High TV Picture Quality in Real World Ambient Lighting

With the Samsung 65Q9 QLED TV

 

Dr. Raymond M. Soneira

President, DisplayMate Technologies Corporation

 

Copyright © 1990-2017 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

All displays from TVs to Smartphones deliver their best picture quality and their most accurate colors in the dark, and essentially all published product specifications that you see are for absolute darkness.

 

But almost no one watches their TV or any other display in complete darkness. When the level of ambient lighting increases the on-screen colors and picture quality begin to progressively degrade as the ambient light falling on the screen increasingly washes out the picture, an effect that everyone is very familiar with.

 

However, there are substantial differences in how well different displays and TVs actually perform in ambient light... In this article we are going to measure and demonstrate how the actual on-screen colors change in ambient light for different TVs and display performance settings, and then show how to significantly improve display performance in real world ambient light viewing conditions. The main factors, as we explain below, are high screen Brightness, low screen Reflectance, and an extra Wide Color Gamut together with advanced Color Management. We will demonstrate in turn how each of these factors affects on-screen color in ambient light.

 

For this article we are using Samsung’s flagship 65Q9 QLED TV, which has a 65 inch QLED LCD with Quantum Dots that produces a record Maximum Brightness (Luminance) of 930 nits (for Standard Dynamic Range SDR picture content with high APL Average Picture Levels), a record low Screen Reflectance of 1.2%, and a record 4K Ultra HD TV Wide Color Gamut of 108% DCI-P3. As a result it has by far the best high ambient light performance of any display that we have ever tested, so it is ideal for demonstrating all of the issues and factors involved.

                                                                                                                                                                                          

For comparison and to put everything into proper perspective we will also test and measure several other settings of the Samsung 65Q9 TV for lower Brightness and for an equivalent higher Screen Reflectance, which are typical for most TV and Smartphone displays. For each setting and variation we will measure and compare the on-screen colors for 5 levels of ambient lighting from 0 lux up through 2,000 lux with spectroradiometer measurements. This will provide major insights into how the different display performance factors and variations affect the picture quality and colors in ambient lighting.

 

Finally, we will show how to further improve display performance in ambient light by using even Wider Native Color Gamuts with Dynamic Color Management in the future. A major advantage for using this advanced technology rather than the current brute force method of just increasing the Picture Brightness in ambient light is that it can produce the same vibrant on-screen colors in ambient light with 75 percent less display power up through 2,000 lux, which is very important for TV energy efficiency, and also very important for Smartphones because they depend on limited battery power.

 

 

Article Overview

This article has the following major sections:

 

Typical Real World Ambient Light Viewing Conditions for TVs

Factors Affecting Display Performance in Ambient Light

TV Testing in Ambient Light

 

Ambient Light Performance for a Typical LCD TV

Ambient Light Performance for the Samsung 65Q9 TV set for Maximum Brightness

Ambient Light Performance for the Samsung 65Q9 TV set for Movie Mode Viewing

Ambient Light Performance using Dynamic Color Management

 

Conclusions for Real World Ambient Light TV Viewing

Next Generation Display Performance in Ambient Light with Dynamic Color Management

 

 

Typical Real World Ambient Light Viewing Conditions for TVs

The level of ambient light is scientifically called Illuminance, and is measured in units of lux, which is a lumen per square meter. If you are a photographer you may have a light meter that is calibrated in lux. For our measurements we use a laboratory Konica Minolta Illuminance meter. Below is a discussion of the lux levels that you are likely to encounter for indoor TV viewing.

 

Movie theaters are very dark with close to 0 lux ambient light falling on the screen – they only have a small amount of controlled lighting aimed at the floor for safety. If you have a dedicated home theater with carefully controlled low level ambient lighting then the effects we discuss here may be relatively small, but if you watch TV during the day in a room with windows, or at night with the room lights on, then our ambient light results will be relevant for your TV watching. Plus on weekends there are always lots of daytime TV sports programs that include colorful uniforms, deep green grass and foliage, and colorful scenery that shouldn’t appear washed out in daytime ambient light.

 

For rooms with small or no windows:

·  Home theaters are often set to under 50 lux.

·  TV nighttime viewing in a typical darkened living room is likely to be in the neighborhood of 125 lux.

·  Not counting outdoor daylight and sunlight coming through the windows, residential indoor lighting is typically around 300 lux, but for reading and task lighting it can climb to 500 lux or more.

·  Discrete light sources like lamps around the room may produce extra bright reflections visible on the screen.

 

For rooms with windows there is a tremendous range of ambient lighting:

·  All windows will deliver indirect Daylight during the day, and in some cases from outdoor lighting at night.

·  Northern exposure windows will get no direct sunlight.

·  Southern exposure windows may get sunlight for most of the day, but due to the incoming angle, direct sunlight generally does not stray too far into the room.

·  Eastern and western exposure windows often result in direct sunlight in the early morning or late afternoon that can stream all the way across the room.

·  TVs with screens facing windows may produce strong reflections on the screen.

·  TVs placed near or in front of windows may be hard to see due to the eye’s sensitivity accommodation to bright light.

 

Sunlight and Daylight indoors:

·  Ordinary diffuse Daylight from a clear blue sky can be 10,000 lux or more outdoors, and will come through the windows from all directions.

·  Outdoor overhead direct sunlight is around 120,000 lux for the US, which is also reflected by all outdoor objects to produce additional diffuse ambient lighting.

·  Direct sunlight streaming through windows can often be 20,000 lux or more.

·  Direct sunlight coming inside will bounce diffusely off the walls, floor, and room contents, adding to the overall level of room ambient lighting.

·  Keep TVs far away from any wall or floor area that can get direct sunlight.

 

An Example: in my living room, which has several northern and western exposure windows, the TV is set diagonally so that it doesn’t face any windows. On an overcast day the room ambient light level is around 300 lux. On a sunny day during the middle of the day the room ambient light level can reach 1,000 lux, and in the late afternoon over 2,000 lux as the sunlight streams across the room (but doesn’t hit the screen).

 

Obviously, your results will vary depending on your own TV viewing conditions and room layout, but we will perform our tests and measurements for five ambient light levels: 0 lux, 125 lux, 500 lux, 1,000 lux, and 2,000 lux.

 

 

Factors Affecting Display Performance in Ambient Light

Below are the primary factors that affect display performance in ambient light:

 

·  Increasing the Picture Brightness:

Increasing the Picture Brightness is the best known method for improving picture quality in ambient light that everyone knows about, which is available to varying degrees for almost all displays, although the Maximum Brightness varies significantly among displays. But don’t permanently set the Picture Brightness all the way up to its Maximum, because that can lead to eye fatigue and headaches, as well as requiring significantly more power for the display. High Picture Brightness is only needed in high ambient lighting, so an Automatic Brightness Control is generally provided to help set the appropriate level, but it also needs to be viewer adjustable because the optimum screen brightness depends on both the overall viewing conditions and individual personal preferences.

 

·  Decreasing the 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.

 

Since the picture becomes washed out as the result of ambient light reflecting off the screen, one way to improve both the picture quality and color is by lowering the percentage of reflected light, which is called the Screen Reflectance – the lower the better. But doing this is both technically challenging and expensive, particularly for large screen TVs. The Screen Reflectance from a TV or Smartphone display that uses untreated cover glass is typically around 5%, but can go up to 10% or more if the display optics includes any internal air gaps. Note that matte screen finishes, which are designed to diffuse the reflections to try to make them less noticeable, none-the-less actually increase the total Screen Reflectance, so there are a number of tradeoffs involved.

 

Optical Anti-Reflection coatings and treatments are frequently used in lenses for high-end cameras, but they are much less common for displays, particularly TVs. The lower the Screen Reflectance the better. In fact, decreasing the Screen Reflectance by 50 percent then doubles the effective Contrast Ratio in ambient light, so it is quantitatively equivalent to doubling the display Brightness (Luminance), and provides a major performance advantage in ambient light.

 

·  Enlarging the Color Gamut:

Since ambient light washes out the visible on-screen colors, a higher-tech method to improve the picture quality in ambient light is to start with a larger Color Gamut, which provides higher color saturation that can offset and compensate for the loss of picture color in ambient light. But the increased Gamut has to be carefully adjusted according to the current level of ambient light so that the picture colors come out correct, which is accomplished with Dynamic Color Management, which we discuss below.

 

The new wide Color Gamuts in 4K Ultra HD TVs can already be used to provide the needed extra color saturation boost for the 2K Full HD picture content, which has a smaller Color Gamut but still accounts for most of the current consumer TV content. We’ll demonstrate this below...

 

Even larger Color Gamuts are now becoming available using Quantum Dots that can be used in QLED and LCD TVs to expand this color enhancement technology to improve 4K Ultra HD picture content in ambient light, and also extend its range to even higher levels of ambient light.

 

As we show below, a major bonus for using a larger Color Gamut in ambient light is that it requires considerably less display power than the current brute force method of just increasing the Screen Brightness. This technology can produce the same vibrant on-screen colors in ambient light with 75 percent less display power up through 2,000 lux, which is very important for TV energy efficiency, and also very important for Smartphones because they depend on limited battery power.

 

 

TV Testing in Ambient Light

In order to accurately measure display performance in ambient light we use a large Integrating Hemisphere placed over the TV that uniformly illuminates the screen with light from all directions to create a uniform isotropic light distribution over the screen. A small opening near the top of the Hemisphere is used to make the spectroradiometer screen measurements in ambient light.

 

·  Ambient Light Variations:

The intensity of the ambient light in the Hemisphere is adjustable and we accurately set each level for the tests by using a laboratory Konica Minolta Illuminance probe placed inside the Hemisphere. We selected five different ambient light levels as described above for: 0 lux, 125 lux, 500 lux, 1,000 lux, and 2,000 lux.

 

·  Color Gamut Variations:

We measure the variation in the on-screen Color Gamuts at each ambient light lux level for both the 2K Full HD Color Gamut of sRGB/Rec.709, and the 4K Ultra HD Native Color Gamut of the Samsung 65Q9 TV, which is 108% of DCI-P3. The color measurements are all shown on a CIE 1976 Uniform Chromaticity Diagram. See the Accurately Colorized CIE Diagram below and this article for an in-depth discussion on interpreting the Color Gamuts.

 

·  Screen Brightness Variations:

The Screen Brightness (Luminance) measurements were made for three TV Brightness levels: 240 nits (Movie Mode), 350 nits (Typical LCD TV), and 930 nits (Maximum SDR Brightness). They show how the TV performance in ambient light varies with Luminance.

 

·  Screen Reflectance Variations:

We measured the Screen Reflectance of the Samsung 65Q9 TV screen to be 1.2% using the Integrating Hemisphere and a spectroradiometer. This very low Screen Reflectance is due to the use of an Anti-Reflection treatment. In order to measure the performance for a Typical LCD TV that lacks an Anti-Reflection treatment resulting in 5.0% Screen Reflectance, which is a factor of 4.2 greater than the 1.2% measured on the Samsung 65Q9 TV, we rescaled the ambient light and Luminance to provide an exact quantitatively equivalent measurement result.

 

Accurately Colorized CIE Diagram for the Full HD and Ultra HD Color Gamuts

When the Color Gamut shrinks in ambient light as shown in Figures 1-4 below, the corresponding colors shown in the Colorized CIE Diagram above are shifted inward and appear with lower color saturation on-screen. Refer to this article on Color Gamuts for more information.

 

 

Ambient Light Performance for a Typical Generic LCD TV

Typical Generic LCD TVs have a Peak Brightness (Luminance) of 350 nits, and a Screen Reflectance of 5% (as the result of not using an Anti-Reflection treatment) . While the Screen Brightness seems nice and high, the 5% Screen Reflectance noticeably washes out the picture color in moderate ambient light as shown below.

 

Below is the variation of the Color Gamut in Ambient Light from 0 lux up through 2,000 lux for both the 2K Full HD Color Gamut of sRGB/Rec.709 and the 4K Ultra HD Color Gamut of DCI-P3.

 

 

For low ambient lighting, the Typical LCD TV still provides good color up through 125 lux, but above that there is a significant decrease in color saturation, particularly for 2K Full HD picture content. On the other hand, for 4K Ultra HD picture content, the colors start out over-saturated at 108% of the Gamut at 0 lux, so the colors remain fairly good up until 500 lux, but then rapidly decrease above that.

 

 

Ambient Light Performance for the Samsung 65Q9 TV set for Maximum Brightness

The Samsung 65Q9 TV provides the best TV high ambient light viewing with its record high SDR Peak Brightness (Luminance) of 930 nits and a record low Screen Reflectance of 1.2%, which provides the best ambient light performance for current TVs.

 

Below is the variation of the Color Gamut in Ambient Light from 0 lux up through 2,000 lux for both the 2K Full HD Color Gamut of sRGB/Rec.709 and the 4K Ultra HD Color Gamut of DCI-P3.

 

 

The Samsung 65Q9 TV set for its Maximum SDR Brightness of 930 nits provides excellent color in high ambient light, substantially better than the Typical LCD TV examined above (in Figure 1 and Table 1), with only a barely noticeable decrease in color up through 2,000 lux for 2K Full HD picture content. For 4K Ultra HD picture content, the colors start out over-saturated at 108% of the Gamut at 0 lux, and continue to deliver strong color up through 2,000 lux. High Dynamic Range HDR picture content is even brighter at over 2,000 nits, so the HDR picture content shows even smaller color variations in ambient light.

 

 

Ambient Light Performance for the Samsung 65Q9 TV set for Movie Mode Viewing

In order to study the effects of lower Screen Brightness in ambient light, we also set the Samsung 65Q9 TV to a much lower Screen Brightness (Luminance) of 240 nits, which is 1/4 of the Maximum 930 nits. This level is often used for watching movie content on many TVs, which generally provide an appropriately named Movie mode or Cinema mode.

 

Below is the variation of the Color Gamut in Ambient Light from 0 lux up through 2,000 lux for both the 2K Full HD Color Gamut of sRGB/Rec.709 and the 4K Ultra HD Color Gamut of DCI-P3.

 

 

The most interesting result here is that the Samsung 65Q9 TV with just 240 nits (Table 3) performs significantly better in ambient light than the Typical LCD TV with 350 nits (Table 1) because the Samsung 65Q9 TV has a very low Screen Reflectance of 1.2%, while most LCD TVs typically have a screen Reflectance of 5.0% (or more). That is 32% higher color saturation on the Samsung 65Q9 TV using 31% lower Screen Brightness.

 

 

Ambient Light Performance using Dynamic Color Management

Since ambient light washes out the visible on-screen colors, a higher-tech method to improve the picture quality in ambient light is to start with a larger Color Gamut, which provides higher color saturation that can offset and compensate for the loss of picture color in ambient light. However, the increased Gamut has to be carefully adjusted according to the current level of ambient light so that the colors come out correct on-screen. This Dynamic Color Gamut is produced by using Dynamic Color Management, which adjusts (reduces) the display’s Wider Native Color Gamut so that the on-screen Color Gamut for picture content is accurately produced for the current ambient light level.

 

With this technology, an Ambient Light Sensor on the TV measures the current ambient light level and then adjusts the Color Gamut so that the picture colors come out correct on-screen. That will only work up through a maximum ambient light level that reaches the TV’s full Native Color Gamut, which then remains fixed for higher ambient light levels.

 

Below is the variation of the Color Gamut in Ambient Light from 0 lux up through 2,000 lux for the 2K Full HD Color Gamut of sRGB/Rec.709 using Dynamic Color Management of the Native Color Gamut, which is 108% of DCI-P3.

 

 

The most interesting and impressive result here is that the Samsung 65Q9 TV with just 240 nits and Dynamic Color Gamut (Table 4) performs almost as well as with 930 nits and a fixed Color Gamut (Table 2) up through 2,000 lux ambient light, which is particularly significant and important because the display power needed for 240 nits is only 1/4 of the display power for 930 nits, which we examine further below.

 

 

Conclusions for Real World Ambient Light TV Viewing

Almost no one watches their TV or any other display in complete darkness. When the level of ambient lighting increases the on-screen colors and picture quality begin to progressively degrade as the ambient light falling on the screen increasingly washes out the picture, an effect that everyone is very familiar with.

 

In this article we have demonstrated with detailed measurements that there are substantial differences in how well different displays and TVs actually perform in ambient light. The main factors are high Screen Brightness, low Screen Reflectance, and a native Wide Color Gamut for the TV that can be Dynamically adjusted based on the current measured ambient light level.

 

Table 5 below summarizes the on-screen color performance results in ambient light for 2K Full HD picture content. Comparable results are listed for 4K Ultra HD picture content in Tables 1-3 above.

 

Table 5.  2K Full HD Performance Summary in Ambient Light

Values below 90% are marked in Red

 

·  For Low Ambient Light levels up to 125 lux all of the TVs and display settings perform well, delivering good color, including the Typical LCD with 350 nits and 5.0% Screen Reflectance.

 

·  But for viewing in typical real world ambient light levels above 125 lux, Low Screen Reflectance plays a key role in providing high picture quality and color in ambient light. The lower the Screen Reflectance the better the picture colors hold up in increasing ambient light.

 

·  The Samsung 65Q9 TV has the lowest Screen Reflectance that we have ever measured (with a tie at 1.2%), providing a major advantage in viewing TV in ambient light. As a result, the Samsung 65Q9 TV with just 240 nits performs significantly better in ambient light than the Typical LCD TV with 350 nits and 5.0% Screen Reflectance.

 

·  Using Higher Picture Brightness is the best known method for improving picture quality in ambient light that everyone knows about, which is available to varying degrees for almost all displays, although the Maximum Brightness varies significantly among displays. The higher the Picture Brightness the better the colors hold up in increasing ambient light.

 

·  The Samsung 65Q9 TV has the highest Maximum Brightness (930 nits) that we have ever measured for SDR Standard Dynamic Range picture content. High Dynamic Range HDR content is even brighter at over 2,000 nits, so the HDR colors hold up even better in ambient light.

 

·  The Samsung 65Q9 TV has a record 4K Ultra HD TV Wide Color Gamut of 108% DCI-P3, which helps to offset the loss of color in high ambient light.

 

As a result of all the above, the Samsung 65Q9 QLED TV delivers the best TV display performance in real world ambient light viewing conditions, which includes all other LCD and OLED technologies.

 

The next step will be using Wider Native Color Gamuts together with Dynamic Color Management, which we discuss below...

 

 

Next Generation Display Performance in Ambient Light with Dynamic Color Management

The above performance results for on-screen picture color in ambient light apply to all displays from TVs to Smartphones... and they can all be further improved significantly... while also providing much higher display power efficiency...

 

Since ambient light washes out the on-screen colors, the first step is to enlarge the Native Color Gamut of the display as much as possible. Quantum Dots, which is the technology used in the Samsung 65Q9 TV, can now further expand the Native Color Gamut very efficiently. Note that in Figures 1 to 4 the Green Primary does not shift much with ambient light, while the Red and Blue Primaries shift the most. The Blue Primary is produced directly with standard Blue LEDs that are used with Quantum Dots, so then Red is the key Primary Color to extend using Quantum Dots. The deeper and more saturated the Red Primary is the better, and the more it will be able to compensate for the loss of color in high ambient light. With a Wider Native Color Gamut the same method described above for 2K Full HD will then accomplish this for the wider 4K Ultra HD DCI-P3 picture content.

 

All TVs and Smartphones currently use fixed Static Color Management to produce their specified fixed sRGB/Rec.709 and DCI-P3 Color Gamuts from the display’s own fixed Native Color Gamut. Since these are fixed at the factory, they do not change with the level of ambient light. That would result in over-saturated colors in low ambient light.

 

The necessary new crucial step is to allow the Color Management parameters to change real-time as needed, which is called Dynamic Color Management. By using Dynamic Color Management the on-screen colors are adjusted based on the current ambient light level measured by the TV or Smartphone Ambient Light Sensor, so that the viewer sees the desired 100% Color Gamut on-screen up through the highest ambient light level that it can compensate for – above that level the maximum Native Color Gamut remains fixed. Even better performance will result when implementing 3D Color Management that also varies with the intensity levels within the picture content.

 

Significantly Lower Display Power in Ambient Light

A major bonus for using Wider Color Gamuts in ambient light rather than using the brute force method of just increasing the Picture Brightness is that as shown in Table 5 above, the Samsung 65Q9 TV with a Dynamic Gamut can produce the same vibrant on-screen colors in ambient light with just 240 nits compared to 930 nits with a Fixed Gamut. Since display power is proportional to the current Screen Brightness setting, the display power is reduced by 75 percent up through 2,000 lux ambient light by using a Dynamic Gamut produced by Dynamic Color Management. This is very important for TV energy efficiency, and also very important for Smartphones because they depend on limited battery power.

 

In this article we have examined how to improve on-screen color and Color Contrast in ambient light by using Dynamic Color Gamuts. Ambient light also reduces the Intensity Contrast that can be similarly improved by using Dynamic Intensity Scales, which we will cover in a future article. Follow DisplayMate on Twitter to learn about these developments and our upcoming display technology coverage.

 

 

About the Author

Dr. Raymond Soneira is President of DisplayMate Technologies Corporation of Amherst, New Hampshire, which produces display 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.

 

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Article Links:  Display Color Gamuts Shoot-Out NTSC to Rec.2020

Article Links:  Mobile Displays in High Ambient Light

 

 

Copyright © 1990-2017 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