at least ±30 degrees. See the Lab Measurements section for details.

 

No Motion Blur

For the OLED TV high speed screen shots of fast moving test patterns show absolutely no visible display based Motion Blur or latent images from any previous refresh cycles due to a very fast Response Time. A comparison screen shot for an LCD TV shows considerable Motion Blur. For details and the screen shots see Response Time and Motion Blur in the Lab Measurements section.

 

Viewing Tests

Before, during, and after the Lab Tests we spent a considerable amount of time viewing real TV, movie and video content, lots of digital photos, plus web and computer content via its Smart TV interface. We also invited over a dozen people to come watch and provide their impressions of the OLED TV while viewing their chosen TV shows and Blu-ray movies. We also looked at lots of personal digital photos on this accurately calibrated TV, which is especially important because people generally know exactly what the photo content actually looks like – so Absolute Color Accuracy matters the most with your own digital photos. We carefully setup the viewing area with adjustable low to medium ambient lighting, a viewing distance of 8 feet (2.4 meters) and the center of the TV at viewing eye height level. The viewer comments were unanimous, “this is the best TV we have ever seen.” It’s the result of an excellent calibration that delivers accurate colors and excellent image contrast together with perfect Black Levels, which was particularly noticeable with dark content and dark picture detail that is seldom reproduced well by other display technologies (see below). Simply stated, the picture quality is absolutely stunning!

 

3D Picture Quality

This OLED TV also has 3D modes using LG’s 3D FPR technology with Passive 3D Glasses. Back in 2011 we did an article on 3D TV Technology with in-depth objective scientific comparisons and analysis, including extensive lab measurements and viewing tests together with quantifiable 3D Visual Sharpness Tests. Our 2011 study only had LCD TVs. As a result, we expected this LG OLED TV to perform better in 3D because of its improved Black Levels, Contrast Ratio, Response Time, and screen optics. We didn’t do any 3D Lab measurements this time, but viewing the same set of 3D movies mentioned in the 3D TV article produced even better 3D as we had expected. The Avatar and IMAX 3D movies that we watched were immersive and gorgeous!

 

Comparison with LCD TVs

LCDs are currently the dominant display technology because they do lots of things very well. One area where LCDs are clearly number one is in Peak Brightness (because their separate backlight can be easily brightened). The LG OLED TV has a Peak Brightness comparable to the brightest LCD TVs, but only for Average Picture Levels (APL) below 30%, which is typical for essentially all TV, movie and video content. Above 30% APL, which is common for web and computer content with white backgrounds, the OLED Brightness decreases but the LCD Brightness remains unchanged. Other than Peak Brightness at high APL the OLED TV significantly outperforms all LCDs in every other category including Black Levels, Contrast Ratio, Viewing Angles, and Response Time. We’ll cover LCD TV performance in detail in Part II of the article.

 

Comparison with Plasma TVs

Plasma TVs have traditionally had a smaller market share, but they are often preferred by video enthusiasts over LCDs because of their superior Black Levels, Contrast Ratios, Viewing Angles, and Response Time. However, Plasma displays produce visible image noise at dark intensity levels, which compromises their picture quality, whereas OLED displays do not. The OLED TV clearly outperforms Plasmas in all of the above categories, especially when viewing dark image content. In addition, Plasma TVs typically have peak Brightness (Luminance) levels of 100 to 200 cd/m2, whereas the OLED TV produces roughly double that value, even on the accurately calibrated ISF Expert picture modes. OLEDs will clearly become the preferred technology for video enthusiasts. We’ll cover Plasma TV performance in detail in Part II of the article.

 

In-depth Technical Information

We have also provided a Lab Measurements and Technical Analysis section for in-depth technical information and data on: White Sub-pixels, Brightness and Contrast Ratio, Screen Reflectance, JNCD Just Noticeable Color Difference, Color Gamuts, Absolute Color Accuracy, Intensity Scale and Image Contrast, Color Tracking Accuracy, Changes with Viewing Positions and Viewing Angles, Response Time and Motion Blur, Stuck or Dead Pixels, Screen Saver, and Power Consumption.

 

LG OLED TV Conclusions

OLEDs are the most interesting and promising new display technology in over a decade – possibly ever. In a span of just a few years this new display technology has improved at a very impressive rate, first challenging and now surpassing the performance of the best LCD and Plasma displays. OLED technology provides a number of major technology enhancements for displays: high Peak Brightness together with perfect Blacks, Infinite Contrast Ratios, very wide Viewing Angles, and very fast Response Times without visible Motion Blur. Equally impressive is that OLEDs have now moved up from small mobile displays into large TV screens for the living room.

 

But what makes this LG TV absolutely stunning is the combination of OLED display technology together with a very accurate factory calibration that delivers picture quality and accuracy that is visually indistinguishable from perfect based on our extensive Lab tests – a commendable and impressive achievement!

 

Another notable milestone is that this first generation OLED TV is already outperforming the established and highly refined LCD and Plasma technologies. Normally it takes at least 5 years for that to happen, so a lot has been going on behind the scenes… The biggest remaining challenge is to improve OLED TV production so that the price can come down as quickly as possible to more affordable levels. OLED TVs will eventually become cheaper to make than LCDs and Plasmas because they are considerably less complicated to manufacture and assemble. I can’t wait to see that happen…

 

See the Lab Measurements and Technical Analysis section for in-depth technical information and data on the LG OLED TV.

 

 

LG OLED TV Lab Measurements and Technical Analysis

Below we analyze the LG OLED TV model 55EA9800 using a wide range of Laboratory measurement data and objective evaluation criteria.

 

White Sub-pixels

Every pixel on the LG OLED TV also has a 4th independent pure White sub-pixel in addition to the standard Red, Green and Blue sub-pixels found on other displays – that’s an extra 2.1 million sub-pixels, bringing the total up to 8.3 million. In principle, they aren’t necessary because White can be produced by the other sub-pixels, but White sub-pixels provide a number of key advantages: they improve color management that allows the Color Gamut to be easily adjusted, they improve the color balance of the White Point, particularly for the crucial Color Tracking accuracy of the gray scale, and they significantly improve the power efficiency of the display because a single sub-pixel is needed to make the underlying gray component of every pixel instead of powering three Red, Green and Blue sub-pixels to do the same job. Other displays also have White sub-pixels, but they are always used to boost brightness at the expense of color saturation and accuracy – LG is the first manufacturer I am aware of to use White sub-pixels to improve color accuracy rather than decrease it…

 

Brightness and Contrast Ratio

To fully appreciate the excellent picture quality of this TV, it should be viewed under relatively low ambient lighting because ambient light washes out the excellent picture quality, image contrast, perfect blacks, and colors. The Brightness (technically the Luminance) is measured with a Spectroradiometer in units of cd/m2, sometimes referred to as nits. Under these conditions the Brightness should be set rather low, typically 150 cd/m2 or less. But when the TV is being viewed in a bright area, like a sunroom during the day, the brightness needs to go way up, sometimes as high as possible. The brightest large screen LCD TVs typically deliver 300 to 400 cd/m2, and Plasma TVs typically deliver 100 to 200 cd/m2. For OLEDs, Plasmas, and some LCDs the brightness depends on the picture content, typically the Average Picture Level, APL. Typical TV, movie and video content has around 20% APL. Web and computer content with lots of white background have higher APLs around 50-75%.

OLED TV Test Result: For typical TV, movie and video content, the THX Cinema mode Peak Brightness is fixed at 135 cd/m2, the ISF Expert mode peak Brightness goes up to 308 cd/m2, which is impressively bright for an accurately calibrated TV. For the Standard, Vivid, Game and Eco modes the peak Brightness goes up to 372 cd/m2. When using the TV for watching typical web and computer content with lots of white background the Peak Brightness can decrease to 110 to 140 cd/m2, which is bright enough for comfortable viewing in all but the highest ambient light.

 

Screen Reflectance
The screens on all displays are mirrors that reflect light from everything that is illuminated anywhere in front of the screen (especially anything behind the viewers), including lamps, ceiling lights, windows, direct and indirect indoor and outdoor sunlight, which washes out the on-screen colors, degrades image contrast, and interferes with seeing the on-screen images. This is especially important for OLED displays because they produce excellent dark image content and perfect blacks – you don’t want that spoiled by ambient light being reflected off the screen.
Reflectance Test Results: Using an Integrating Hemisphere and Spectroradiometer we measured an Average Screen Reflectance of 2.2 percent for the LG OLED TV, the lowest we have ever measured for any display. The Specular (Mirror) Reflectance was also very low at 2.7 percent. We measure that with a Spectroradiometer using a narrow collimated pencil beam of light that is reflected off the screen. LG accomplished this by using both an anti-reflection screen treatment together with circular polarizers that suppress light reflections (which are part of the TV’s 3D FPR optics).

 

JNCD Just Noticeable Color Difference

The on-screen colors produced by any display can be measured using a Spectroradiometer together with our DisplayMate Test Patterns. The accuracy of the colors can then be calculated using the 1976 CIE Uniform Chromaticity color space and compared to the eye’s sensitivity to color. We present the color errors here in terms of MPCD Minimum Perceptible Color Difference or JNCD Just Noticeable Color Difference, where 1 MPCD = 1 JNCD = Δ(u’v’) = 0.0040 on the CIE 1976 Uniform Chromaticity Scale. Color errors less than 1 JNCD are visually indistinguishable, while values greater than 1 JNCD are visually noticeable when the two colors are touching on-screen. When the colors are not touching and further apart, the threshold is higher. Here we will use 3 JNCD for a visually noticeable display color error.

Color Test Results: JNCD provides an accurate and objective way to evaluate the color accuracy of the display in terms of the eye’s sensitivity to color. All of our color results below are presented in terms of JNCD. Any Color Accuracy or Color Error less than 3 JNCD is visually indistinguishable from perfect.

 

Color Gamuts

The Color Gamut is the range of colors that a display can produce. Essentially all current consumer image content is created using the sRGB and ITU-R BT.709 (Rec.709) standards. If you want to see accurate image colors then the display must match the standard that was used to create the content. Note that standard consumer content does not include colors outside of the standard sRGB/Rec.709 Gamut, so a display with a wider Color Gamut cannot show colors that are not in the original and only produce inaccurate exaggerated on-screen colors. The color accuracy of the images produced by a TV will depend on how closely it reproduces the colors of the sRGB/Rec.709 color space. See Figure 1 below and this Link for an explanation of the Figure and the CIE Color Space.

OLED TV Test Result: The Color Gamut for the THX Cinema and ISF Expert modes is 99% of sRGB/Rec.709, which is visually indistinguishable from perfect. For the other Picture Modes the default Gamut is 116% of sRGB/Rec.709, which is designed to produce somewhat over-saturated colors, which may be a personal preference for some viewers, but can also help in high ambient light because it helps compensate for washed out image colors. A menu option allows the default Color Gamut to be changed.

 

Figure 1.  OLED TV Color Gamuts

Click Here for Details

 

Figure 2.  Absolute Accuracy Reference Colors

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Figure 3.  OLED TV Intensity Scales

Click Here for Details

 

Absolute Color Accuracy

The overall Absolute Color Accuracy of the TV was measured with a set of 10 Reference Colors that are on the periphery of the standard Color Gamut as shown in Figure 2 and this Link for an explanation of the Figure. In addition, an accurate Reference Color for the White Point in the middle of the Color Gamut is essential for reproducing all of the interior colors (together with an accurate Intensity Scale, below). The Standard White is known as D6500 (technically D65).

OLED TV Test Result: For the THX Cinema and ISF Expert modes the measured color of White is within 0.6 JNCD of D6500. The average color error for all Reference Colors is 1.3 JNCD. Both are visually indistinguishable from perfect. The other picture modes are not intended to produce very accurate colors, so we did not measure their accuracy.

 

Intensity Scale and Image Contrast

The Intensity Scale (sometimes called the Gray Scale) not only controls the contrast within all displayed images but it also controls how the Red, Green and Blue primary colors mix to produce all of the on-screen colors. So if the Intensity Scale doesn't follow the Standard that is used in all consumer content then the colors and intensities will be wrong everywhere. The steeper the Intensity Scale the greater the image contrast and the higher the saturation of displayed color mixtures. If you want to see accurate image contrast and color balance then the display must match the standard Intensity Scale that was used when creating the content, which is a mathematical power-law with a Gamma exponent of 2.2. See Figure 3 above and this Link for an explanation of the Figure and the Intensity Scale.

OLED TV Test Result: The measured Intensity Scales for the indicated Picture modes are shown in Figure 3 along with the Standard Intensity Scale with a Gamma of 2.2, which is the straight black line in the log-log graph. The measured Gammas for the Picture modes are: 2.18 for THX Cinema, 2.24 for ISF Expert, and 2.19 for the Standard mode. All are very close to the Standard Gamma of 2.2 and are effectively indistinguishable from perfect.

 

Color Tracking Accuracy

The independent Red, Green and Blue primaries on all displays need to be accurately adjusted during calibration so that all three are exactly in balance for all brightness and signal levels, otherwise images will show noticeable color imbalance errors that produce visible color tinting and color casts. The degree of imbalance is called a Color Tracking Error. As mentioned above, the White sub-pixels guarantee that there is no such error in the Gray Scale. We did an additional series of tests that examine the color balance and tracking between all possible combinations of the primaries: red-green, red-blue, and blue-green. This is a much more revealing and sensitive test than the traditional Gray Scale tracking.

OLED TV Test Result: The average Color Tracking Error all the way down to 3% of Peak Luminance is just 1.1 JNCD, which means the Color Tracking Accuracy is visually indistinguishable from perfect.

 

Changes with Viewing Positions and Viewing Angles

The best place to watch any display is with the viewer sitting directly in front of the center of the screen at eye height – which is called the “sweet spot” and only one person can be there. Other viewers may see a slight to substantial degradation depending on how far away they are from the sweet spot. All displays show some variation in Brightness, Black Level, Contrast Ratio, Intensity Scale, Gamma, White Point, Color Gamut, and Color Shifts with Viewing Angle. At 30 degrees Viewing Angle, LCDs typically show a 60 percent decrease in Brightness, a 50% decrease in Contrast Ratio, a significant change in the Intensity Scale and Gamma. Plasmas and IPS LCDs show small color shifts with Viewing Angle but many other LCD technologies show large color shifts of 10 JNCD or more at 30 degrees.

OLED TV Test Result: At 30 degrees Viewing Angle the Brightness decreased by only 1%, the Black Level was still zero, the Contrast Ratio still Infinite, the Intensity Scale and Gamma were effectively unchanged, the White Point changed by 2.3 JNCD, the Color Gamut changed by only 0.5%, and the Reference Colors shifted by an average of 1.7 JNCD. So there is no visually detectable variation in picture accuracy for typical TV watching Viewing Angles up through at least ±30 degrees.

 

Response Time and Motion Blur

Motion Blur is a well known issue with LCDs. It arises because the liquid crystal, which is the active element within an LCD, is unable to change its orientation and transmission rapidly enough when the picture changes from one frame to the next. OLEDs, as solid state emissive devices, have very fast Response Times: LG specs the OLED Response Time at 0.1ms, which is more than a factor of 10 faster than LCDs. For a simple test of Motion Blur we photographed a DisplayMate Test Pattern moving at a very fast 1352 pixels per second using a Nikon DSLR camera with a shutter speed of 1/250th second, which is less than the display’s 120 Hz refresh cycle time. Figure 4 has a screen shot for the OLED TV and a similar screen shot for an LCD TV from a 2011 study. Both TVs have a 120 Hz Refresh Rate. On the LCD TV screen shot it is possible to make out latent images from more than 5 prior refresh cycles. The OLED TV screen shot shows a single sharp image. See our LCD Response Time and Motion Blur article for more details.

OLED TV Test Result: The OLED screen shot shows no visible Motion Blur or latent images from any previous refresh cycles, so the Response Time is visually indistinguishable from zero with no visible display based Motion Blur.

 

Figure 4a.  OLED TV Motion Blur Screen Shot

1352 Pixels Per Second Motion 1/250th Sec Photo

Figure 4b.  LCD TV Motion Blur Screen Shot

1352 Pixels Per Second Motion 1/250th Sec Photo

 

Stuck or Dead Pixels

With millions of sub-pixels on the screen, it’s not unusual for displays to have some stuck or dead sub-pixels that remain permanently On or permanently Off. Our particular OLED TV has zero stuck or dead sub-pixels, which is impressive. Playing Sherlock Holmes with test patterns and a magnifier we were able to find two somewhat hyperactive white sub-pixels that were too bright at very dark gray levels but otherwise fine for black or brighter intensities. Under normal viewing conditions they are not visible.

OLED TV Test Result: All sub-pixels are visually indistinguishable from perfect.

 

Screen Saver

One interesting feature of the LG OLED TV is its subtle screen saver. When it detects an image that remains unchanged for over a minute, it begins to slowly decrease the brightness by 10-15% per minute until the Luminance reaches about 75 cd/m2. This can happen as the result of pressing pause on a Blu-ray player or photo slide show, or leaving the web browser on a single page. Once the image changes again (or you click on the remote control) the picture returns back to normal brightness. This reduces display power and any possible screen aging effects.

 

Power Consumption

Because it is an emissive display the power used by the OLED TV depends on the image content. With an entirely black screen the TV uses only about 50 watts of power. As the Average Picture Level APL increases and as the Peak Brightness setting increases the OLED display uses more power. The THX Cinema mode uses the least power because it has the lowest brightness. For an APL of 20%, which is typical for most TV, movie and video content, the TV uses 78 watts in the THX Cinema mode. The Standard and Vivid modes use the most power because they are the brightest Picture modes. For an APL of 20% they use 185 watts. For the highest APLs the maximum power we measured was 215 watts (which is a somewhat less than the 300 watts LG specifies).

 

About the Author

Dr. Raymond Soneira is President of DisplayMate Technologies Corporation of Amherst, New Hampshire, which produces video calibration, evaluation, and diagnostic products for consumers, technicians, and manufacturers. See www.displaymate.com. He is a research scientist with a career that spans physics, computer science, and television system design. Dr. Soneira obtained his Ph.D. in Theoretical Physics from Princeton University, spent 5 years as a Long-Term Member of the world famous Institute for Advanced Study in Princeton, another 5 years as a Principal Investigator in the Computer Systems Research Laboratory at AT&T Bell Laboratories, and has also designed, tested, and installed color television broadcast equipment for the CBS Television Network Engineering and Development Department. He has authored over 35 research articles in scientific journals in physics and computer science, including Scientific American. If you have any comments or questions about the article, you can contact him at dtso.info@displaymate.com.

 

DisplayMate Display Optimization Technology

All displays can be significantly improved using DisplayMate’s advanced scientific analysis and mathematical display modeling and optimization of the display hardware, factory calibration, and driver parameters. We help manufacturers with expert display procurement and quality control so they don’t make mistakes similar to those that are exposed in our Display Technology Shoot-Out series. We can also improve the performance of any specified set of display parameters. This article is a lite version of our intensive scientific analysis – before the benefits of our DisplayMate Display Optimization Technology, which can correct or improve all of these issues. If you are a display or product manufacturer and want to significantly improve display performance for a competitive advantage then Contact DisplayMate Technologies.

 

About DisplayMate Technologies

DisplayMate Technologies specializes in proprietary sophisticated scientific display calibration and mathematical display optimization to deliver unsurpassed objective performance, picture quality and accuracy for all types of displays including video and computer monitors, projectors, HDTVs, mobile displays such as smartphones and tablets, and all display technologies including LCD, OLED, 3D, LED, LCoS, Plasma, DLP and CRT. This article is a lite version of our intensive scientific analysis of all types of displays – before the benefits of our advanced mathematical DisplayMate Display Optimization Technology, which can correct or improve many of the display deficiencies. We offer DisplayMate display calibration software for consumers and advanced DisplayMate display diagnostic and calibration software for technicians and test labs.

 

For manufacturers we offer Consulting Services that include advanced Lab testing and evaluations, confidential Shoot-Outs with competing products, calibration and optimization for displays, cameras and their User Interface, plus on-site and factory visits. See our world renown Display Technology Shoot-Out public article series for an introduction and preview. DisplayMate’s advanced scientific optimizations can make lower cost panels look as good or better than more expensive higher performance displays. For more information on our technology see the Summary description of our Adaptive Variable Metric Display Optimizer AVDO. If you are a display or product manufacturer and want to turn your display into a spectacular one to surpass your competition then Contact DisplayMate Technologies to learn more.

 

Article Links:  Display Technology Shoot-Out Article Series Overview and Home Page

Article Links:  Mobile Display Shoot-Out Article Series Overview and Home Page

 

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