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7 inch Tablet Display Technology Shoot-Out

Amazon Kindle Fire HD  –  Google Nexus 7

 

Dr. Raymond M. Soneira

President, DisplayMate Technologies Corporation

 

Copyright © 1990-2012 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

 

 

Amazon Kindle Fire HD

Google Nexus 7

 

Introduction

The first generation of 7 inch Tablets that launched in November of 2011 established an important new category with mass consumer appeal. They have only about half the screen area of 10 inch Tablets, so they fill the large gap between 4 inch Smartphones and the large Tablets. But in addition to being a lot smaller and more portable than their 10 inch cousins, they were considerably less expensive, with the original Amazon Kindle Fire pioneering a $199 price that was considerably less than half the cost of existing Tablets. With that size and price point they couldn’t simply be miniature 10 inch Tablets. In particular, they can’t provide all of the same hardware and functionality due to both size and cost constraints. This was incredibly challenging, so the first generation displays came in near the bottom in Brightness, Resolution, Color Gamut, Contrast, Calibration accuracy, Screen Reflectance, and performance under high Ambient Lighting (to name just a few). Still consumers bought them in droves, so millions were sold – and that always guarantees a sequel…

 

Now in less than a year a second generation of 7 inch Tablets has arrived – the Google Nexus 7 launched in July and the Amazon Kindle Fire HD in September. There are many other manufacturers making Tablets but these are the only models seeing significant demand. As we’ll see, in this short period of time these mini Tablets have evolved into first tier products with excellent displays that out perform most full size higher priced Tablets. It shows how demand can drive the state-of-the art very quickly. And they have become so successful that Apple can no longer ignore them – so an iPad Mini is rumored to be coming in October – we’ll analyze what is known about them so far.

 

The Shoot-Out

To compare the performance of the new Kindle Fire HD and Google Nexus 7 we ran our in-depth series of Mobile Display Technology Shoot-Out tests on them, together with the new iPad and the iPad 2 to see how they all compare. We take display quality very seriously and provide in-depth objective analysis side-by-side comparisons based on detailed laboratory measurements and extensive viewing tests with both test patterns and test images. For comparisons with earlier “popular” Tablets see our 10 Inch Tablet Display Technology Shoot-Out and for the comparisons with the original Amazon Kindle Fire and Barnes & Noble Nook Tablet see our First Generation IPS Tablet Display Technology Shoot-Out.

 

Results Highlights

In this Results section we provide Highlights of the comprehensive lab measurements and extensive side-by-side visual comparisons using test photos, test images and test patterns that are presented in later sections. The Comparison Table in the following section summarizes the lab measurements in the following categories:  Screen ReflectionsBrightness and ContrastColors and IntensitiesViewing AnglesDisplay Backlight Power ConsumptionRunning Time on Battery. You can also skip the Highlights and go directly to the Conclusions.

 

Comparison with iPads:

Our original plan for the Shoot-Out had been to compare the displays on these inexpensive $199 Tablets to the $399 iPad 2 – even that seemed rather unfair given the 2:1 price difference. But it didn’t take very long to see that the Kindle Fire HD handily beat the iPad 2 in terms of picture quality and accuracy, so we decided to upgrade the level of the Shoot-Out and instead use the new iPad for the detailed display comparisons below. While the display on the Kindle Fire HD does not beat the new iPad, it comes in a relatively close second, and it even outperforms the new iPad in a number of categories. That is a significant result all by itself – it shows how quickly the competition and state-of-the-art is changing because the new iPad has one of the most accurate displays in a consumer product that we have ever tested, including high-end HDTVs. The display on the Nexus 7 did not perform as well as the Kindle Fire HD as explained in detail below. We also discuss below how the (rumored) upcoming iPad Mini is likely to fit in with these Tablets.

 

Sharpness:

The display’s image sharpness depends on the pixel Resolution, while the visual sharpness depends on the Pixels Per Inch PPI and the Viewing Distance (as well as how good your vision is compared to 20/20 Vision). The Kindle Fire HD and Nexus 7 have 1280x800 pixel displays, which exceeds the resolution needed for viewing standard High Definition 1280x720 video content, one of their principal marketing goals. They have 30 percent more pixels than the iPad 2 but only one third of the number on the new iPad, which can display Full HD 1920x1080 content. For most photo and video content it is hard to visually distinguish HD 1280x720 from Full HD 1920x1080 because most photo and video images are inherently fuzzy, with the sharpest image detail spread over multiple pixels.

 

High visual sharpness is necessary for rendering fine text and graphics without pixelation and other visual artifacts. With 216 PPI the Kindle Fire HD and Nexus 7 are significantly better than the 132 PPI for the iPad 2, but well below the 264 PPI for the new iPad. The viewing distance where the Kindle Fire HD and Nexus 7 become what Apple calls a “Retina Display” is 15.9 inches – beyond that viewing distance people with 20/20 Vision cannot resolve the pixels so the display appears perfectly sharp. For viewing distances less than 15.9 inches the pixels can be resolved by the eye, but anti-aliasing will reduce their visibility. Since the viewing distance for 7 inch Tablets is around 12 inches their displays are not quite “Retina Displays” but they are still very sharp and close to the visual resolution limit for most people (who also don’t have 20/20 Vision).

 

Color Gamut and Color Accuracy:

While the display PPI and pixel Resolution seem to get most of the attention, it is the display’s Color Gamut together with the Factory Display Calibration (below) that play the most important role in determining the Wow factor and true picture quality and color accuracy of a display. The Color Gamut is the range of colors that a display can produce. If you want to see accurate colors in photos, videos, and all standard consumer content the display needs to closely match the Standard Color Gamut that was used to produce the content, which is called sRGB / Rec.709. Most of the first generation LCD Tablets have Color Gamuts around 60 percent of the Standard Gamut, which produces somewhat subdued colors. The original Kindle Fire and Nook Color Tablets have 55 percent, the iPad 2 has 61 percent, but the new iPad pulled way ahead and has a virtually perfect 99 percent of the Standard Color Gamut. The new Kindle Fire HD and the Nexus 7 both deliver an impressive 86 percent Standard Color Gamut, a major improvement over almost all previous generation Tablets (and Smartphones).

 

While the Kindle Fire HD and Nexus 7 both have an 86 percent Color Gamut, they are actually rather different as discussed in detail below. While the Nexus 7 has a very nice saturated Red that is close to the new iPad Red, its Greens and Yellows are less saturated than even the iPad 2, which is a significant step backward. On the other hand, the Kindle Fire HD has Greens and Yellows that are slightly more saturated than the new iPad. These were easy to see during the Viewing Tests. Just as important as the Color Gamut is the Factory Display Calibration, which can ruin a excellent display if done improperly…

 

Factory Display Calibration:

The raw LCD panel hardware first needs to be adjusted and calibrated at the factory with specialized firmware and software data that are downloaded into the device in order for the display to produce a usable image – let alone an accurate and beautiful one. This is actually a science but most manufacturers seem to treat it as if it were a modern art form, so few Tablets, Smartphones, and even HDTVs produce accurate high quality images. Apple does a virtually perfect Factory Calibration for the new iPad, and Amazon has done an excellent Factory Calibration for the Kindle Fire HD. It is probably more accurate with better color than any display you own.

 

On the other hand, the Factory Display Calibration on the Nexus 7 was severely botched, which significantly degrades its picture quality. In spite of its good Color Gamut, colors and contrast are washed out due to a compressed, convex, and irregular Intensity Scale (sometimes called the Gray Scale). Bright images look like over exposed photographs. We have discussed this in more detail in this Display News article – also see Figure 3 below for more information.

 

Nexus 7 Bugs:

The Factory Display Calibration problem mentioned above for the Nexus 7 display qualifies as a bug because it is a software or firmware problem rather than an inherent hardware display issue. Depending on the display firmware this may or may not be correctable with a software update.

 

The Nexus 7 has another serious display bug: During testing we found that the Brightness (Luminance) of the display decreases erratically by up to 15 percent. This is large enough to be occasionally noticeable and bring the Nexus 7 Maximum Brightness down to almost 300 cd/m2, which we classify as Poor for Maximum Brightness. We borrowed and tested a second Nexus 7 unit and found identical behavior – so the effect is unlikely to be due to a defective unit. In fact, we discovered it to be another software bug. On the Nexus 7 the measured Luminance for a given image doesn’t change over time – but it varies based on the user interactivity pattern and history. For example, flipping to other images and then returning back to the original image often results in a change in Luminance. This indicates that it is caused by a software bug of some sort, possibly related to a faulty implementation of Dynamic Backlight or Dynamic Contrast. This erratic behavior introduces some uncertainties into the Nexus 7 measurements below. We believe the listed values are correct as a result of many repeated measurements. It is likely that this particular display bug can be fixed by Google with a software update.

 

Viewing Tests:

Using our extensive library of challenging test and calibration photos, we compared the Tablets to a calibrated professional studio monitor, and to the new iPad, which has a virtually perfect Factory Calibration and Color Gamut. As expected from the Lab measurements, the Kindle Fire HD produced beautiful picture quality, much better than the iPad 2 and almost as good as the new iPad. The only visually notable issue was that very deep reds, like in a fire engine, were not as vibrant and have a slight shift towards orange.

 

Images on the Nexus 7 were noticeably washed out in both color and image contrast – especially bright images. For example, this was rather noticeable in photographs of faces, which are often the center of attention and brightly lit, and the eye is especially critical when faces are rendered improperly. Another important issue was that Greens and Yellows were especially weak and under saturated, even much more than the iPad 2, which has a much smaller Color Gamut but a more saturated Green primary.

 

Screen Reflectance:

The screens on almost all Tablets and Smartphones are mirrors good enough to use for personal grooming. Even in moderate ambient lighting the contrast and colors can noticeably degrade from ambient light reflected by the screen, especially objects like your face and any bright lighting behind you. So low Reflectance is very important in determining real picture quality. The lower the better… This article shows how screen images degrade in bright Ambient Light.

 

Screen Reflectance on the iPad 2 is 8.7 percent and on the new iPad it is 7.7 percent. However, on the Nexus 7 the Reflectance is an impressive much lower 5.9 percent, while on the Kindle Fire HD it is 6.4 percent – both are significant improvements over the iPads. For comparison, the iPad 2 reflects 47 percent more ambient light than the Nexus 7 and 36 percent more than the Kindle Fire HD. Screen visibility and readability in high Ambient Light depends on both the Maximum Brightness and Screen Reflectance. The Kindle Fire HD has the highest measured Contrast Rating for High Ambient Light of any Tablet that we have tested in our entire Shoot-Out series, and the Nexus 7 is a close second. Both are much better than either the iPad 2 or the new iPad.

 

The Rumored iPad Mini?

There are credible rumors that sometime in October Apple will announce an iPad Mini with a 7.85 inch 160 PPI screen and solution of 1024x768 pixels. Given that Apple generally does a good job with their displays, how is it likely to compare and compete with these existing Tablets?

 

Color Gamut: It’s very likely that the iPad Mini will have a 100 percent Color Gamut like the new iPad , which is 14 percent greater than the Kindle Fire HD and Nexus 7. Pixels Per Inch: The Kindle Fire HD and Nexus 7 have 216 PPI, considerably greater than the predicted 160 PPI for the iPad Mini or the 132 PPI for the iPad 2, but considerably less than the 264 PPI for the new iPad. Screen Resolution: The Kindle Fire HD and Nexus 7 have1280x800 resolution with a 16:10 Aspect Ratio, considerably greater than the iPad Mini’s predicted 1024x768 with a 4:3 Aspect Ratio. Video Resolution: When looking at standard 16:9 HDTV widescreen content, the Kindle Fire HD and Nexus 7 deliver Standard HD 1280x720 Resolution, considerably greater than the 1024x576 Resolution predicted for the iPad Mini. Screen Area: The iPad Mini is predicted to have an area that is 34 percent larger than the Kindle Fire HD and Nexus 7. However, for 16:9 content the area is only 6 percent larger.

 

An Updated Shoot-Out:

When the iPad Mini becomes available we will do another complete 7 inch Tablet Shoot-Out with the iPad Mini instead of the new iPad. We’ll also check to see if Google has corrected the Calibration and Brightness problems noted above with a software update.

 

 

Conclusion:   An Impressive Second Generation…

The first generation of 7 inch Tablets that launched in 2011 established an important new category with mass consumer appeal. This second generation of 7 inch Tablets has resulted in impressive improvements in display quality, now rivaling the top performing and most expensive large format Tablets, including the new iPad. The 7 inch Tablets have only about half the screen area of 10 inch Tablets, so they are much easier to carry around and fill the large gap between 4 inch Smartphones and the large Tablets. Amazon and Google are also positioning them to sell video content, subscriptions, and consumer goods. This is the justification for being able to sell them at the incredibly low $199 price point, with close to zero margin. The displays need to produce beautiful picture quality in order to encourage consumers to purchase lots of content.

 

The display on the Kindle Fire was the decisive winner of these two leading 7 inch Tablets. It is much better than the iPad 2 and almost as good as the new iPad in overall picture quality and color accuracy. While the new iPad’s 264 PPI screen is significantly sharper for reading text and viewing finely detailed computer graphics, the Kindle Fire HD’s 216 PPI screen is still very sharp and its 1280x800 screen exceeds the resolution needed for viewing standard High Definition 1280x720 video content, one of its principal marketing goals. Like the new iPad, the Kindle Fire HD has better picture quality and color accuracy than most HDTVs, laptops, and monitors, so it could wind up being your most accurate display for viewing photos, videos and web content. Mobile displays are often viewed under reasonably high Ambient Lighting. The Kindle Fire HD has the highest measured Contrast Rating for High Ambient Light of any Tablet that we have tested in our Shoot-Out series, which is impressive.

 

The Nexus 7 actually has an LCD display that is similar in performance to the Kindle Fire HD, but a poor (and sloppy) Factory Calibration has degraded its native panel performance. Depending on the display firmware this may or may not be correctable with a software update. A second problem is a bug that causes a 15 percent erratic variation in screen Brightness, sometimes bringing the Nexus 7 Maximum Brightness down to almost 300 cd/m2, which we classify as Poor for Maximum Brightness. It is likely that this particular display bug can be fixed by Google with a software update. On the other hand, the Kindle Fire HD has a (stable) Maximum Brightness of 434 cd/m2 that is much brighter than the Nexus 7 and among the Brightest Tablets we have tested. If both Nexus 7 problems are fixed with a software update, then the Nexus 7 display will be much closer in performance to the Kindle Fire HD. But in addition to these, the Nexus 7 has a Green primary that is much less saturated than even the iPad 2, which is quite noticeable and a step backward. This also significantly lowers the saturation of Yellows that lie between Green and Red. This can’t be fixed in software, but even so, the Nexus 7 could still become a very good display if the other display software and firmware issues are fixed.

 

Of course, the big question is how the rumored iPad Mini will affect the 7 inch Tablet category, and how will the Kindle Fire HD and Nexus 7 be impacted by its expected introduction in October? If the display predictions in our Rumored iPad Mini section above come true, then there are enough pluses and minuses between them that they should all be able to coexist as far as display performance and picture quality are concerned.

 

While these Tablet displays are all very good, there is still plenty of Room for Improvement. See the new iPad Shoot-Out Conclusion for a discussion of the many improvements that are needed for the next generation of Tablet displays.

 

 

DisplayMate Display Optimization Technology

All Tablet and Smartphone displays can be significantly improved using DisplayMate’s advanced scientific analysis and mathematical display modeling and optimization of the display hardware, factory calibration, and driver parameters. We help manufacturers with expert display procurement and quality control so they don’t make mistakes similar to those that are exposed in our Display Technology Shoot-Out series. We can also improve the performance of any specified set of display parameters. This article is a lite version of our intensive scientific analysis – before the benefits of our DisplayMate Display Optimization Technology, which can correct or improve all of these issues. If you are a display or product manufacturer and want to significantly improve display performance for a competitive advantage then Contact DisplayMate Technologies.

 

Amazon Kindle Fire HD

Google Nexus 7

 

Display Shoot-Out Comparison Table

Below we compare the displays on the Amazon Kindle Fire HD and Google Nexus 7 with the new iPad based on objective measurement data and criteria. Note that the tested Tablets were purchased independently by DisplayMate Technologies through standard retail channels.

 

For additional background and information see the iPad Display Technology Shoot-Out article that compares the iPad 2 and the new iPad.

When the iPad Mini is launched we will add it to the 7 inch Tablet Shoot-Out.

 

Categories

Amazon

Kindle Fire HD

Google

Nexus 7

Apple

new iPad

Comments

Display Technology

7.0 inch IPS LCD

7.0 inch IPS LCD

9.7 inch IPS LCD

Liquid Crystal Display

In Plane Switching

Screen Shape

16:10 = 1.60

Aspect Ratio

16:10 = 1.60

Aspect Ratio

4:3  =  1.33

Aspect Ratio

The iPad screen has the same shape as 8.5x11 paper.

Screen Area

22.0 Square Inches

22.0 Square Inches

45.2 Square Inches

A better measure of size than the diagonal length.

Relative Screen Area

49 percent

49 percent

100 percent

Screen Area relative to the new iPad.

Display Resolution

1280 x 800 pixels

1280 x 800 pixels

2048 x 1536 pixels

The more Pixels and Sub-Pixels the better.

Active Display Area

1280 x 800 pixels

1280 x 736 pixels

2048 x 1536 pixels

The Nexus 7 reserves 64 pixels for a navigation bar.

Pixels Per Inch

216 ppi

Very Good

216 ppi

Very Good

264 ppi

Excellent

At 12 inches from the screen 20/20 vision is 286 ppi.

See this on the visual acuity for a true Retina Display

20/20 Vision Retina Display

down to this Viewing Distance

20/20 “Retina Display”

to 15.9 inches Viewing

20/20 “Retina Display”

to 15.9 inches Viewing

20/20 “Retina Display”

to 13.0 inches Viewing

For 20/20 Vision the minimum Viewing Distance

where the screen appears perfectly sharp to the eye.

Gallery / Photo Viewer Color Depth

Full 24-bit color

No Dithering Visible

256 Intensity Levels

Dithered 24-bit color

False Contouring

Full 24-bit color

No Dithering Visible

256 Intensity Levels

Most Android Tablets and Smartphones still have some

form of 16-bit color depth in the Gallery Photo Viewer

 

Kindle Fire HD

Nexus 7

new iPad

 

 

Overall Assessments

This section summarizes the results of all of the extensive Lab measurements and viewing tests performed on all of the displays.

 

Viewing Tests

Very Good Images

Photos and Videos

have accurate color

and accurate contrast

Good Images

Photos and Videos

have washed out

color and contrast

Very Good Images

Photos and Videos

have accurate color

and accurate contrast

The Viewing Tests examined the accuracy of

photographic images by comparing the displays

to a calibrated studio monitor and HDTV.

Variation with Viewing Angle

Small Color Shifts

with Viewing Angle

 

Large Brightness Shift

with Viewing Angle

Small Color Shifts

with Viewing Angle

 

Large Brightness Shift

with Viewing Angle

Small Color Shifts

with Viewing Angle

 

Large Brightness Shift

with Viewing Angle

IPS LCDs have Small Color Shifts.

TN LCDs have Large Color Shifts.

 

All LCDs have Large Brightness Shifts

Viewing the Screen with

Polarized Sunglasses

Extinction in

Landscape

 

View in Portrait

Extinction in

Landscape

 

View in Portrait

Extinction in

Portrait

 

View in Landscape

Polarized Sunglasses are increasingly popular,

which often makes the screen invisible black for

certain orientations.

Overall Display Assessment

Lab Tests and Viewing Tests

Very Good Display

Very Good Calibration

Good Display has

Poor Calibration

Washed Out Images

Bugs that need Fixing

Excellent Display

Excellent Calibration

The Nexus 7 display can be significantly improved

if Google fixes the two software and firmware bugs

that we identified.

Current Overall Display Grade

A–

 B–

A

If Google fixes the two software and firmware bugs

we identified the Nexus 7 Display Grade will go up

to B+ due to the Color Gamut issues we identified.

 

Kindle Fire HD

Nexus 7

new iPad

 

 

 

 

Screen Reflections

Figure 1.  Screen Reflection Photos

Click to Enlarge

All of these screens are large mirrors good enough to use for personal grooming – but it’s actually a very bad feature…

We measured the light reflected from all directions and also direct mirror (specular) reflections, which are much more

distracting and cause more eye strain. The 10 – 15 percent reflections can make the screen much harder to read even

in moderate ambient light levels, requiring ever higher brightness settings that waste precious battery power. Hopefully

manufacturers will reduce the mirror reflections with anti-reflection coatings and haze surface finishes.

 

The Kindle Fire HD and Nexus 7 significantly outperform the new iPad with much lower Reflectance.

The new iPad reflects 31 percent more ambient light than the Nexus 7 and 20 percent more than the Kindle Fire HD.

Average Screen Reflection

Light From All Directions

Reflects 6.4 percent

Very Good

Reflects 5.9 percent

Very Good

Reflects 7.7 percent

Very Good

Measured using an Integrating Hemisphere.

The best value we have measured is 4.4 percent

and the current worst is 14.8 percent.

Mirror Reflections

Percentage of Light Reflected

7.6 percent

Very Good

7.2 percent

Very Good

9.9 percent

Good

These are the most annoying types of reflections.

Measured using a narrow collimated pencil beam of

light reflected off the screen.

 

Kindle Fire HD

Nexus 7

new iPad

 

 

Brightness and Contrast

The Contrast Ratio is the specification that gets the most attention, but it only applies for low ambient light, which is seldom

the case for mobile displays. Much more important is the Contrast Rating, which indicates how easy it is to read the screen

under high ambient lighting and depends on both the Maximum Brightness and the Screen Reflectance.

 

The Nexus 7 Maximum Brightness is lower than many Tablets plus it has a Bug that causes the Brightness to decrease

erratically by up to 15 percent down to almost 300 cd/m2, which we classify as Poor for Maximum Brightness.

See Nexus 7 Bugs under Highlights for more details.

Measured Maximum Brightness

is the Peak Luminance for White

Brightness 434 cd/m2

Very Good

Brightness 372 cd/m2

Good

Brightness 421 cd/m2

Very Good

Maximum Brightness is very important for mobile

because of the typically high ambient light levels.

Black Level

at Maximum Brightness

Black is 0.51 cd/m2

Very Good for Mobile

Black is 0.40 cd/m2

Very Good for Mobile

Black 0.48 cd/m2

Very Good for Mobile

Black brightness is important for low ambient light,

which is seldom the case for mobile devices.

Contrast Ratio

Relevant for Low Ambient Light

851

Very Good for Mobile

930

Very Good for Mobile

877

Very Good for Mobile

Only relevant for low ambient light,

which is seldom the case for mobile devices.

Defined as Maximum Brightness / Black Brightness.

Contrast Rating

for High Ambient Light

68

Very Good

63

Very Good

55

Good

Defined as Maximum Brightness / Average Reflectance.

Screen Readability in Bright Light

Very Good    A–

Very Good    A–

Good    B+

Indicates how easy it is to read the screen

under high ambient lighting. Very Important!

See High Ambient Light Screen Shots

 

Kindle Fire HD

Nexus 7

new iPad

 

 

 

 

Colors and Intensities    

Figure 2.  Color Gamuts

Click to Enlarge

Figure 3.  Intensity Scales

Click to Enlarge

The Color Gamut, Intensity Scale, and White Point determine the quality and accuracy of all displayed images and all

the image colors. Bigger is definitely Not Better because the display needs to match all the standards that were used

when the content was produced. For LCDs a wider Color Gamut reduces the power efficiency and the Intensity Scale

affects both image brightness and color mixture accuracy.

 

The Nexus 7 has a major problem with its Intensity Scale due to a poor Factory Calibration. We have discussed this

in more detail in this Display News article – also see Figure 3 for more information.

Some important issues regarding the Color Gamut are explained in Figure 2.

White Color Temperature

6,380 degrees Kelvin

Close to Standard

6,708 degrees Kelvin

Close to Standard

7,085 degrees Kelvin

Somewhat Too Blue

D6500 is the standard color of White for most content

and necessary for accurate color reproduction.

Color Gamut

See Figure 2

Very Good

86 percent of Std

See Figure 2

Very Good

86 percent of Std

See Figure 2

Excellent

99 percent of Std

See Figure 2

sRGB / Rec.709 is the color standard for most

content and needed for accurate color reproduction.

Note that Too Large a Color Gamut is visually

worse than Too Small.

Dynamic Contrast or Backlight

None

Excellent

Below 10 percent APL

Very Good

None

Excellent

Many manufacturers manipulate the Intensity Scale

and Backlight based on image content. That results

in inaccurate colors and images.

Intensity Scale and Image Contrast

See Figure 3

Very Smooth

Contrast is Excellent

See Figure 3

Irregular and Convex

Saturation and Clipping

See Figure 3

Very Smooth

Contrast is Perfect

See Figure 3

The Intensity Scale controls image contrast needed

for accurate image reproduction. See Figure 3

Gamma for the Intensity Scale

Larger means more Image Contrast

See Figure 3

Good 2.16

Gamma is Excellent

1.70  to  2.44

Gamma is Poor

Convex

Highly Variable

Outstanding 2.20

Gamma is Perfect

Gamma is the slope of the Intensity Scale.

Gamma of 2.20 is the standard and needed for

accurate image reproduction. See Figure 3

 

Kindle Fire HD

Nexus 7

new iPad

 

 

Viewing Angles

The variation of Brightness, Contrast, and Color with viewing angle is especially important for Tablets because of

their large screen and multiple viewers. The typical manufacturer 176+ degree specification for LCD Viewing Angle

is nonsense because that is where the Contrast Ratio falls to a miniscule 10. For most LCDs there are substantial

degradations at less than ±30 degrees, which is not an atypical viewing angle for Tablets. IPS LCDs generally do well.

 

Note that the Viewing Angle performance is also very important for a single viewer because the Viewing Angle

varies based on how the Tablet is held, and the angle can be very large if the Tablet is resting on a table or desk.

 

All of these IPS Tablets perform very well and have very similar Viewing Angle performance.

Brightness Decrease

at a 30 degree Viewing Angle

52 percent Decrease

Falls to 208 cd/m2

 

Very Large Decrease

53 percent Decrease

Falls to 175 cd/m2

 

Very Large Decrease

57 percent Decrease

Falls to 182 cd/m2

 

Very Large Decrease

Most screens become less bright when tilted.

 

LCD brightness variation is generally very large.

Contrast Ratio

at a 30 degree Viewing Angle

602

Very Good for Mobile

662

Very Good for Mobile

526

Very Good for Mobile

A measure of screen readability when the screen

is tilted under low ambient lighting.

Primary Color Shifts

at a 30 degree Viewing Angle

Small Color Shift

Δ(u’v’) = 0.0047

1.2 times JNCD

Small Color Shift

Δ(u’v’) = 0.045

1.1 times JNCD

Small Color Shift

Δ(u’v’) = 0.0046

1.2 times JNCD

JNCD is a Just Noticeable Color Difference.

IPS LCDs have smaller color shifts with angle.

Color Shifts for Color Mixtures

at a 30 degree Viewing Angle

Reference Brown (255, 128, 0)

Small Color Shift

Δ(u’v’) = 0.0069

1.7 times JNCD

Small Color Shift

Δ(u’v’) = 0.0068

1.7 times JNCD

Small Color Shift

Δ(u’v’) = 0.0073

1.8 times JNCD

JNCD is a Just Noticeable Color Difference.

Color Shifts for non-IPS LCDs are about 10 JNCD.

 

Reference Brown is a good indicator of color shifts

with angle because of unequal drive levels and

roughly equal luminance contributions from

Red and Green.

 

Kindle Fire HD

Nexus 7

new iPad

 

 

Display Backlight Power Consumption

Figure 4.  LED Backlight Spectrum

Click to Enlarge

  

The Display Backlight power does not include the power used by the LCD itself or by the display electronics.

Since the displays have different screen sizes and maximum brightness, the values were also scaled to the

same screen brightness (Luminance) and screen area in order to compare their relative Power Efficiencies.

 

The Nexus 7 is 24 percent more Power Efficient than the Kindle Fire HD and has double the Efficiency of the new iPad.

Display Backlight Power

at Maximum Brightness

2.1 watts

1.4 watts

7.0 watts

Lower power consumption is important for energy

efficiency and improving running time on battery.

Display Backlight Power Efficiency

same Peak Luminance 434 cd/m2

same 7 inch screen size area

2.1 watts

1.7 watts

3.5 watts

This compares the Relative Power Efficiency

by looking at the same screen brightness and

screen area.

 

Kindle Fire HD

Nexus 7

new iPad

 

 

Running Time on Battery

The running time on battery was determined with the Brightness sliders at Maximum, in Airplane Mode,

with no running applications, and with Auto Brightness turned off.

 

Note that Auto Brightness can have a considerable impact on running time but we found abysmal performance for

both the iPhone and Android Smartphones in our BrightnessGate analysis of Ambient Light Sensors and Automatic

Brightness. They all need a more convenient Manual Brightness Control as described in the BrightnessGate article.

 

The Nexus 7 has the longest Running Time at Maximum Brightness for any Tablet we have tested.

Running Time

At the Maximum Brightness Setting

6.6 hours

9.1 hours

5.8 hours

Display always On at the Maximum setting with

Airplane Mode and no running applications.

Categories

Kindle Fire HD

Nexus 7

new iPad

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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

All Tablet and Smartphone displays can be significantly improved using DisplayMate’s advanced scientific analysis and mathematical display modeling and optimization of the display hardware, factory calibration, and driver parameters. We help manufacturers with expert display procurement and quality control so they don’t make mistakes similar to those that are exposed in our Display Technology Shoot-Out series. We can also improve the performance of any specified set of display parameters. This article is a lite version of our intensive scientific analysis – before the benefits of our DisplayMate Display Optimization Technology, which can correct or improve all of these issues. If you are a display or product manufacturer and want to significantly improve display performance for a competitive advantage then Contact DisplayMate Technologies.

 

About DisplayMate Technologies

DisplayMate Technologies specializes in proprietary sophisticated 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 Tablet 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. 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. 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 to turn your display into a spectacular one to surpass your competition then Contact DisplayMate Technologies to learn more.

 

 

Article Links:  new iPad and iPad 2 Display Technology Shoot-Out

Article Links:  10 Inch Tablet Display Technology Shoot-Out

 

Article Links:  Tablet Displays Under High Ambient Lighting Shoot-Out

Article Links:  Automatic Brightness Controls and Light Sensors

 

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

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

 

 

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