Motorola Droid LCD Display Shoot-Out

 

Dr. Raymond M. Soneira

President, DisplayMate Technologies Corporation

 

Copyright © 1990-2010 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

 

 

Series Overview                                                                                          This is part of a comprehensive article series with in-depth measurements and analysis for the OLED and LCD displays in the Google Nexus One, the Apple iPhone 3GS, the Motorola Droid, the Samsung Galaxy S, and the Apple iPhone 4. We will show you the good, the bad, and also the ugly unfinished rough edges and problems lurking below the surface of each of these displays and display technologies, and then demonstrate how the displays can be improved by using images that have been mathematically processed to correct color and imaging errors on each smartphone so you can compare them to the originals. The series begins with the Google Nexus One and Apple iPhone 3GS. It then continues with higher performance “Super” displays in the Motorola Droid, the Samsung Galaxy S, and the Apple iPhone 4. Finally, there is a five way Smartphone "Super" LCD-OLED Display Technology Shoot-Out that compares all of the units simultaneously.         Introduction A key element in the success of all smartphones and mobile devices is the quality and performance of their display. There have been lots of articles comparing various smartphone LCD and OLED displays and technologies, but almost all simply deliver imprecise off-the-cuff remarks like “the display is gorgeous” with very little in the way of serious attempts at objective or accurate display performance evaluations and comparisons – and many just restate manufacturer claims and provide inaccurate information, performance evaluations and conclusions. This article objectively evaluates the display performance of the Motorola Droid IPS LCD display based on extensive scientific lab measurements together with extensive side-by-side visual tests.   The Motorola Droid has a high-performance In Plane Switching IPS LCD display with a White LED backlight. The screen is 3.7 inches diagonally and has a high-resolution high-density 854x480 pixel display with a screen Aspect Ratio of 1.78, which is identical to standard 16:9 widescreen displays, such as HDTVs, which have an Aspect Ratio of 1.78.   Both the Motorola Droid and Nexus One use the Google Android OS. The Nexus One was tested with version 2.1 and the Motorola Droid with version 2.0.1. We found so many image and picture quality problems and implementation issues with the display on the Nexus One that it will be especially interesting to see whether the Motorola Droid, which has the same Android OS, suffers from the same problems and issues, or whether Motorola did a better job of engineering the display hardware, firmware and software than Google and HTC.

 

Important Note for the Android OS 2.1 Upgrade

The tests for this article were performed using the original 2.0 Android OS for the Motorola Droid. Afterwards, when the Droid was upgraded to version 2.1, the Gallery (the principal image viewer for the phone) surprisingly downgraded to 16-bit color from its original full 24-bit color in version 2.0. Fortunately, version 2.1 of the Android Browser on the Droid still delivers full 24-bit color. Image Scaling for the Gallery (which processes images so they fit the native resolution of the display) went from Excellent in version 2.0 to Poor in version 2.1, the same as for the Browser (both versions). As a result the beautiful screen shots for the Droid in Figure 1 below now look exactly like those for the Google Nexus One on the left. Overall, the Droid still delivers substantially better picture quality and accuracy than the Nexus One. Presumably these errors, which affect both the Droid and the Nexus One will be fixed in a future software upgrade, so the Droid will at some point return to its original excellent 24-bit color and scaling. The quality of the 24-bit color and scaling for the Nexus One remains to be seen… Google acknowledges these problems for all 2.1 Android phones including the Nexus One and Motorola Droid. The next major release of the Android OS will fix these issues and provide full 24-bit color and improved scaling. Click Here to read the Google and Cooliris statements commenting on our results.

 

FIGURE 1

Figure 1.  Revealing Screen Shots for the Google Nexus One and Motorola Droid.

Figure 1.  Revealing Screen Shots for the Google Nexus One and Motorola Droid.

The test patterns are 24-bit bmp at the native resolution of each display.

 

Results and Conclusions

The display was evaluated by downloading 24-bit native resolution 854x480 test patterns and 24-bit HD resolution test photos to the phone. Note that we are testing and evaluating the display on the Droid with whatever hardware, firmware, OS and software are provided by Motorola.

 

Color Depth and Granularity:  Excellent Artifact Free 24-bit Color

The Droid provides full on-screen 24-bit color, which has 256 possible intensity levels for each of the Red, Green and Blue sub-pixels that are used to mix and produce all of the on-screen image colors. It’s the same as what is found on most monitors and HDTVs. When done properly, as on the Droid, it produces a nice color and intensity scale with few visible artifacts. Figure 1 shows the smooth intensity scale for both a photograph and test pattern that are visibly free of artifacts on the Droid.

 

Display Image Quality, Colors and Artifacts:  Excellent

The image and picture quality on the Droid is excellent across the board, including text, icons, and menu graphics. In the important category of images, pictures and photographs from external sources, whether they be from digital cameras or web content, are rendered quite well. The calibration is very good and the images and photos are rendered relatively artifact free, including the critical rescaling function that is needed to fit images and photos onto the native 854x480 resolution of the display. The image and picture quality on the Droid is actually better than in most computer monitors and HDTVs. However, there is a problem with rescaling in the Android Browser on the Droid, which exhibits the same artifacts as the Nexus One, and will presumably be fixed in the future.

 

The Measurements with Explanations and Interpretations:

The Measurements section below has details of all of the lab measurements and tests with lots of additional background information and explanations including the display’s Maximum Brightness and Peak Luminance, Black Brightness, Contrast Ratio, Screen Reflectance, Bright Ambient Light Contrast Rating, Dynamic Color and Contrast, Color Temperature and White Chromaticity, Color Gamut, Intensity Scale and Gamma, the variation of Brightness, Contrast Ratio and Color Shift with Viewing Angle, the Power Consumption and Light Spectrum of the display.

 

The Viewing Tests:  Excellent

We compared the Motorola Droid side-by-side to a calibrated Professional Sony High Definition Studio Monitor using a large set of DisplayMate Calibration and Test Photographs. All of the photos on the Droid were an excellent match, including faces and well known objects such as fruits, vegetables, flowers, grass, even a Coca-Cola can. The image and picture quality on the Droid is actually better than in most computer monitors and HDTVs. This is the result of an excellent factory calibration of the Color Gamut and Intensity Scales.

 

Factory Calibration and Quality Control:  Very Good

The overall factory calibration and quality control for the Motorola Droid display are very good. The accuracy of the white point and color and gray-scale tracking are all very good, which means that the Red, Green and Blue primaries have been carefully calibrated and balanced. The images are relatively free of objectionable artifacts.

 

Suggestions for Motorola:

Keep up the good work… To make your displays even better follow the detailed comments and recommendations above and in greater detail below. Also ask Google to fix the poor image rescaling and its 16-bit implementation in the Browser and possibly other Android OS applications.

 

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. If you are a 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.

 

Motorola Droid Conclusion:  Excellent Mobile Display wins Best Mobile Picture Quality Award

The Motorola Droid is an excellent mobile display with just a few comparatively minor shortcomings. In terms of image and picture quality it comes closer to a high quality computer monitor or HDTV than any other mobile display we have tested – all the more impressive because mobile displays operate under challenging size, power and cost constraints. In fact, the image and picture quality and accuracy on the Droid is actually better than in most computer monitors and HDTVs (but smaller, of course). The screen is very bright and very sharp, has excellent color and gray scale accuracy, and has very good Contrast and readability under both dim and bright ambient light. For these reasons we have awarded the Motorola Droid the Best Mobile Picture Quality Award in the DisplayMate Best Video Hardware Guide.

 

 

The Measurements with Explanations and Interpretations

This section explains all of the measurements incorporated in the article. The display was evaluated by downloading 24-bit native resolution 854x480 test patterns and 24-bit HD resolution test photos to the Motorola Droid. Note that we are testing and evaluating the display on the Droid with whatever hardware, firmware, OS and software are provided by Motorola. All measurements were made using DisplayMate Multimedia Edition for Mobile Displays to generate the analytical test patterns together with a Konica Minolta CS-200 ChromaMeter, which is a Spectroradiometer. All measurements were made in a perfectly dark lab to avoid light contamination. All devices were tested with their Backlight set for maximum brightness with the Automatic Brightness light sensor control turned off, and running on their AC power adapter with a fully charged battery, so that the battery performance and state was not a factor in the results. For further in-depth discussions and explanations of the tests, measurements, and their interpretation refer to earlier articles in the DisplayMate Multimedia Display Technology Shoot-Out article series and the DisplayMate Mobile Display Shoot-Out article series.

 

Konica Minolta CS-200

 

1.  Peak Brightness:  449 cd/m²  –  Excellent brightness for a Mobile Display

This is the maximum brightness that the display can produce, called the Peak White Luminance. 449 cd/m² is about as bright as you’ll find on any current mobile display. It’s fine for just about everything except direct sunlight, although it may be too bright for comfortable viewing under dim ambient lighting. If you find that to be the case, turn on the Droid’s Automatic Brightness, which uses a light sensor to adjust the Peak Brightness settings. Since that can be used to decrease the power used by the backlight it will also increase the battery run time.

 

2.  Black Level Brightness:  0.165 cd/m²  –  Good for a Mobile Display

The Black Level is the closest approximation to true black that the display can produce. Almost all displays wind up producing a visible dark gray on-screen instead of true black. This is a major problem for LCDs. The glow reduces image contrast and screen readability and can be distracting or even annoying in dark environments. It ruins the dark end of the display’s intensity/gray scale and washes out colors in the image. But note that in bright ambient lighting the Black Level is irrelevant because reflections off the screen dominate the screen background brightness. The Droid’s value of 0.165 cd/m² is very dark for a mobile display in typical ambient lighting. Note that if you decrease the screen Brightness with the (Backlight) Brightness Control, the Black Brightness will also decrease proportionally by the same amount, so in dimmer ambient lighting the Black Brightness can be reduced significantly if desired.

 

3.  Contrast Ratio  –  Only Relevant for Low Ambient Light:  1,436  –  Good for Mobile  –  Dynamic Contrast is 2,721

The Contrast Ratio is a measure of the full range of brightness that the display is capable of producing. It is the ratio of Peak Brightness to Black Level Brightness. The larger the Contrast Ratio the better, but it is only relevant for low ambient lighting because reflections off the screen dominate the display’s Black Level in bright ambient lighting. The very best LCDs now have (true) Contrast Ratios of 1,500 to 2,000 so the 1,436 value for the Droid is very impressive in a mobile device. Don’t confuse the true Contrast Ratio with the tremendously inflated values that are published by many manufacturers. Because the Droid uses Dynamic Contrast (see below) the Contrast Ratio from the brightness values in 1 and 2 above is a Dynamic Contrast Ratio, and it’s 2,721. The static or true Contrast Ratio for the Droid is 1,436, which is measured at low APL where the Dynamic Contrast has a constant value (see below).

 

4.  Screen Reflectance of Ambient Light:  12.1 Percent  –  Average

The often overlooked Screen Reflectance is actually the most important parameter for a mobile display, even more important than Peak Brightness. The screen reflects a certain percentage of the surrounding ambient light, which adds to the screen background, washes out the image, and makes it harder to see what is on the screen. In high ambient lighting the Screen Reflectance can significantly reduce the visibility and readability of screen content. The lower the Screen Reflectance the better. The value for the Droid of 12.1 percent is in the middle of the range of values we’ve measured for mobile devices. Lowering the Screen Reflectance increases the cost of a display, but it’s the easiest and best way to improve screen readability under bright ambient light. The Screen Reflectance measurements were done in accordance with VESA FPDM 308-1, Reflectance with Diffuse Illumination, using an integrating hemispherical dome and a calibrated diffuse white reflectance standard.

 

5.  High Ambient Light Contrast Rating:  37  –  Very Good

In the same way that the Contrast Ratio measures the screen contrast under low ambient lighting, the Bright Contrast Rating specifies the relative screen contrast under high ambient lighting. It is the ratio of Peak Brightness to Screen Reflectance. The higher the value the better you’ll be able to see what’s on the screen when you are in a bright location. 37 is relatively high, so the Droid is among the best mobile displays for high ambient lighting. For all mobile devices the High Ambient Light Contrast Rating is much more important than the Contrast Ratio.

 

6.  Dynamic Color and Dynamic Contrast:  Yes  –  But for Reducing Power Consumption

Some displays dynamically adjust the color, gray scale and contrast on every image that is displayed using an internal automatic image processing algorithm. The goal is generally to jazz up and “enhance” the picture by stretching and exaggerating the colors and intensity scale. It is similar to the Vivid mode found in many digital cameras and HDTVs. Since it alters and frequently distorts the image it is better left as an option for people who aren’t concerned with picture accuracy and fidelity. Since the Dynamic modes are generally triggered by changes in Average Picture Level, a very simple test for Dynamic Contrast is to separately measure the brightness of full screen Red, Green and Blue images and then compare them to White, which should equal their sum. If they don’t agree then there is Dynamic Color and Contrast processing. For the Droid, the measured Luminance for Red=53, Green=275 and Blue=19 cd/m². Their sum is 347 cd/m², which is 23 percent lower than the measured value for White, 449 cd/m², so the Droid uses a moderate amount of Dynamic Color and Contrast. In fact, at low APL the peak luminance decreases to 237 cd/m² as a result of dimming the LCD backlight, suggesting that the actual goal is to reduce power consumption, rather than image “enhancement.” Still we recommend that Dynamic processing be an option that the user can turn on and off.

 

7.  Color Temperature and Chromaticity:  6752 degrees Kelvin  –  Very Close to D6500, Excellent

White is not a single color but rather falls within a range that is normally specified by a Color Temperature. For accurate color reproduction of most content, including photographs, images and web content it needs to be set to the industry standard D6500, which is how most professional photo and video content is color balanced. D6500 is the color of natural daylight and is similar to a Black Body at 6500 degrees Kelvin. The Droid’s White Point is actually very close to D6500 – see the White Points in Figure 2 below. The measured CIE Chromaticity Coordinates of the White Point are u’=0.1946 v’=0.4680.

 

8.  Color Gamut:  Excellent Match to the sRGB / Rec.709 Standard

The Color Gamut of a display is the range and set of colors that it can produce. The only way that a display will deliver good color and gray scale accuracy is if it is accurately calibrated to an industry standard specification, which for computers, digital cameras, and HDTVs is sRGB or Rec.709. It’s the standard for most content and necessary for accurate color reproduction. If the Color Gamut is smaller than the standard then the image colors will appear too weak and under-saturated. If the Color Gamut is greater than the standard then the image colors will appear too strong and over-saturated. The important point here is that a Color Gamut larger than the standard is also bad, not better. Wider gamuts will not show you any colors or content that are not in the original images, which are almost always color balanced for the sRGB / Rec.709 standard. Wider color gamuts simply distort and decrease color accuracy and should be avoided, except for some special applications.

 

Figure 2 shows the measured Color Gamut for the Nexus One and the Motorola Droid alongside the Standard sRGB / Rec.709 Color Gamut in a CIE 1976 Uniform Chromaticity Diagram. The dots in the center are the measured White Points for the phones along with the D6500 Standard, which is marked as a white circle. The outermost curve are the pure spectral colors and the diagonal line on the bottom right is the line of purples. A given display can only reproduce the colors that lie inside of the triangle formed by its primary colors. Highly saturated colors seldom occur in nature so the colors that are outside of the standard sRGB / Rec.709 triangle are seldom needed and are unlikely to be noticed or missed in the overwhelming majority of real images. When a camera or display can’t reproduce a given color it simply produces the closest most saturated color that it can.

 

FIGURE 2

Figure 2.  CIE 1976 Uniform Chromaticity Diagram showing the Color Gamut and White Points for the Nexus One and Motorola Droid

 

The Droid produces an excellent match to the standard Color Gamut, which is the black triangle in Figure 2, while the Nexus One has much too large a color Gamut. As a result the Droid produces images with an excellent color balance while the Nexus One produces images that have significantly too much color saturation. This applies to all external content viewed on the displays, including web content, such as images, photos and videos. This was easy to see in the viewing tests where we compared the displays side-by-side to a calibrated Professional Sony High Definition Studio Monitor using a large set of DisplayMate Calibration and Test Photographs. All of the photos on the Droid were an excellent match, including faces and well known objects such as fruits, vegetables, flowers, grass, even a Coca-Cola can, while the Nexus One photos had way too much color, to the point of appearing gaudy.

 

9.  Intensity Scale, Image Contrast and Gamma:  Very Good Match to the Standard

The display’s intensity scale not only controls the contrast within an image but it also controls how the Red, Green and Blue primary colors mix to produce all of the on-screen colors. So if it doesn’t obey the industry standard intensity scale then the colors and intensities will be wrong everywhere on-screen because virtually all professional content and all digital cameras use the sRGB / Rec.709 standard, so it’s necessary for accurate image, picture and color reproduction. The standard intensity scale is not linear but rather follows a mathematical power-law, so it is a straight line on a log-log graph. Its slope is called Gamma, which is 2.2 in the standards. In order to deliver accurate color and intensity scales a display must closely match the standard. Figure 3 shows the measured (Transfer Function) Intensity Scale for the Motorola Droid and Nexus One alongside the industry standard Gamma of 2.2, which is a straight line.

 

FIGURE 3

Figure 3.  Intensity Scale for the Nexus One and Motorola Droid

 

The Droid provides a very good match with respect to the standard intensity scale, which is needed in order to accurately reproduce images and pictures for most content. It’s actually better than most HDTVs and computer monitors. Gamma is the slope of the intensity scale, which should be a constant 2.2 like the straight line in Figure 3. In the central 20 to 80 percent signal range the Gamma for the Droid is 2.24, which is an excellent match to the standard.

 

10.  Brightness Decrease with Viewing Angle:  64 percent Decrease in 30 degrees  –  Bad, Very Large

A major problem with many displays, especially LCDs, is that the image changes with the viewing angle, sometimes dramatically. The Peak Brightness, Black Luminance, Contrast Ratio and color generally change with viewing angle (see below). Some display technologies are much better than others. At a moderate 30 degree viewing angle the Peak Brightness of the Droid fell by 64 percent to 160 cd/m², which is an incredibly large decrease. This behavior is typical for LCDs.

 

11.  Black Level and Contrast Ratio Shift with Viewing Angle:  Bad, Very Large

At a moderate 30 degree viewing angle the Black Level Brightness increased by 88 percent to 0.31 cd/m²,  the Contrast Ratio fell to 280 and the Dynamic Contrast to 516. This behavior is typical for LCDs.

 

12.  Color Shift with Viewing Angle:  Excellent, no Visible Shift

Colors generally shift with viewing angle whenever the brightness shifts with viewing angle because the Red, Green and Blue sub-pixels each shift independently and vary with intensity level. At a moderate 30 degree viewing angle Red shifted the most, by Δ(u’v’) = 0.0020, which is ½ times the Just Noticeable Color Difference. Green also by Δ(u’v’) = 0.0020 and Blue shifted the least by 0.0016. These values are so low that the Motorola Droid shows no visible color shift with angle.

 

13.  RGB Display Power Consumption:  Good, Relatively Low

The power consumed by LCD displays is independent of the brightness and color distribution of the images – it only depends on the Brightness setting of the backlight that illuminates the LCD from behind. Dynamic Contrast and the Ambient Light Sensor both modify the manual user backlight brightness setting. The Automatic Brightness option allows the ambient light sensor on the Motorola Droid to adjust the backlight brightness and power setting as the ambient light changes. This not only improves visual comfort but can also increase the battery run time. We turned off Automatic Brightness for the tests but Dynamic Contrast is fully automatic and cannot be disabled so the power varies with the Average Picture Level, falling to a low as 53 percent of Maximum for the lowest APLs. It is possible to indirectly determine the power used by the display by measuring the AC power used by the Droid with different backlight settings. The average power used when the display is dark in standby mode is used as the baseline and is subtracted from the power measured for the other states.

 

Table 1 lists the Measured Relative Power, the Measured Luminance, and the Relative Luminous Efficiency, which is just the Measured Luminance divided by the Measured Relative Power, and normalized to 1.0 for White, which has the highest total efficiency.

 

Table 1.  Motorola Droid LCD Display Power Consumption

 

 

14.  OLED and LCD Spectra:  Very Interesting

The spectra of an LCD display is just the spectrum of the backlight filtered through the individual Red, Green and Blue sub-pixel filters within the panel. OLEDs are emissive devices so the spectra of the Nexus One is just the sum of the individual Red, Green and Blue OLED spectra, modified slightly by the touchscreen layer and anti-reflection absorption layer through which their light must pass. We thought it would be very useful and interesting to compare the spectra of the Nexus One with the spectra of the Motorola Droid, so we asked Konica Minolta to loan us their flagship CS-2000 Spectroradiometer to perform the measurements. The spectra for White, which is the sum of the Red, Green and Blue primaries is shown in Figure 4 for both the Nexus One and Motorola Droid.

 

FIGURE 4

Figure 4.  RGB Spectra for the Nexus One and Motorola Droid

 

As expected the OLED RGB spectra are relatively narrow because of their high color saturation. The Motorola Droid LCD RGB spectra is a filtered broadband spectrum. The backlight for the Droid is a white LED, which consists of a Blue LED with a yellow phosphor.

 

 

Special Thanks to Jay Catral of Konica Minolta for visiting our Lab and bringing the CS-2000 Spectroradiometer to measure the Spectra and the very dark Black Luminance of the Nexus One. And Special Thanks to Konica Minolta Sensing for loaning us the CS-2000 and sending Jay Catral.

 

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.

 

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.

 

Article Links:  Google Nexus One OLED Display

Article Links:  Samsung Galaxy S Super OLED Display

Article Links:  Apple iPhone 3GS LCD Display

Article Links:  Motorola Droid LCD Display

Article Links:  Apple iPhone 4 LCD Display

 

Article Links:  Smartphone "Super" LCD-OLED Display Technology Shoot-Out

 

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

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

 

 

Copyright © 1990-2010 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