Source: http://gizmodo.com/5888618/display-battle-which-phones-and-tablets-dominate-in-the-sun
Tablet and phone screens are gorgeous these days—as long as you're somewhere with walls and a ceiling. Even then, the sun's violent rays can make reading your slate a pain. So which display wins? We've got answers.
DisplayMate's visual wizard Raymond Soneira put the iPad 2, Kindle Fire, Xoom, Galaxy Tab 10.1, iPhone 4, HTC Desire, Droid X, and Galaxy S through an enormous range of lighting conditions—pitch black to full outdoor sunlight. Unless you're planning on using your iPad on the surface of the sun, these are pretty much the only lighting conditions that matter. Now let's go outside.
Introduction
Tablets and Smartphones are all used under a very wide range of ambient lighting conditions that are frequently much brighter than for other displays – like laptops, desktops, and HDTVs. The screens reflect a considerable amount of the surrounding light, which washes out the images you are trying to see. The differences in display brightness and reflectance between models results in large differences in their screen readability, visibility and picture quality, especially under brighter ambient lighting. We demonstrate those differences visually by photographing them inside a laboratory Integrating Hemisphere using a powerful light source under a wide range of lighting levels.
Other than jacking up the screen Brightness, manufacturers have done very little to improve screen readability and picture quality under high ambient lighting. In fact, the displays on virtually all Tablets and Smartphones are mirrors that are good enough to use for personal grooming even in ordinary indoor ambient lighting. There are many anti-reflection coatings and treatments that can be used to significantly improve this situation together with color and intensity scale management profiles derived from the ambient light sensor. The second big payoff is that the display can then be viewed with a lower Brightness setting, which improves the running time on battery – something all users care about that provides a significant competitive edge.
There is very little information (other than anecdotal) on how Tablet and Smartphone displays perform and degrade under bright ambient lighting. Our Mobile Display Technology Shoot-Out article series measures the percentage of light reflected by each of the tested mobile screens, and our Auto Brightness Display Shoot-Out examines the optimum screen brightness levels needed under varying ambient light levels. In this article we photographically compare the displays on the Apple iPad 2, Amazon Kindle Fire, Motorola Xoom, and Samsung Galaxy Tab 10.1 at 8 ambient light levels from absolute darkness (0 lux) up through almost direct sunlight (40,000 lux). An accompanying article performs the same comparison on 4 Smartphones.
Results Highlights
When viewed and photographed in absolute darkness (0 lux) the Tablets and Smartphones all appear fairly similar, with differences in color saturation as the standout feature. But as the Ambient Lighting gets brighter the light reflected from the screens rises and begins washing out the display's native colors and image intensities, eventually dominating and then overwhelming the entire image on screen as seen in the Screen Photograph sections below and in the accompanying article on Smartphones. As that happens the differences between the Tablet and Smartphone displays become quite noticeable and substantial.
The Screens
The cover glass and additional layers (such as the touch screen and optional screen protector if you use one) that lie over the display panel currently don't get as much attention or respect as they deserve for their considerable impact on picture quality and screen visibility in bright lighting. People primarily think about their impact on scratch resistance, breakage, and fingerprints. The reason they are so important to the image quality is that any external light that is reflected from the screen travels through the top layers twice: once on the way in and then again on the way out after being reflected. So if the layers affect the image characteristics by "x" then the reflected component is affected by x2 (not 2x), which is considerably larger. So any problems or irregularities in the screens are magnified in bright ambient lighting. Consumers should use care in selecting a screen protector, because many increase the screen reflectance considerably, even those that claim to reduce it.
The Best: Apple iPhone 4 and iPad 2 and the Samsung Galaxy S and Tab 10.1
With DisplayMate Contrast Ratings for High Ambient Light of 47 or more the Apple and Samsung displays deliver the best screen visibility and picture quality in bright environments as seen in the Screen Photographs sections below and in the accompanying article on Smartphones. In bright lighting the Apple and Samsung screens are fairly color neutral and do not impart any noticeable color caste, and there were no noticeable image irregularities introduced by the upper screen layers. While the Apple and Samsung models are decidedly the best, both the Lab Contrast Rating measurements and the Screen Photographs show that the Samsung Galaxy models are somewhat better – so Samsung is the declared winner for High Ambient Light performance, but only by a nose…
The Worst: Amazon Kindle Fire, HTC Desire, and the Motorola Xoom and Droid X
With DisplayMate Contrast Ratings for High Ambient Light in the teens, 20s and low 30s the Amazon, HTC, and Motorola displays delivered much worse screen visibility and picture quality in bright environments as seen in the Screen Photographs sections below and in the accompanying article on Smartphones. The HTC Desire came in decidedly last place with by far the poorest performance. In bright lighting the Kindle Fire has a noticeable diagonal crosshatch pattern from the touch screen conductors, and the Droid X has noticeable diagonal banding introduced by variations in bonding the top layers. There is also a noticeable color caste introduced by the upper layers of the screens: the Kindle Fire has a green caste, the Xoom a blue caste, and the Desire and Droid X a cyan caste.
Range of Ambient Lighting
Our eyes have a tremendous dynamic range because everyday we experience a tremendous range of ambient lighting levels from absolute darkness (0 lux) up through direct sunlight (120,000 lux). Tablets and Smartphones, as mobile devices, must be viewed under this incredible range of ambient light. Ambient light levels are measured in lux, which is a Lumen per square meter. Below is a list of representative lux levels. The values and ranges are approximate and can vary based on the situation particulars including location, orientation, time of day, and time of year. The outdoor levels are for sunlight at noon.
Tablets and Smartphones tend to be held at angles that pick up more of the surrounding ambient light than the more vertically oriented screens in laptops, desktops, and HDTVs. On the other hand, for Tablets and Smartphones in many cases you can change your orientation, location, and viewing angle to reduce the amount of light being picked up by the screens.
Lab Screen Photographs and Measurements with Ambient Lighting
In the Screen Photographs sections below we visually compare the Tablet display's visibility and image contrast. There are two sets: The first set shows the 4 Tablets side-by-side for each individual lux level so you can directly compare their relative performance. The second set shows all of the lux levels together for each of the Tablets individually, so you can see how rapidly each Tablet degrades with ambient light.
The screen photographs were all taken inside a large Integrating Hemisphere that uniformly illuminates the screen in all directions with a powerful daylight 6500 Kelvin light source. Missing from the Lab photos are the superimposed images you would see of your face and surrounding objects that are embedded within the screen reflections. The Tablets were all set to their Maximum Brightness and the Ambient Lighting Levels were measured with a Konica Minolta T-10M Illuminance Meter. We used one of our proprietary DisplayMate Ambient Light Test Patterns with 10 scales in 8 colors (including gray/white) each with 25 intensity steps. As the Ambient Light Level increases you will be able to make out fewer and fewer of the intensity steps. The two Reverse Scales make it possible to count the number of invisible or barely visible steps. Tablets with a larger High Ambient Light Contrast Rating will show more of the Intensity Scale at a given lux level. The more steps you can see the better the Tablet display.
Important Note for Viewing All of the Photos:
The photos are all taken with the camera's automatic exposure, which will vary based on the total brightness of the image (display plus reflected light). That's the same way your eyes process all images. The borders between the photos are at true Black. Use them to compare the Black Levels in the photos. All of the photos are taken at the display's maximum brightness setting, which is also its maximum power setting. The visibility of image content will decrease at lower settings. Most Automatic Brightness Controls will significantly lower the display brightness settings below 5,000 lux in order to save power and increase the running time on battery. It's a challenging compromise that all current Automatic Brightness Controls perform poorly…
Lab Screen Photographs with Ambient Lighting for all Tablets Side-by-Side
Comparisons of the Apple iPad 2, Amazon Kindle Fire, Motorola Xoom, and Samsung Galaxy Tab 10.1.
The lux level descriptions are representative. Refer to the Ranges listed in Table 1 above for an overview.
In absolute darkness you will see the best picture quality with the best color, image contrast, and gray scale accuracy that the display can produce. There is no ambient light to wash out the colors, intensities, and image contrast on the display. If you are a purist obsessed with Black Levels and Contrast Ratios this will either be your best or most irritating viewing conditions. Be sure to significantly lower the Brightness setting of the display in order to reduce eye strain. For LCDs, this will also significantly lower the visibility of the annoying Black Levels (they will already be close to zero for OLED displays). All 4 of the tested Tablets have LCD displays. But… the eye's light sensitivity increases in the dark so you will actually notice the Black Levels more when viewing dark images in the dark. At slightly higher Ambient Lighting (below) the Black Levels will become less noticeable – this is referred to as Bias Lighting.
At the moderate indoor ambient light levels the images should appear only slightly degraded from the 0 lux images that are shown above. The images should show very good color, image contrast, and gray scale accuracy. There is not much ambient light to wash out the colors and contrast on the display, but the Screen Reflectance is already larger than each of the display's own Black Level.
At the bright indoor ambient light levels the images appear noticeably degraded from the 0 lux and 300 lux images above. The images should still show satisfactory color, image contrast, and gray scale accuracy. The ambient light is starting to noticeably wash out the colors and image contrast on the display. The images on the iPad and Galaxy Tab are not as washed out as on the Kindle Fire and Xoom due to their larger Contrast Rating for High Ambient Light.
At outdoor lighting in heavy shade ambient light levels the images appear more degraded than the 1,000 lux images above. The ambient light is noticeably washing out the colors and image contrast on the display. The images on the iPad and Galaxy Tab are not as washed out as on the Kindle Fire and Xoom due to their larger Contrast Rating for High Ambient Light.
For moderate overcast sky ambient light levels the images appear significantly degraded from the previous sets. This lux level also corresponds to the shadow cast by a person in direct sunlight that falls on the display screen they are viewing. The images are showing significantly reduced color, image contrast, and gray scale accuracy. The ambient light is significantly washing out the colors and image contrast on the display. The images on the iPad and Galaxy Tab are not as washed out as on the Kindle Fire and Xoom due to their larger Contrast Rating for High Ambient Light.
For moderate outdoor daylight ambient light levels the images appear substantially degraded. The images show large reductions in color, image contrast, and gray scale accuracy. The high ambient light is substantially washing out the colors and image contrast on each display. The images on the iPad and Galaxy Tab are not as washed out as on the Kindle Fire and Xoom due to their larger Contrast Rating for High Ambient Light.
For full daylight not in direct sunlight or indirect indoor sunlight ambient light levels these images are barely visible. The images on the iPad and Galaxy Tab are not as washed out as on the Kindle Fire and Xoom due to their larger Contrast Rating for High Ambient Light.
At the indirect outdoor sunlight ambient light levels these images are almost invisible. The images on the iPad and Galaxy Tab are not as washed out as on the Kindle Fire and Xoom due to their larger Contrast Rating for High Ambient Light.
Lab Screen Photographs with Ambient Lighting for all Smartphones Side-by-Side
Comparisons of the Apple iPhone 4, HTC Desire, Motorola Droid X, and Samsung Galaxy S.
The lux level descriptions are representative. Refer to the Ranges listed in Table 1 above for an overview.
In absolute darkness you will see the best picture quality with the best color, image contrast, and gray scale accuracy that the display can produce. There is no ambient light to wash out the colors, intensities, and image contrast on the display. If you are a purist obsessed with Black Levels and Contrast Ratios this will either be your best or most irritating viewing conditions. Be sure to significantly lower the Brightness setting of the display in order to reduce eye strain. For LCDs, this will also significantly lower the visibility of the annoying Black Levels (they will already be close to zero for OLED displays). The iPhone 4 and Droid X have LCD displays and the HTC Desire and Galaxy S have OLED displays. But… the eye's light sensitivity increases in the dark so you will actually notice the Black Levels more when viewing dark images in the dark. At slightly higher Ambient Lighting (below) the Black Levels will become less noticeable – this is referred to as Bias Lighting.
At the moderate indoor ambient light levels the images should appear only slightly degraded from the 0 lux images that are shown above. The images should show very good color, image contrast, and gray scale accuracy. There is not much ambient light to wash out the colors and contrast on the display, but the Screen Reflectance is already larger than each of the display's own Black Level.
At the bright indoor ambient light levels the images appear noticeably degraded from the 0 lux and 300 lux images above. The images should still show satisfactory color, image contrast, and gray scale accuracy. The ambient light is starting to noticeably wash out the colors and image contrast on the display. The images on the iPhone 4 and Galaxy S are not as washed out as on the HTC Desire and Droid X due to their larger Contrast Rating for High Ambient Light.
At outdoor lighting in heavy shade ambient light levels the images appear more degraded than the 1,000 lux images above. The ambient light is noticeably washing out the colors and image contrast on the display. The images on the iPhone 4 and Galaxy S are not as washed out as on the HTC Desire and Droid X due to their larger Contrast Rating for High Ambient Light.
For moderate overcast sky ambient light levels the images appear significantly degraded from the previous sets. This lux level also corresponds to the shadow cast by a person in direct sunlight that falls on the display screen they are viewing. The images are showing significantly reduced color, image contrast, and gray scale accuracy. The ambient light is significantly washing out the colors and image contrast on the display. The images on the iPhone 4 and Galaxy S are not as washed out as on the HTC Desire and Droid X due to their larger Contrast Rating for High Ambient Light.
For moderate outdoor daylight ambient light levels the images appear substantially degraded. The images show large reductions in color, image contrast, and gray scale accuracy. The high ambient light is substantially washing out the colors and image contrast on each display. The images on the iPhone 4 and Galaxy S are not as washed out as on the HTC Desire and Droid X due to their larger Contrast Rating for High Ambient Light.
For full daylight not in direct sunlight or indirect indoor sunlight ambient light levels these images are barely visible. The images on the iPhone 4 and Galaxy S are not as washed out as on the HTC Desire and Droid X due to their larger Contrast Rating for High Ambient Light.
At the indirect outdoor sunlight ambient light levels these images are almost invisible. The images on the iPhone 4 and Galaxy S are not as washed out as on the HTC Desire and Droid X due to their larger Contrast Rating for High Ambient Light.
This article has been republished with permission from 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.
About DisplayMate Technologies
DisplayMate Technologies specializes in advanced mathematical display technology optimizations and precision analytical scientific display diagnostics and calibrations to deliver outstanding image and picture quality and accuracy – while increasing the effective visual Contrast Ratio of the display and producing a higher calibrated brightness than is achievable with traditional calibration methods. This also decreases display power requirements and increases the battery run time in mobile displays. This article is a lite version of our intensive scientific analysis of smartphone and mobile displays – before the benefits of our advanced mathematical DisplayMate Display Optimization Technology, which can correct or improve many of the deficiencies – including higher calibrated brightness, power efficiency, effective screen contrast, picture quality and color and gray scale accuracy under both bright and dim ambient light, and much more. Our 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 our expertise and technology to turn your display into a spectacular one to surpass your competition then Contact DisplayMate Technologies to learn more.