Apple Watch Display Technology Shoot-Out

Dr. Raymond M. Soneira

President, DisplayMate Technologies Corporation

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Apple Watch

Introduction

The smart watch revolution is now fully underway, with the Apple Watch rounding out the offerings from all of the current major players. An advanced display is what makes a smart watch possible by providing high resolution high pixel density bitmap graphics and text images sharply displayed on a tiny screen. In fact, the displays needed for smart watches are right at the cutting edge of display technology, and they determine how good everything will look on the watch – the display is literally the crown jewel of the smart watch.

The display on the Apple Watch rises to the challenge with an excellent state-of-the-art Flexible OLED display covered by a sapphire crystal, or by an Ion-X strengthened cover glass for the Sport model. Also very significant, it is Apple’s first OLED display, which are often more challenging to engineer than using long established LCDs. We will examine, lab test, and analyze the Apple Watch display with a sapphire crystal below…

But why are the displays for smart watches so challenging? First of all, they are tiny displays, typically around 1.5 inches (38 mm) across, yet they still should have at least 250x250 pixels or more, with many providing 320 pixels and even reaching up as high as 480 pixels. Plus, the display is expected to fill almost the entire watch face so there isn’t much room allowed for a bezel, so the display itself must have very narrow borders along all the outside edges. Plus, it must be very bright in order to be readable outdoors, be very thin because the entire watch has to fit nicely and unobtrusively on your wrist, and be very power efficient because the display is the single biggest power drain for the watch and determines the size battery that is needed to keep it running for at least a full day.

Smart Watch Display Performance

One especially important point to bear in mind when selecting any smart watch is that while the software and apps will be updated, refined and improved, the display on a smart watch will remain the same and can not be updated – so pay particular attention to the quality and performance of the display on any smart watch you are considering!

Surprisingly, Apple has said very little about the display on the Apple Watch. For their other products, like the iPhone 6 for example, Apple provides detailed display specs including the screen size, pixel resolution, brightness, contrast ratio, color gamut, and viewing angles on their website. For the Apple Watch they mention none of these, not even the display technology, just that it’s a “Flexible Retina Display.” We’ll fill you in on all of these together with in-depth lab performance tests.

In this article we will cover everything related to the display on the Apple Watch in-depth, but we won’t review its processor or communication functions, its apps, user interface and software, or consider its fashion and design aspects as stylish jewelry. You can read about all of these elsewhere…

Traditional Mechanical Watch Displays

All traditional mechanical watches use a motor to move the hands and accessory widgets (like the date and day of the week). Their display simply works by reflecting ambient light off the watch face – so they are very easy to read in bright ambient light, but invisible in the dark. The electronic display on a smart watch can show the time in a zillion different ways, but on many smart watches the display still simulates a traditional mechanical watch face, however, an unlimited number of designs and styles are possible.

While the traditional mechanical watch display can show the time in only one way, it does that extremely well – the display is always on, it has very sharp and often elegant watch face graphics, it is easy to read in high ambient light, including direct sunlight, has great viewing angles, can fit inside a fairly thin case, and the electric drive models have very low power consumption. In fact, my Citizen Eco-Drive watch is 9 years old and has never needed a battery replacement because it is automatically recharged by a built-in photocell in ordinary ambient light.

Display Technologies for Smart Watches

Given the extent that traditional mechanical watches have been refined over the last century, the displays on smart watches have some pretty challenging performance criteria to match or beat. For some performance issues they are still not as good as traditional watches, but overall the latest and best smart watch displays can already deliver excellent performance that we will examine in detail below, plus they are continuing to improve.

So which are the most attractive display technologies for a smart watch? There are currently two that are very well suited for smart watches – LCD and OLED. Other display technologies are also being used, including e-ink (Seiko Spirit watch), e-paper (Pebble watches actually use a transflective memory LCD), and mirasol (Qualcomm Toq watch). These displays all work by reflecting ambient light, which provides major screen readability advantages in bright light, plus they require very low power, so they have much longer running times on battery. However, due to major advancements in LCD and OLED displays they are no longer mainstream in the current market. Our discussion below will focus on the latest generation of watch displays with at least 250x250 pixels.

LCD displays have been in digital watches all the way back to the 1980s, but the first LCD smart watches were introduced in 2014, including (alphabetically) the LG G Watch, the Motorola Moto 360, and the Sony SmartWatch 2 and 3. Manufacturing small and thin LCDs for a smart watch is very challenging because they are made up of many layers including a backlight, two light polarizers, various optical films in addition to the two glass sheets that sandwich the active Liquid Crystal layer. As a result, LCDs for watches tend to be much thicker than OLEDs, typically over 2.0 mm, and also have a wide rim because the LCD drive signals must enter along the outer edges since the visible part of the LCD display must transmit the backlight.

OLED displays are an ideal technology for smart watches because they are thin single layer solid-state displays with high pixels-per-inch (ppi) that can be manufactured and cut into small smart watch sized screens with resolutions of 320x320 pixels and above. They offer much better black levels, viewing angles, and power management compared with LCDs. In 2013 Samsung introduced the first OLED smart watch, the Galaxy Gear, with 320x320 pixels and full 24-bit color. The Galaxy Gear 2 was introduced in 2014, and performed very well in our Display Shoot-Out tests. These OLED displays are made on a rigid substrate like almost all smartphone displays. They are fairly thin at just 0.9 mm and can be made with a very narrow rim and bezel, which are major advantages over LCDs. But the newest Flexible OLED displays have evolved way beyond this…

Flexible OLED displays are the latest advancement in OLED technology. They are made on a flexible plastic substrate, so they can be used to make curved displays. But they also provide major advantages for flat screen watches because they are extra thin, typically less than 0.5 mm, much lighter in weight, plus the flexible substrate makes it possible to enclose them into a smaller space. LG and Samsung are the leaders in this display technology. In 2013 both introduced Flexible OLED smartphones (the Samsung Galaxy Round and the LG G Flex) and in 2014 both introduced Flexible OLED smart watches (the Samsung Gear S, which has a curved display, and the LG G Watch R, which has a full circle round display, which is only possible using an OLED plastic substrate). Note that on the Apple Watch the Flexible OLED display is bonded to the sapphire crystal or cover glass, so it isn’t flexible from the outside.

Sapphire Crystal

The Apple Watch Sport model has its display cover made from “Ion-X” strengthened scratch resistant glass, the same as the iPhone 6 and 6 Plus (and very similar if not identical to Corning Gorilla glass). However, the Apple Watch and Watch Edition instead have a sapphire crystal, the same as on most high-end traditional watches, because it is extremely scratch resistant and almost scratch proof under normal use.

But a major issue for sapphire is that it reflects about twice as much ambient light as glass (due to fundamental principles of physics and optics). That is not a problem for traditional watches because their displays actually work by reflecting ambient light, so the extra light reflected by the sapphire crystal on top is a minor issue. On the other hand, it is a major issue for smart watch displays because doubling the amount of reflected light will significantly wash out the display’s own image light, reducing both contrast and color saturation, and making it harder to see the image. So for smart watch displays, but not for traditional mechanical watches, sapphire comes with a significant display performance cost. We’ll measure and discuss this in detail below.

The Apple Watch is being promoted by Apple as having a “Flexible Retina Display” which is an OLED with high pixels-per-inch (ppi), and is most likely being made by LG Display. It is very interesting and exciting that Apple has chosen to use a true cutting edge state-of-the-art display in their first watch. We’ll cover all of these issues and much more, with in-depth comprehensive display tests, measurements and analysis that you will find nowhere else.

The Display Shoot-Out

In our first Smart Watch Display Shoot-Out article we tested and compared the OLED display on the Samsung Gear 2 and the LCD display on the Sony SmartWatch 2. For this Display Shoot-Out article we test the Apple Watch display in-depth. To examine the display performance for the smart watches 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.

Results Highlights

In this Results section we provide Highlights of the comprehensive DisplayMate Lab tests and measurements and extensive visual comparisons using test photos, test images, and test patterns that are covered in the advanced sections. The Display Shoot-Out Comparison Table summarizes the Apple Watch and iPhone 6 Lab measurements in the following categories: Screen Reflections, Brightness and Contrast with Ambient Light, Color Gamut with Ambient Light, Viewing Angle Variations. You can also skip these Highlights and go directly to the Apple Watch Conclusions.

Overview of the Apple Watch Display

The Apple Watch comes in 3 models and two sizes – we tested the larger 42 mm Apple Watch model, which has a sapphire crystal. All models and sizes have a Flexible OLED display, which is most likely being made by LG Display. The resolution for the 42 mm size is 312x390 pixels. The sub-pixel arrangement is RGB Stripe. The screen Aspect Ratio is 4:5=0.80 so it is a portrait style display rather than perfectly square or round like most watch displays.

A Retina Display

Apple hasn’t published the actual display size, so we carefully measured it with a digital caliper. The display screen is 30.8 x 24.6 mm (1.21 x 0.97 inches) with a diagonal of 38.7 mm (1.53 inches). Note that the display corners are all slightly rounded off. That works out to 322 pixels-per-inch (ppi), which is virtually identical to the iPhone 6 (and could be identical due to the measurement error). That falls right in with Apple’s Retina Display classification, which means that for normal 20/20 Vision the pixels are not resolved and the display appears perfectly at typical viewing distances. For 322 ppi, this applies for viewing distances greater than 10.7 inches (27 mm), which is applicable for a wrist watch.

Watch Color Gamut and Color Management

OLED displays, like on the Apple Watch, typically have a rather wide native Color Gamut due to the properties of the materials used to make OLEDs. That results in some highly saturated colors, which are actually helpful for viewing under bright ambient light, but it then introduces noticeable color errors when looking at standard content (particularly photos and videos) under typical indoor lower lighting levels.

The Lab measurements indicate that Apple decided that the Apple Watch should have an appearance and Color Gamut close to the iPhone 6, so the watch has Color Management implemented in order to adjust the OLED Color Gamut, particularly the Green primary (by adding the proper admixtures of Red and Blue to each Green sub-pixel). Samsung uses the same approach for its color accurate Basic and Cinema screen modes. The Apple Watch and iPhone 6 Color Gamuts are shown in Figure 1 along with the sRGB/Rec.709 Standard that is used for almost all current consumer content. As we discuss next, their color agreement is very good, which is important because the Apple Watch and iPhone 6 will often be used side-by-side, so they should look the same. See the Color Gamut section and Figure 1 for measurements and details.

Watch Color Accuracy

The Apple Watch provides a very good color match to the iPhone 6 as shown in Figure 1. For the most important Red and Green primaries the agreement is excellent. The Blue Primaries differ somewhat, but as we have explained in our Absolute Color Accuracy Display Shoot-Out article, color errors in Blue are much less important and noticeable than for Red and Green. Another important issue for high image quality is the color and intensity bit depth – and the Apple Watch delivers Full 24-bit color, like the iPhone 6.

Both the Apple Watch and iPhone 6 have slightly Bluish White Points with about 7,200K Color Temperature instead of the standard D6500. As discussed above it’s important that they be consistent, so that’s fine, however it reduces their absolute color accuracy. Another issue, which we discuss below is that the Bluish White Point decreases display power efficiency of the watch OLED display. Overall the Apple Watch delivers comparable Very Good Absolute Color Accuracy like the iPhone 6. See our Absolute Color Accuracy Display Shoot-Out article for details.

Ambient Light Sensor

Most mobile displays come with an Ambient Light Sensor that samples the ambient light falling on the screen and then automatically adjusts the display brightness up and down to try to improve viewing comfort (so it’s not too dim or too bright) and also to regulate the power used by the display. This Power Management Function is especially important for the watch in order to maximize the running time on battery. In fact, it is so important that Automatic Brightness can not be turned off like on iPhones and iPads to prevent a fixed manual brightness setting, which would run down the battery more quickly. Apple does provide 3 settings: low, medium and high settings, but Automatic Brightness can not be overridden, so if you find the screen too dim for your liking you’ll just have to shade the watch somehow to see the screen.

On most mobile displays the Ambient Light Sensor is located on the outer bezel near the top center. Apple has taken an innovative approach and placed the sensor behind the display, which is possible with a plastic OLED display. One side effect is that the sensor is affected by the current image content appearing on the display, which introduces some variability in the resulting Brightness settings. However, as the ambient light level increases this variability is much less of a factor.

Watch Display Brightness

With running time on battery being such an important issue, it’s not surprising that Apple has implemented a rather aggressive Brightness management strategy. At lower indoor ambient light levels the display’s Brightness (Luminance) is satisfactory. For the 3 level 1/2/3 user Brightness settings for the Apple Watch the display has 15/60/80 nits at 0 lux, which are good for very low light. As the lux level increases the display Brightness then increases at different rates, but all three settings eventually reach a maximum of 482 nits at very high ambient lux light levels, which is impressive for a watch. But for intermediate lux levels it can be iffy: for example, for the highest (3) user setting, the display reaches 203 nits at 500 lux, 203 nits also at 1,000 lux, and 290 nits at 2,000 lux. In some cases you will need to position your wrist into your shadow in order to see the display well. Indoors it’s fine, outdoors it can be iffy like on most mobile displays. See the Brightness section for measurements and details.

Sapphire Crystal and Reflectance

The Apple Watch Sport model has its display cover made from “Ion-X” strengthened scratch resistant glass, the same as the iPhone 6. However, the Apple Watch and Watch Edition instead have a sapphire crystal, the same as on most high-end traditional watches, because it is extremely scratch resistant and almost scratch proof under normal use.

However, sapphire reflects about twice as much ambient light as glass (due to fundamental principles of physics and optics). Since any reflected ambient light decreases image contrast and color saturation, displays with sapphire can’t perform as well as the lower Reflectance glass in ambient light. While Anti-Reflection coatings are used to lower the Reflectance of camera lenses and other optical components, the coatings scratch relatively easily, so they can’t be used for a watch because they would defeat sapphire's tremendous scratch resistance. A specially treated Enhanced Sapphire will soon be available that delivers both high scratch resistance and low Reflectance, which we will discuss further in the Conclusions.

We measured the Reflectance of the Apple Watch with a sapphire crystal to be 8.2 percent, (0.5 percent greater than the single surface Reflectance of sapphire in air), indicating that Apple has done an excellent job in optically bonding the sapphire to the OLED display without an air gap. However, the Reflectance of the iPhone 6 with Ion-X cover glass is only 4.6 percent, so the Apple Watch with a sapphire crystal reflects 178 percent of the amount of light reflected by the iPhone 6. We didn’t test the Apple Watch Sport with Ion-X glass, but expect similar results to the iPhone 6.

Note that many of the measurements for the Apple Watch depend to varying degrees on whether it has a sapphire crystal or Ion-X cover glass, which we have identified with a Sapphire label in the Display Measurements Comparison Table. See the Reflections section for measurements and details.

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Watch Performance in 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. Reflected 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 OLEDs and LCDs. 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.

With running time on battery being such an important issue, Apple has implemented a rather aggressive Brightness management strategy for the Watch, which holds down the display Brightness as much as possible. This significantly reduces the Contrast Ratio and Color Gamut as the ambient light level increases. For example, at 500 lux, which corresponds to bright indoor lighting, the Apple Watch Contrast Ratio has fallen to 17 and the Color Gamut to 69 percent. For the iPhone 6 set to Maximum Manual Brightness, at the same 500 lux the Contrast Ratio is 76 and the Color Gamut is 90 percent. However, when the iPhone 6 is set to Fully Automatic Brightness (without any manual slider overrides) it performs about the same as the Apple Watch. But the iPhone 6 allows the Automatic Brightness to be pushed up or down, providing much greater user control in adjusting the Brightness. See the Brightness and Contrast with Ambient Light and Color Gamut with Ambient Light sections for details.

Watch Viewing Angle Performance

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 30 degree Viewing Angle the Brightness of most LCDs falls by over 55 percent, while OLEDs typically experience only a 20 percent decrease. However, the Apple Watch with a sapphire crystal experiences a larger 32 percent Brightness decrease and also larger Color Shifts than other OLED displays because sapphire has much higher optical depth than glass. The Brightness and Color Shifts become larger with Viewing Angle and can be quite noticeable at 45 degrees and above. The Brightness and Color Shifts will be much smaller with the Ion-X cover glass for the Apple Watch Sport model, but we did not test that model. See the Viewing Angle Variations section for details.

Viewing Tests

The Apple Watch provides very nice, pleasing and accurate colors and picture quality, and is a very good side-by-side match to the iPhone 6. Even on its small 1.5 inch display, the very challenging set of DisplayMate Test and Calibration Photos that we use to evaluate picture quality looked Beautiful, even to my experienced hyper-critical eyes. Even the Test Patterns were accurately reproduced and artifact free with excellent calibration and rescaling to the Apple Watch’s native 390x312 resolution. All of the images appeared very sharp on the relatively high pixels-per-inch (ppi) screen. Well done!

Watch Display Power Management

One major advantage of OLED displays is their per pixel power management. With most LCDs the entire backlight must be turned on even if only a single sub-pixel needs to be activated. On the other hand, for OLEDs each individual sub-pixel is independently powered, which provides tremendous flexibility in display power management. An all black OLED display uses no power, and a screen with a black background will use only a small amount of power compared to an white background. That’s why it’s better to have a black background on mobile OLED displays. In addition, a black background improves screen readability in high ambient light compared to a white background.

All OLED and LCD mobile displays need to carefully manage their power by controlling display brightness and by turning off the display when it is not needed or being watched. This is especially important for smart watches with their tiny batteries. We will discuss these power management strategies further in the Conclusions section, below..

Apple Watch Display Conclusions

The primary goal of this Display Technology Shoot-Out article series has always been to publicize and promote display excellence so that consumers, journalists and even manufacturers are aware of and appreciate the very best in displays and display technology. We point out which manufactures and display technologies are leading and advancing the state-of-the-art for displays by performing comprehensive and objective scientific Lab tests and measurements together with in-depth analysis. We point out who is leading, who is behind, who is improving, and sometimes (unfortunately) who is back pedaling… all based solely on the extensive objective careful Lab measurements that we also publish, so that everyone can judge the data for themselves as well… See the Apple Watch Display Shoot-Out Comparison Table for all of the Lab measurements and testing details, and the Results Highlights section above for a more general overview with explanations.

An Excellent Smart Watch Display!

The key element for a great smart watch is its display… and Apple has done a great job with the OLED display on the Apple Watch. It provides very nice, pleasing and accurate colors and picture quality, and is a very good side-by-side match to the iPhone 6. It is very nicely implemented and an Excellent Smart Watch Display!

Even the challenging DisplayMate Test Patterns were accurately reproduced and artifact free with excellent calibration and rescaling to the Apple Watch’s native 390x312 resolution. All of the images appeared very sharp on the relatively high pixels-per-inch (ppi) screen. Well done!

A major issue for all smart watches is the limited display Brightness, the performance in high ambient light, display power management and the running time on battery. The Lab measurements show that these are also major issues with the Apple Watch as well. For details see the Lab Tests and Measurements Comparison Table.

First: Apple has implemented a rather aggressive display Brightness and display power management strategy using a mandatory Automatic Brightness Ambient Light Sensor that significantly restrains the display’s Brightness. While satisfactory for low indoor ambient lighting it significantly reduces the Contrast Ratio and Color Gamut as the ambient light level increases and there is no way for the user to make any adjustments other than just shading the watch somehow. Another form of aggressive display power management is turning off the display after 6 to 17 seconds, which is rather inflexible and can be very annoying, and it interferes with some uses of the watch. More on power management below…

Second: the premium Apple Watch models have a sapphire crystal rather than using a cover glass like on the iPhone 6 and most smartphones. That is the same approach used on premium traditional watches, but there is one very significant difference between them. The much higher Reflectance of sapphire compared to glass almost doubles the reflected ambient light, which is fine for traditional watches that work by reflecting ambient light, but significantly washes out the image contrast and color on emissive smart watch displays. It’s an interesting compromise between the luxury and scratch resistance of sapphire versus optical performance. More on sapphire below…

The Apple Watch is Apple’s first OLED display, which is a very interesting development, and who knows where it might lead in future displays for Apple smartphones, tablets, and monitors. While LCDs make excellent displays for smartphones, tablets, monitors and TVs, there is absolutely no question that for smart watches, OLED is the only way to go for a great display, and it’s very significant that Apple has chosen an OLED for its first Apple Watch display!

Enhanced Sapphire

While sapphire is incredibly hard and scratch resistant, the Lab measurements have demonstrated that it significantly affects the optical performance of (emissive) smart watch displays compared to glass, particularly in high ambient light and for large viewing angles. This behavior is very different from sapphire as it is used in traditional watches, which work by light reflection and not by display emission. In order to increase the use of sapphire for displays, the sapphire industry will need to modify the optical properties of sapphire without significantly affecting its scratch resistance and other mechanical properties. It can’t be done using traditional Anti-Reflection optical coatings which scratch easily. A specially treated Enhanced Sapphire will soon be available that delivers both high scratch resistance and low Reflectance. We will provide more information on Enhanced Sapphire in our upcoming 2015 Innovative Displays and Display Technologies article. Here is a link to the 2014 Edition.

Watch Software will be Updated and Improved but the Display will Remain the Same

One especially important point to bear in mind when selecting any smart watch is that while the software and apps will be updated, refined and improved, the display on a smart watch will remain the same and can not be updated – so pay particular attention to the quality and performance of the display on any smart watch you are considering!

Apple Watch Comparison with the iPhone 6

Since the Apple Watch is often used right next to the iPhone 6, Apple has gone to considerable lengths to give them the same colors, color calibration, and color accuracy. The two most significant differences (other than size) are the much higher Reflectance of the Apple Watch with a sapphire crystal (8.2 percent compared to 4.6 percent), and the aggressive Brightness control using a mandatory Automatic Brightness Ambient Light Sensor in order to increase the running time on battery for the tiny watch.

Apple Watch Comparison with other Smart Watches

The only other OLED smart watch that we have tested so far in our public Display Technology Shoot-Out article series is the Samsung Gear 2, which also has a very impressive and excellent display with Full 24-bit color, but with the following principal differences with the Apple Watch: the Color Gamut is similar to the wider Adobe RGB rather than sRGB, it has Gorilla Glass with a very low 4.7 percent Reflectance rather than sapphire with 8.2 percent Reflectance, it does not have an Ambient Light Sensor or Automatic Brightness, which allows the user to set the desired Brightness as high as they like, resulting in much higher Contrast Ratios and Color Gamuts in ambient light, and also better Viewing Angle Performance. To compare them in detail click the following two links in a tabbed web browser: Samsung Gear 2 and Apple Watch.

Recommendations for Enhanced Watch Displays

4 of the 6 Recommendations below can be implemented in software for existing smart watches.

· The best way to improve screen readability in ambient and also increase the running time on battery at the same time is to significantly reduce the screen Reflectance for both sapphire and glass as we have discussed above.

· Enlarging the Color Gamut for high ambient light is another way to improve display performance in ambient light without increasing display power, and then using Dynamic Color Management at lower ambient light levels.

· Implement Automatic Brightness in a way that allows some degree of manual adjustment as on the iPhone 6 as discussed above.

· For OLEDs, Blue is by far the least power efficient primary drive color, so it is desirable to reduce the Blue drive levels whenever possible. Just lowering the White point down to the Standard 6,500K from the Bluish 7,200K can save almost 10 percent on display power.

· For OLEDs, going a step further and turning off the least efficient Blue drive entirely, producing a Red-Yellow-Green color space, would produce a 35 percent display power savings for the same Luminance. Going even further and in addition turning off the Red drive and just using the most efficient Green primary would produce a 55 percent display power savings for the same Luminance. For some situations and applications this would be very helpful and can be used to improve both screen Brightness and running time on battery.

· Allow users to set the length of time before the display is turned off. For the Apple Watch simply fixing it to 6 seconds for wrist motion and 17 seconds for interactive actions is inflexible and can be very annoying, and it interferes with some uses of the watch. Both permanent and temporary time extensions should be allowed under user control. This applies to most smart watches.

Apple Watch

Display Shoot-Out Comparison Table

Below we examine in-depth the display on the Apple Watch based on objective Lab measurement data and criteria.

We have also included results for the display on the Apple iPhone 6 – although considerably larger it is the primary display that will often be near the Apple Watch, so it’s important to know how well they compare and perform.

Note that all measurements for the Apple Watch differ to varying degrees for the Sapphire crystal and Ion-X Glass.

We have marked the most significant variations with a Sapphire label.

For additional information on OLED display measurements see our Galaxy S6 Display Technology Shoot-Out article.

For comparisons with Samsung and Sony Smart Watches see our Smart Watch Display Technology Shoot-Out article.

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

Categories Apple Watch 42 mm with Sapphire Crystal Apple iPhone 6 with Ion-X Glass Display Technology Flexible OLED RGB Stripe IPS LCD RGB Stripe Display Shape 4:5 = 0.80 Portrait Only 9:16 = 0.56 or 16:9 = 1.78 Portrait or Landscape Display Size 1.53 inches Diagonal 1.21 x 0.97 inches with rounded corners 4.7 inches Diagonal 4.09 x 2.30 inches Display Area 1.2 square inches 9.4 square inches Relative Display Area 100 percent 802 percent Display Resolution 390 x 312 pixels 1334 x 750 pixels Total Number of Pixels 122K pixels 1,000K pixels Pixels Per Inch 322 ppi 326 ppi 20/20 Vision Distance where Pixels are Not Resolved 10.7 inches 10.5 inches Appears Perfectly Sharp at Typical Viewing Distances Yes Apple Retina Display Yes Apple Retina Display Text and Graphics Very Sharp Very Sharp Display Color Depth Full 24-bit color Full 24-bit color Screen Reflections The Screen Reflects Ambient Light, which washes of the Image Contrast and Colors. The Average Reflectance is measured with an Integrating Hemisphere and Spectroradiometer. The Mirror Reflections are measured with a highly collimated beam of light and Spectroradiometer. The Reflectance of Sapphire is much higher than Glass. Average Screen Reflection Light from All Directions with Sapphire 8.2 percent Good 4.6 percent Excellent Relative Brightness of the Reflected Ambient Light 178 percent 100 percent Mirror Reflections Percentage of Light Reflected with Sapphire 9.2 percent Good 6.0 percent Very Good Contrast Rating for High Ambient Light The Higher the Better with Sapphire Up to 59 Good Automatic Light Sensor 121 Excellent Maximum Brightness Setting Apple Watch 42 mm Apple iPhone 6 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 Up to 482 cd/m2 Automatic Light Sensor 558 cd/m2 Manual or Automatic Sensor Black Brightness at 0 lux at Maximum Brightness 0 cd/m2 Increases with Ambient Light 0.35 cd/m2 Increases with Ambient Light Contrast Ratio Measured in the dark at 0 lux Infinite at 0 lux Decreases with Ambient Light 1,592 at 0 lux Decreases with Ambient Light Auto Brightness Level Measured in Ambient Light Maximum Brightness Setting with Automatic Light Sensor 203 cd/m2 at 500 lux 203 cd/m2 at 1,000 lux 290 cd/m2 at 2,000 lux 482 cd/m2 at High lux with Automatic Light Sensor 110 cd/m2 at 500 lux 137 cd/m2 at 1,000 lux 180 cd/m2 at 2,000 lux 558 cd/m2 at High lux Contrast Ratio Measured in Ambient Light Maximum Brightness Setting with Automatic Light Sensor 17 at 500 lux 9 at 1,000 lux 7 at 2,000 lux with Automatic Light Sensor 16 at 500 lux 11 at 1,000 lux 7 at 2,000 lux with Maximum Manual Setting 76 at 500 lux 39 at 1,000 lux 20 at 2,000 lux Apple Watch 42 mm Apple iPhone 6 Color Gamut with Ambient Light The Image Colors depend on the Ambient Light and Viewing Angle. Color of White Color Temperature in degrees Measured in the dark at 0 lux 7,145 K Slightly Too Blue Lower OLED Power Efficiency 7,241 K Slightly Too Blue for Accurate Image Colors Color Gamut Measured in the dark at 0 lux See Figure 1 104 percent at 0 lux sRGB / Rec.709 Decreases with Ambient Light See Figure 1 101 percent at 0 lux sRGB / Rec.709 Decreases with Ambient Light See Figure 1 Color Gamut Measured in Ambient Light with Automatic Light Sensor 69 percent at 500 lux 49 percent at 1,000 lux 39 percent at 2,000 lux with Automatic Light Sensor 62 percent at 500 lux 50 percent at 1,000 lux 38 percent at 2,000 lux with Maximum Manual Setting 90 percent at 500 lux 82 percent at 1,000 lux 68 percent at 2,000 lux Apple Watch 42 mm Apple iPhone 6 Viewing Angle Variations The typical Viewing Angle for a Watch is actually about 30 degrees or more from exactly face on. See this Figure for an explanation and visual definition of JNCD. The Viewing Angle Variations for Sapphire are much higher than for Glass. Brightness Decrease at a 30 degree Viewing Angle with Sapphire 32 percent Medium Decrease 44 percent Portrait 57 percent Landscape Very Large Decrease Typical for all LCDs Black Level Change at a 30 degree Viewing Angle 0 percent No Change for OLED 8 percent Slight Decrease at 30 degrees White Point Color Shift at a 30 degree Viewing Angle Small Color Shift Δ(u’v’) = 0.0102 2.5 JNCD with Sapphire Small Color Shift Δ(u’v’) = 0.0037 0.9 JNCD Color Shifts Primary Colors and Mixtures at a 30 degree Viewing Angle Medium Color Shift Largest Shift Δ(u’v’) = 0.0375 9.4 JNCD with Sapphire Small Color Shift Largest Shift Δ(u’v’) = 0.0052 1.3 JNCD Categories Apple Watch 42 mm with Sapphire Crystal Apple iPhone 6 with Ion-X Glass

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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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, smart watches, 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 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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