Smart Watch Display Technology Shoot-Out

Sony SmartWatch 2  –  Samsung Gear 2

Dr. Raymond M. Soneira

President, DisplayMate Technologies Corporation

 

Copyright © 1990-2014 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

The flood gates for the next major smart device revolution are opening. And unless you have been living under a rock you already know that this time it’s a smart watch, a long overdue update to what is essentially 19th century wrist watch technology. There are already a fair number of early players in this new category – in this article we’ll examine how well the displays in two second generation smart watches from two top tier manufacturers perform: the Sony SmartWatch 2, with an LCD display, and the Samsung Gear 2, with an OLED display.

 

Smart watches are the next revolution in tech gadgets because a watch should be able to tell you a lot more than just the time. Plus, smartphones are now so important and doing so much that they need a readily assessable and conveniently viewable assistant to help out with all that’s going on in the smartphone – a smart watch is perfect for this and your wrist is prime coveted real-estate. So if you get lots of text messages, Emails, appointment and App alerts, or even voice calls, then a smart watch will be very useful and helpful. It’s no surprise that most of the major mobile tech players are expected to compete in this new category, including (alphabetically) Apple, Google, LG, Motorola, Qualcomm, Samsung, and Sony.

 

The display is clearly the most important and key component in a smart watch…

And most people will expect a smart watch to have a display with quality comparable to their smartphone:

That turns out to be a major challenge for a number of reasons. First, the screen size is only about 1.5 inches, so the display needs a fairly high resolution in pixels per inch in order to provide sharp and easy to read fine text and graphics. It also needs to produce fairly bright images because watches are often viewed in high ambient light. A larger color gamut is also needed to counteract color washout from ambient light, plus vibrant saturated colors are quite helpful when reading screens with text and graphics information. A major challenge is accomplishing all of this with greater than 1 day of battery running time.

 

The Software will be Updated but the Display Can Not:

The software OS, User Interface, and Apps for smart watches are evolving and improving rapidly, so it isn’t necessary to wait for completed and polished software before buying one – but the display cannot be updated so select it very carefully… We won’t be discussing the software here, just the display. You’ll find lots of software and App reviews and articles elsewhere, but we’ll provide an in-depth analysis of smart watch displays that you will find nowhere else.

 

Smart Watch Display Technologies:

Almost all current smartphones use a backlit LCD or an OLED display – both require battery power to generate their light. They will also work in a smart watch provided the display is On only when you need to look at it – just like a smartphone. That can be done with a manual On button, a touchscreen gesture, or by monitoring the motion and position of the watch and then automatically turning the display On when it is moved to a viewing position. That’s how the Samsung Gear 2 OLED display works. Another approach is to use a reflective display, which can use existing ambient light to keep the screen working and visible at all times without a significant power drain – only requiring an internal light in reduced ambient light conditions. Qualcomm’s Mirasol color display works that way (although the Color Gamut is subdued). LCDs can also be manufactured with a pure reflective mode (like traditional LCD wrist watches), or with a combination of both a backlit transmission mode and a reflective mode, which is called a Transflective LCD. That’s how the Sony SmartWatch 2, Pebble, and Pixel Qi displays work.

 

The Display Shoot-Out:

Here we will test the Sony SmartWatch 2 and the new Samsung Gear 2. In the near future we’ll do a Multi-Display Technology Smart Watch Shoot-Out. To examine the performance of the Sony SmartWatch 2 and Samsung Gear 2 displays we ran our in-depth series of Mobile Display Technology Shoot-Out Lab tests and measurements in order to determine how the displays performed. We take display quality very seriously and provide in-depth objective analysis based on detailed laboratory tests and measurements and extensive viewing tests with both test patterns, test images and test photos.

 

Overview of the Samsung Gear 2:

The Samsung Gear 2 has a 320x320 pixel 1.63 inch RGB Stripe OLED display, touch screen, accelerometer, gyroscope, home button, 2 MP camera, 4GB memory, microphone, speaker, vibrate function, IR LED to act as remote control, heart rate monitor, charging cradle, and Bluetooth communication. The watch is IP67 Dust and Water Resistant (up to 30 minutes in 1 meter of water). It runs under the Tizen OS and works with the Samsung Galaxy S5, Galaxy S4, Galaxy SIII, Galaxy Note 3 and Galaxy Note 2 Smartphones. The user interface is already fairly nice. Samsung provided DisplayMate Technologies with a production unit to test and analyze for this Display Technology Shoot-Out article.

 

Overview of the Sony SmartWatch 2:

The Sony SmartWatch 2 has a much lower resolution 220x176 pixel 1.60 inch Transflective LCD display, touch screen, home button, Ambient Light Sensor, vibrate function, micro USB charge port, NFC and Bluetooth communication. The watch is IP57 Dust and Water Resistant (up to 30 minutes in 1 meter of water). It works with any smartphone running Android 4.0 or later. The user interface is currently quite primitive, but presumably will improve in future updates and upgrades. We purchased this unit retail.

 

Results Highlights

In this Results section we provide Highlights of the comprehensive Lab tests and measurements and extensive visual comparisons using test photos, test images, and test patterns that are covered in the advanced sections. The Lab Tests and Measurements Comparison Table section summarizes the Lab measurements in the following categories:  Brightness and Contrast with Ambient Light,  Color Gamut with Ambient Light,  Screen Reflections,  Viewing Angle Variations. You can also skip these Highlights and go directly to the Conclusions.

 

Battery Running Time:

The small size and weight required for a watch means the battery power is strictly limited. The big question is how long will any particular smart watch run on battery before needing recharging (from either AC or a supplementary battery pack). That will vary considerably based on how frequently a consumer uses it, and the particular Apps that are selected – for that reason we did not test the battery running time for this article. Because of the wide range of consumer uses, multiple display technologies will be needed for smart watches. Conserving and efficiently using battery power and extending the running time involves a number of different approaches and compromises for the displays on smart watches, which we discuss below.

 

Display Performance Specs:

The Lab Tests and Measurements Comparison Table has a detailed set of display specs and measurements.

 

Sharpness: A major difference between the two displays is their screen sharpness: the SmartWatch 2 has a 220x176 pixel screen with 176 ppi and 39K total pixels, while the Gear 2 has a 320x320 pixel screen with 278 ppi and 102K total pixels. The SmartWatch 2 screen was visibly coarse and heavily pixelated (even visible in large text) made worse with poor anti-aliasing, plus the small pixel aperture ratio needed for a Transflective LCD makes it much more noticeable. On the other hand the Gear 2 OLED RGB Stripe display was very sharp, even with fine text and graphics.

 

Brightness: Both displays are fairly bright: the SmartWatch 2 has 495 nits while the Gear 2 has 415 nits in Outdoor mode and 296 nits in Standard mode (Level 5). However, at typical viewing angles (discussed below) the Gear 2 is brighter.

 

Color Gamut and Saturation: The Gear 2 has a very wide color gamut, 135 percent of the sRGB / Rec.709 Standard, which I normally don’t like, but on a small 1.6 inch screen the additional color saturation is not objectionable, and actually compensates for the reduction in color saturation caused by ambient light. So under typical ambient light viewing conditions the Gear 2 color gamut is close to 100 percent. The SmartWatch 2 has a 91 percent color gamut, but it falls drastically with ambient light, and the screen is monochrome in reflective mode.

 

Color Depth: In order to reproduce images well a display needs to be able to display a wide range of intensity levels – most good displays provide 256 intensity levels, which is essential when mixing the red, green and blue primaries to produce all of the necessary on-screen colors. The 256 intensity levels produces 24-bit color. The Gear 2 display has excellent 24-bit color. Sony specs the SmartWatch 2 display at 16-bit color, which has only 32-64 intensity levels, which produces noticeable artifacts in images that have a range of intensities. In a small 1.6 inch display that would normally be fine, but our test images shown below indicate only 16 intensity levels, which is 12-bit color – the lowest I have seen in a very long time, and is simply unsatisfactory as shown next…

 

Screen Shots:

A good way to evaluate the display and compare the image and picture quality is with screen shots of a number of test patterns and test photos on each display. We have included three below: a DisplayMate test pattern with smooth white, red, green and blue intensity ramps, a NASA spacecraft photo of a Sunset on Mars, and a Sony Xperia Demo Photo. Note that the images and displays all have varying aspect ratios. The display on the Samsung Gear 2 accurately and nicely reproduced all three images. The display on the Sony SmartWatch 2 produced poor to horrendous versions of the images, with considerable false contouring and related artifacts, which were quite noticeable even on its small 1.6 inch screen, demonstrating some of the display issues that are discussed above and in the Lab Tests and Measurements Comparison Table. While two of these images are challenging, many of Sony’s own set of (soft) demo photos had easily noticeable image artifacts. Even if you are not interested in looking at photos on your smart watch (it’s nice for quickly showing some family photos) these test images demonstrate important display performance issues.

 

 

Reflective Displays:

While we are all used to having the time always visible on a mechanical wrist watch, that seems hardly necessary for a smart watch, particularly with motion and gesture sensors to automatically turn on the display when the wrist is moved to a viewing position. The always on reflective displays each involve selective performance compromises such as reduced image contrast, color gamut, viewing angle, resolution, and intensity scale, and slower response time. Using a combination transmissive and reflective LCD seems like a good solution, but it comes with a significant performance penalty in both the backlight transmissive mode and the reflective mode that keeps the always on image visible in moderate ambient light, and in many (but not all) high ambient light situations (see below). It remains to be seen how consumers will respond and decide which compromises are tolerable or necessary, so multiple display technologies will undoubtedly be needed for smart watches..

 

Performance in High Ambient Light:

Smart watches are likely to be used more often in higher overall ambient light than smartphones, so how the screen visibility and readability are affected by ambient light is extremely important. Ambient light washes out the screen colors and image contrast. There are a number of ways to improve display performance in ambient light: the two best known are increasing the screen brightness and reducing the screen reflectance. Another is to use extra saturated primary colors and dynamic image contrast to counteract the image washout. But high ambient light will at some point overpower all emissive displays like LCDs and OLEDs. One additional important viewing strategy that we all do automatically is to adjust the angle and position of our wrist to improve watch visibility, and if necessary also rotate so the watch is in our shadow. That works quite well in most circumstances, except in places like the beach.

 

Reflective displays use an entirely different approach by proportionally reflecting the ambient light, so they have a fixed Contrast Ratio (42 for the SmartWatch 2), and in principle are viewable for any level of ambient light, no matter how high. However, one major enemy for all displays, including reflective displays, are mirror (specular) reflections that overlay the display image with distant images that are reflected by the upper layers of the screen. The only solution is again to vary the angles and positions as mentioned above.

 

In its Outdoor mode the Samsung Gear 2 display was readable and usable even in fairly high 40,000 lux outdoor ambient light, but not in direct sunlight. Its strong saturated primary colors also improve high ambient light readability. The Sony SmartWatch 2 display was also very readable at 40,000 lux and above, and even in direct sunlight in its reflective mode. However, for both watches the mirror reflections mentioned above require the display to be carefully oriented to avoid imaged reflections (including possibly your face). See the Brightness and Contrast with Ambient Light and Color Gamut with Ambient Light sections for details.

 

Performance with Viewing Angle:

Almost all displays and display technologies look best when viewed straight on with a zero degree viewing angle – and that’s how most people try to view their smartphones, tablets, notebooks, monitors, and TVs. However, a watch is attached to your wrist, which can only move in a constrained manner, so most of the time it’s easier, more convenient, and more comfortable to hold it at an intermediate viewing angle like 30 degrees. At that viewing angle the Brightness of most LCDs falls by over 55 percent, and the Contrast Ratio falls even more, by over 75 percent, while OLEDs experience only a 20 percent decrease in both. As a result, the SmartWatch 2 LCD display has a drastic performance decrease at typical viewing angles, but the Gear 2 OLED display experiences only a relatively small one. While the SmartWatch 2 is considerably brighter at 0 degrees, the Gear 2 is brighter and has a much higher Contrast Ratio at typical viewing angles. See the Viewing Angle Variations section for details.

 

Smart Watch Conclusions

The performance differences between the displays in these two top tier second generation smart watches are surprisingly quite large.

 

The OLED display on the Samsung Gear 2 performed very well across the board, almost identically to the most recent Galaxy S OLED Smartphones in almost every test measurement and viewing category. It looked and performed like a small version of a high quality OLED smartphone display – including sharpness, high pixels per inch, brightness, color depth, color gamut, viewing angle, in ambient light, and overall image and picture quality. For details see the Lab Tests and Measurements Comparison Table and also the Screen Shots above.

 

On the other hand, the Transflective LCD display on the Sony SmartWatch 2 was quite disappointing across the board, especially for a 2nd (actually 3rd) generation device. To easily see that examine the mediocre to poor results in the detailed Lab Tests and Measurements Comparison Table and also in the Screen Shots above. In particular, the coarse and heavily pixelated low resolution and low pixels per inch screen made worse with poor anti-aliasing, the very low color depth, the poor color gamut in ambient light, and also the poor viewing angle performance (because watches are not easily positioned for zero degree viewing). Using a combination Transflective LCD comes with a significant performance penalty in both the backlight transmissive mode and the reflective mode that keeps the always on image visible in moderate ambient light and in some but not all high ambient light situations. The choices and compromises made by Sony for the SmartWatch 2 display simply do not work well. The (rumored) upcoming (presumably) LCD smart watches from LG and Apple will undoubtedly perform considerably better…

 

What’s Next…

The early adopters have been enjoying their smart watches for quite some time. The display is clearly the most important and key component in a smart watch, and the current Samsung Gear 2 already has an excellent display. We’ll revisit smart watch displays again soon when the highly anticipated products from Apple, LG, and others arrive. The software OS, User Interface, and Apps for all smart watches will continue to improve rapidly with downloadable updates. It will be really interesting to see what other display technologies and strategies are introduced for smart watches, the consumer responses to them, and how they will evolve over time. We’ll see more reflective, transflective, curved, and bendable smart watch displays in the near future, and also microLED smart watch displays in the not too distant future. There is no doubt that smart watches will be taking over from mechanical wrist watches, and most likely much sooner than most people think…

 

Display Shoot-Out Comparison Table

Below we examine in-depth the displays on the Sony SmartWatch 2 and Samsung Gear 2 smart watches based on objective Lab measurement data and criteria.

 

For details and additional information on all the measurements see our Galaxy S5 Display Technology Shoot-Out article.

For comparisons with the other leading displays including LCDs see our Mobile Display Technology Shoot-Out series.

 

Categories	Sony SmartWatch 2	Samsung Gear 2
Display Technology	Transflective LCD Low Pixel Aperture Ratio	Super AMOLED RGB Stripe
Display Size	1.60 inches Diagonal 1.25 x 1.00 inches	1.63 inches Diagonal 1.15 x 1.15 inches
Display Aspect Ratio	5:4 = 1.25 Landscape	1:1 = 1.00 Square
Display Resolution	220 x 176 pixels	320 x 320 pixels
Total Number of Pixels	38,720 pixels	102,400 pixels
Pixels Per Inch	176 ppi	278 ppi
20/20 Vision Distance where Pixels are Not Resolved	19.5 inches	12.4 inches
Text and Graphics	Coarse and Visibly Pixelated Poor Anti-Aliasing Low Pixel Aperture Ratio	Very Sharp
Display Hardware Color Depth	Contradictory Sony Specs “16-bit color with 262K Colors” is either 18-bit color with 262K Colors 16-bit color with   65K Colors with 32 or 64 Intensity Levels	Samsung Specs   24-bit color with 16.8M Colors 256 Intensity Levels
Photo Viewer Color Depth	12-bit color 16 intensity Levels 4,096 Colors Severe False Contouring Visible in Many Images	24-bit color 256 Intensity Levels 16.8 Million Colors
Brightness and Contrast with Ambient Light At 0 degrees Viewing Angle. But the typical Viewing Angle for a Watch is actually 30 degrees or more. See below.
Maximum Brightness	495 cd/m2 with Backlight	415 cd/m2 Outdoor Mode   296 cd/m2 Standard Mode
Black Brightness at 0 lux at Maximum Brightness	0.52 cd/m2 with Backlight Dynamic Backlight	0 cd/m2
Contrast Ratio Measured in the dark at 0 lux	952 with Backlight at 0 lux Decreases with Ambient Light	Infinite at 0 lux Decreases with Ambient Light
Contrast Ratio Measured in Ambient Light	with Backlight 60 at    500 lux 31 at 1,000 lux 16 at 2,000 lux   42 in Reflective Mode Varies with the Light Distribution	Outdoor Mode 51 at    500 lux 26 at 1,000 lux 13 at 2,000 lux   Standard Mode 37 at    500 lux 19 at 1,000 lux 10 at 2,000 lux
Color Gamut with Ambient Light The Image Colors depend on the Ambient Light and Viewing Angle. See below.
Color of White Color Temperature in degrees Measured in the dark at 0 lux   6,500 K is best for Photos and Videos	7,446 K with Backlight Somewhat Too Blue for Accurate Image Colors   Yellowish in Reflective Mode Depends on the Ambient Light	7,539 K Somewhat Too Blue for Accurate Image Colors
Color Gamut Measured in the dark at 0 lux     Most consumer content uses the sRGB / Rec.709 Gamut	91 percent with Backlight sRGB / Rec.709 Decreases with Ambient Light   Monochrome in Reflective Mode	135 percent sRGB / Rec.709 Decreases with Ambient Light   Large for Photos But OK on a Small Screen
Color Gamut Measured in Ambient Light	with Backlight 70 percent at    500 lux 56 percent at 1,000 lux 38 percent at 2,000 lux   Monochrome in Reflective Mode	Outdoor Mode 120 percent at    500 lux 107 percent at 1,000 lux   86 percent at 2,000 lux   Standard Mode 114 percent at    500 lux   97 percent at 1,000 lux   73 percent at 2,000 lux
Screen Reflections The Screen Reflects Ambient Light, which washes of the Image Contrast and Colors.
Average Screen Reflection Light from All Directions	5.3 percent Very Good	4.7 percent Excellent
Mirror Reflections Percentage of Light Reflected	6.8 percent Very Good	6.9 percent Very Good
Contrast Rating for High Ambient Light The Higher the Better	93 with Backlight also has a Reflective Mode	88 Outdoor Mode 63 Standard Mode
Viewing Angle Variations The typical Viewing Angle for a Watch is actually about 30 degrees or more from exactly face on.   The Brightness generally decreases, the Black Level generally increases, and the Image Colors Shift. See this Figure for an explanation and visual definition of JNCD.
Maximum Brightness at a 30 degree Viewing Angle	203 cd/m2 with Backlight	324 cd/m2 Outdoor Mode   231 cd/m2 Standard Mode
Brightness Decrease at a 30 degree Viewing Angle	59 percent with Backlight Very Large Decrease	22 percent Small Decrease
Black Level Increase at a 30 degree Viewing Angle	126 percent with Backlight Very Large Increase	0 percent No Change
White Point Color Shift at a 30 degree Viewing Angle	Small Color Shift Δ(u’v’) = 0.0081 2.0 JNCD	Small Color Shift Δ(u’v’) = 0.0077 1.9 JNCD
Color Shifts Primary Colors and Mixtures at a 30 degree Viewing Angle	Large Color Shift Largest Shift Δ(u’v’) = 0.0515 12.9 JNCD	Medium Color Shift Largest Shift Δ(u’v’) = 0.0250 6.2 JNCD

 

 

 

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

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About DisplayMate Technologies

DisplayMate Technologies specializes in proprietary advanced 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 Smartphone and Smartphone mobile 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. We help manufacturers with expert display procurement, prototype development, and production quality control so they don’t make mistakes similar to those that are exposed in our Display Technology Shoot-Out series. 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. 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.

 

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Copyright © 1990-2014 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