Full HD Flagship Smartphone Display Technology Shoot-Out
HTC One – Huawei Ascend D2
– Sony Xperia Z
Dr. Raymond M. Soneira
President, DisplayMate Technologies Corporation
Copyright © 1990-2013 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
A new generation of Smartphones with Full High Definition 1920x1080
displays have arrived, the same as your living room HDTV, but with a 5 inch
screen size – that is very impressive! But, how good are these new displays, do
you really need all of that sharpness and resolution, and will you be able to
actually see the difference? Also, how do they compare with the Apple iPhone 5
and Samsung Galaxy S4? We’ll cover these issues and much more, with in-depth
comprehensive display tests and analysis that you will find nowhere else.
With the iPhone 4 Retina Display, Apple pioneered the previous
generation of Smartphone displays in 2010. This time the pioneers are all
Android devices, with the iPhone still not even at the basic HD resolution of
1280x720. But there are rumors of higher resolutions and larger Apple
Smartphones on the way, possibly even in the Phablet size class – we’ll see…
In this article we’ll examine three Flagship Full HD top-of-the-line
Smartphones: the HTC One, Huawei Ascend D2, and the Sony Xperia Z, all with 5.0
inch or smaller screens. The LG Optimus G Pro has an excellent Full HD display
that we have tested (for SID Information Display magazine), but it’s currently
available only in a larger 5.5 inch size – a smaller 5.0 inch model is coming,
which we plan on including when it becomes available. While Huawei is better
known as a manufacturer of low cost Smartphones, their Ascend D2 is aimed at
the premium top tier, and as you’ll see below, they managed to hit a home run
with the display the first time at bat – that’s also very impressive!
The Shoot-Out
To examine the performance of these Flagship Full HD
Smartphone displays we ran our in-depth series of Mobile Display Technology
Shoot-Out Lab tests. We take display quality very seriously and provide
in-depth objective analysis and side-by-side comparisons based on detailed
laboratory measurements and extensive viewing tests with both test patterns and
test images. To see how far Smartphones have progressed in just three years see
our 2010
Smartphone Display Shoot-Out, and for a real history lesson see our
original 2006
Smartphone Display Shoot-Out.
Results Highlights
In this Results section we provide Highlights of the
comprehensive Lab tests, 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
Reflections, Brightness
and Contrast, Colors
and Intensities, Viewing
Angles, Display
Power Consumption, Running
Time on Battery. You can also skip these Highlights and go directly to the Conclusions.
Can You Actually See the Enhanced Full HD Sharpness and
Resolution?
Apple started a major
revolution in display marketing by introducing their “Retina Display” with 326
Pixels Per Inch (PPI) on the iPhone 4 in 2010. While not equivalent to the
resolution of the human retina, people with 20/20 Vision cannot resolve the
individual pixels when the display is held at normal viewing distances of 10.5
inches or more. This started a PPI and Mega Pixel war similar to what happened
with Smartphone digital cameras, which is still an ongoing wild goose chase now
into the stratosphere… Hopefully the same thing won’t happen with mobile
displays. The real question is how high do we need to go before reaching a
practical visual PPI limit?
True Retina Displays: As I have
pointed out before, the effective resolution of the human retina is much
higher than Apple’s Retina Display, and corresponds to somewhere around 600 PPI
at a 10 inch viewing distance, which is the limit for the best human vision,
around 20/10. That is well above the highest 468 PPI display that we test here,
so the Full HD higher resolution and sharpness should be visually apparent. On
the other hand, very few people have that level of 20/10 visual acuity. In
fact, a fair fraction of the adult population does not have corrected (near)
vision even to 20/20. Furthermore, ambient light decreases visual acuity
because the reflected light glare from the screen reduces image contrast – and
Smartphones are almost never viewed in the dark. So perhaps the extra sharpness
won’t be apparent for many situations, especially casual viewing…
Enhanced Acuity: But if you want (or need) to take advantage of
that extra display sharpness and resolution, you can. If you study and stare at
the image on the screen, move it closer, or move it around, you’ll be able to
make out considerably more fine image detail because you are building an
integrated visual image map in the brain. So, when you are looking at an image
with finely detailed graphics and small text, most people with reasonably good
vision will be able to make out and appreciate the extra sharpness and image
detail if they take the time to do so.
Photos and Videos: Unlike computer generated text and graphics that
have precise pixel arrangements, photographic images are inherently fuzzy
because the image detail is spread over multiple pixels, so you are less likely
to detect a sharpness difference over basic 1280x720 HD, especially with jpeg
images, which are all digitally compressed. That’s for still photos, but movies
and videos have images that are continually changing so a fair amount of image
detail is often visually lost due to its transitory nature (plus digital
compression). So for photos, movies and videos the extra sharpness and
resolution will be less apparent…
From the above
discussion, there are lots of good and technically sound reasons for moving up
to Full HD in a 5 inch Smartphone display. People with reasonably good vision
will be able to see and appreciate the higher resolution, additional sharpness
and image detail that it provides.
Overall Display Performance
In our Lab tests and
measurements the three Smartphone displays, for the most part, delivered
comparable and very good to excellent performance, including Brightness,
Contrast Ratio (low ambient light), Contrast Rating for High Ambient Light,
Reflectance, White Point, and Display Power Efficiency, which are analyzed in
the Comparison
Table. Below are a number of major issues where the displays performed very
differently.
Color Gamut
In
order to produce accurate image colors on-screen the displays need to match the
Standard Color Gamut that is used to create virtually all current consumer
content, which is named sRGB / Rec.709 (not the occasionally mentioned NTSC
Gamut, which was defined in 1953 and has been obsolete for over 30 years). The
Standard Gamut encompasses digital camera, HDTV, Internet, and computer content,
including virtually all photos and videos. Note that standard consumer content
does not include colors outside of the Standard sRGB / Rec.709 Gamut, so a
display with a wider Color Gamut cannot show colors that are not in the
original, and only produce inaccurate exaggerated on-screen colors.
Most
LCDs until recently delivered only 55 to 65 percent of the sRGB / Rec.709 Color
Gamut, but many newer Smartphones are producing close to 100 percent of the
Standard Gamut, including the HTC One and Huawei Ascend D2 tested here.
However, the Sony Xperia Z has a somewhat too large Color Gamut of 115 percent,
which contributes to its many problems with color accuracy.
Viewing Angle Issues
The
image brightness, contrast, and colors can vary significantly when the screen
Viewing Angle changes by even ±30 degrees, which is quite common for
Smartphones because it depends on how you hold it in your hand (with varying
pitch). The angle can be even larger if the Smartphone is resting on a table or
desk.
While all LCDs
show large decreases in brightness with Viewing Angle (generally over 50
percent at ±30 degrees), it is now unusual for high-end LCDs with In Plane
Switching (IPS) or similar technology to show substantial color and contrast
shifts with Viewing Angle, which were shockingly large on the Sony Xperia Z.
The problem is incredibly large increases in the background Black Level with
small changes in Viewing Angle, which significantly washes out and degrades the
image contrast and colors. This could be an LCD technology issue or possibly
due to the use of a low grade polarizer in the panel. To double check this, we
tested another similar model, the Xperia ZL, and it showed the same substantial
degradation with Viewing Angle. On the other hand, both the HTC One and Huawei
Ascend D2 have excellent viewing angle performance, with no visible color
shifts. This Figure
with screen shots illustrates the Viewing Angle performance for the three
tested Smartphone displays. Measurement details are provided in the Viewing
Angles Table below.
Color Accuracy and Calibration
Picture quality and Color
Accuracy are especially important for these Full HD 5 inch displays because
they are multimedia devices designed for viewing photos, videos, movies, HDTV
and internet content. It takes careful display hardware design and careful
factory calibration to produce top notch picture quality and color accuracy.
Some manufacturers attempt to make their displays standout with image
processing “enhancements” that exaggerate the colors and image contrast. The
result is almost always distorted and over saturated colors and contrast. It is
almost impossible to get the image processing “enhancements” to work well
because of the incredible range and variety of images that can be displayed.
The Huawei Ascend D2 avoids this sort of image processing and simply relies on
standard accurate display calibration. Unfortunately, both the HTC One and Sony
Xperia Z use excessive processing that results in distorted and over saturated
colors and contrast.
Viewing Tests
Not surprisingly, all three displays were extremely
sharp, and had bright screens with good image contrast, but only at zero
degrees Viewing Angle for the Sony Xperia Z, which has large color and image
contrast shifts with Viewing Angle as described above. Where all three displays
diverged significantly was in their Color Accuracy and Calibration due to
excessive image and color processing, which some manufacturers do intentionally
to try to make their displays stand out. But the end result almost always
produces distorted and over saturated colors and contrast as described above.
In our extensive Viewing Tests with a large set of challenging test photos and
test images the three Smartphone displays were incredibly different as we
compared them side-by-side to each other and to a number of accurate calibrated
displays. The Huawei Ascend D2 delivered every bit as good picture quality and
color accuracy as the iPhone 5 and Galaxy S4, but the HTC One had noticeably
and significantly inaccurate, distorted and over saturated colors and contrast.
The Sony Xperia Z was significantly worse with its “Bravia Engine” On – turning
it Off improved its picture quality a lot, but not enough.
It is surprisingly difficult to capture the magnitude of
the differences seen live using camera screen shots. We’ve often used the
following photo of a colorful barn door. This Figure with screen shots
illustrates the differences in Viewing Test performance for the three
Smartphone displays. When viewed live side-by-side the differences between the
displays appear much greater.
HTC One
While it has an excellent LCD panel (made by Sharp), HTC
has significantly degraded display performance by introducing unnecessary image
and color processing in a poorly implemented attempt at making the display
stand out. The result is distorted and over saturated colors and contrast. And
unlike Sony, HTC does not provide an option to turn this processing off, which
is a shame. Hopefully, such an option will become available in a future
software upgrade.
Huawei Ascend D2
With the Ascend D2 Huawei appears to have taken the same
successful solid approach for display performance as Apple. In our extensive
side-by-side viewing test comparisons the Ascend D2 was virtually
indistinguishable from the iPhone 5 and iPad Retina Display, two of the most
accurate and high quality mobile displays we have ever tested. The Huawei
Ascend D2 joins an elite group of Smartphones with world class displays.
Sony Xperia Z
The performance of the Sony Xperia Z flagship
top-of-the-line Smartphone can only be described as extremely disappointing.
First of all, the Xperia Z has awful viewing angle performance, which is common
for low-end low-technology displays, but is inexcusable in an expensive
flagship top-of-the-line product. Second, the “Bravia Engine” that they brag
enhances picture quality instead significantly degrades it, introducing
extremely gaudy, oversaturated and distorted colors – similar to what you’ll
see if you turn the Color Control on your HDTV all the way up to maximum. At
least they provide an option to turn the Bravia Engine Off, which improves
things a lot, but not enough.
Comparison with the iPhone 5 Display
The Apple iPhone 5 is now more than half way through its
product cycle, which is important to keep in mind for our comparison. However,
the primary differences come down to its much smaller Screen Size (4.0 versus
4.7 to 5.0 inches), much lower Pixel Resolution (1136x640 versus 1920x1080),
much lower total number of Pixels (0.7 versus 2.1 Mega Pixels), and much lower
Pixels Per Inch (326 versus 443 to 468). On the plus side, the iPhone 5 has a
much higher Peak Brightness (556 versus 421 to 491 cd/m2), a much
lower Screen Reflectance (4.5 versus 5.6 to 6.5 percent), a much higher
Contrast Rating for High Ambient Light (121 versus 65 to 88), and therefore
much better screen visibility in high ambient light. All are major plus and
minus differences.
But the most interesting and significant development is
that one of the Full HD Smartphones that we tested here, the Huawei Ascend D2,
delivers every bit as good a picture quality and color accuracy as the iPhone 5
(but at a much higher resolution and screen size). In fact, in side-by-side
viewing tests the two are almost indistinguishable because they both have
accurately calibrated displays, which makes it a tie in picture quality, unlike
the HTC One and Sony Xperia Z, which are one or two steps below.
Comparison with the
Galaxy S4 OLED Display
The Samsung Galaxy S4 is another important milestone
display that we tested in a recent Shoot-Out article.
Because OLED technology is significantly different from LCD technology there
are many subtle performance issues that are examined in that article. The two
most significant differences are: OLEDs provide perfect blacks but LCDs are
currently significantly brighter. However, the Galaxy S4 has a much lower
Screen Reflectance (4.4 versus 5.6 to 6.5 percent), and as a result, a somewhat
higher Contrast Rating for High Ambient Light (65 to 108 versus 65 to 88). The
Galaxy S4 also provides multiple Color Gamuts, including one that is very
accurate, another for professional photography, and a larger one that is better
in high ambient light. In terms of image sharpness, the Galaxy S4 also has Full
HD 1920x1080 resolution – but there is one important difference, the LCD
displays have 3 sub-pixels per pixel while the Galaxy S4 has a PenTile
structure with only 2 sub-pixels per pixel. However, the very high 312 to 443
Sub-Pixels Per Inch together with its advanced sub-pixel rendering still
results in a very visually sharp display. In the end, they each have their own
particular strengths and weaknesses, so for the time being, it remains a tie
between the high-end LCDs and OLEDs…
Conclusion: One Very Impressive Full HD
Smartphone Display…
It is amazing to hold a
beautiful Full HD 1920x1080 mobile computer display and HDTV in the palm of
your hand. But only one of the Smartphones tested here qualifies as a beautiful
display – the Huawei Ascend D2, because it delivers superior picture quality
with accurate colors and images. This Figure with screen
shots illustrates the major points we make in the Conclusion with the
measurement details in the Comparison
Table below.
With the Ascend D2 Huawei appears to have taken the same
successful solid approach for display performance as Apple. In our extensive
side-by-side viewing test comparisons the Ascend D2 was virtually
indistinguishable from the iPhone 5 and iPad Retina Display, two of the most
accurate and high quality mobile displays we have ever tested. The Huawei
Ascend D2 joins an elite group of Smartphones with world class displays. While
Huawei is better known as a manufacturer of low cost Smartphones, their Ascend
D2 is aimed at the premium top tier, so they managed to hit a home run with the
display the first time at bat. My suggestion for Huawei, please keep it up…
I was expecting a lot better from the HTC One. While it has an
excellent LCD panel (made by Sharp), HTC has significantly degraded display
performance by introducing unnecessary image and color processing in a poorly
implemented attempt at making the display stand out. The result is distorted
and over saturated colors and contrast. And unlike Sony, HTC doesn’t provide an
option to turn this processing off, which is a shame. Hopefully that will be an
option in a future software upgrade. My suggestion for HTC, forget the display
image processing tricks, which never work, and follow Apple and Huawei with
solid and straightforward accurate display calibration…
The performance of the Sony Xperia Z flagship top-of-the-line Smartphone can
only be described as extremely disappointing – even shocking, given that Sony
was once the best display manufacturer in the world, famous for their beautiful
and accurate picture quality – something they brag about on their Xperia Z web
page – but is very far from reality for the Xperia Z. First of all, the Xperia
Z has awful viewing angle performance, which is common for low-end
low-technology displays, but is inexcusable in an expensive flagship
top-of-the-line product. Second, the “Bravia Engine” that they brag enhances
picture quality instead significantly degrades it, introducing extremely gaudy,
oversaturated and distorted colors – similar to what you’ll see if you turn the
Color Control on your HDTV all the way up to maximum. At least they provide an
option to turn the Bravia Engine Off, which improves things a lot, but not
enough. My suggestion for Sony, retrain your display engineering and marketing
teams in the tradition of the former grand Sony Style…
The Next Generation of Smartphone
Displays:
These are the trends in Smartphone displays that we
expect to see in the upcoming generation of displays.
Sticking with Full HD:
Smartphone cameras are still involved in an absurd Mega
Pixel war, so I hope that both manufacturers and consumers can instead agree on
sticking with Full HD 1920x1080 Smartphone displays for a while. There are lots
of good reasons to do so: there is a tremendous amount of Full HD 1920x1080
content available. Displaying that content at its native resolution (without
the need to rescale up or down) results in the best possible image quality,
plus rescaling requires processing overhead that uses (wastes) precious battery
power.
Smaller Screens:
Screen sizes have been creeping up for years
because of the marketing push to higher display resolutions. If we can stick
with the 1920x1080 resolution then the increases in Pixels Per Inch can instead
be used to begin decreasing screen sizes. Both HTC and LG have already started
on this approach by introducing newer models that are smaller. The HTC One is
4.7 inches with 468 PPI that follows a 5.0 inch 440 PPI model. A 500 PPI Full
HD display will be 4.4 inches, which may appeal to consumers that feel 5.0
inches is too large.
Better Picture Quality in High Ambient Light:
All current displays perform poorly in ambient
light because the reflected light glare progressively degrades the on-screen
colors and image contrast. With improved sensors and color management, displays
will be able to compensate for the effects of ambient light by dynamically changing
the Color Gamuts and Intensity Scales to automatically correct for reflected
glare and image wash out from ambient light. For those interested, I have an
advanced article on this topic in the July/August 2013 issue of the SID Information Display magazine.
DisplayMate Display Optimization Technology
All
Smartphone and Tablets 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,
optimization, 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 in-depth 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.
Display Shoot-Out Comparison Table
Below we
compare the displays on the HTC One, the Huawei Ascend D2, and the Sony Xperia Z based on a wide range of Laboratory
measurement data and objective criteria. For additional background and
information see the Flagship Smartphone
Display Technology Shoot-Out between the OLED Samsung
Galaxy S4 and the LCD Apple iPhone 5.
|
Categories
|
HTC One
|
Huawei
Ascend D2
|
Sony
Xperia Z
|
Comments
|
|
Display Technology
|
4.7 inch
LCD
|
5.0 inch
LCD
|
5.0 inch
LCD
|
Liquid Crystal Display
|
|
Screen Shape
|
16:9 =
1.78
Aspect
Ratio
|
16:9 =
1.78
Aspect
Ratio
|
16:9 =
1.78
Aspect
Ratio
|
All have the same shape as HDTV video
content.
|
|
Screen Area
|
9.4 Square
Inches
|
10.7
Square Inches
|
10.7
Square Inches
|
A better measure of size than the
diagonal length.
|
|
Relative Screen Area
|
88 percent
|
100
percent
|
100
percent
|
Screen Area relative to the Ascend D2
and Xperia Z.
|
|
Display Resolution
|
1920 x
1080 pixels
Full High
Definition
|
1920 x
1080 pixels
Full High
Definition
|
1920 x
1080 pixels
Full High
Definition
|
The more Pixels and Sub-Pixels the
better.
|
|
Pixels Per Inch
|
468 PPI
Excellent
|
443 PPI
Excellent
|
443 PPI
Excellent
|
At a typical viewing distance of 12
inches from the
screen the 20/20 Vision sharpness limit
is 286 PPI.
See this on
the visual acuity for a true Retina Display
|
|
20/20 Vision Distance where Pixels
or Sub-Pixels are not resolved
|
7.3 inches
|
7.8 inches
|
7.8 inches
|
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
|
Full
24-bit color
No
Dithering Visible
256
Intensity Levels
|
Full
24-bit color
No
Dithering Visible
256
Intensity Levels
|
Many Android Smartphones and Tablets
still have some
form of 16-bit color depth
in the Gallery Photo Viewer
|
|
|
HTC One
|
Huawei
Ascend D2
|
Sony
Xperia Z
|
|
|
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
|
Good
Images
Photos and
Videos
have too
much color
and
accurate contrast
See
Figure 1
|
Very Good
Images
Photos and
Videos
have excellent
color
and
accurate contrast
See
Figure 1
|
Good
Images
Photos and
Videos
have too
much color
and
variable contrast
See Figure
1
|
The Viewing Tests examined the accuracy
of
of a large set of challenging
photographic
images by comparing the Smartphone
displays
to a calibrated studio monitor and HDTV.
See Figure
1
|
|
Variation with Viewing Angle
Lab Tests and Measurements
See Details Below
See
Figure 1
|
Small
Color Shifts
with
Viewing Angle
Large
Brightness Shift
with
Viewing Angle
|
Small
Color Shifts
with
Viewing Angle
Large
Brightness Shift
with
Viewing Angle
|
Large
Black Level Rise
with
Viewing Angle
Large
Brightness Shift
with
Viewing Angle
|
All LCDs have a large decrease in
Brightness
with Viewing Angle.
The Sony Xperia Z has a large increase in
the
Black Level with Viewing Angle that
reduces
contrast and washes out the images
|
|
Overall Display Assessment
Lab Tests and Measurements
See Details Below
|
Excellent LCD Panel
|
Excellent LCD Panel
|
Very Good LCD Panel
Poor Viewing Angles
|
The HTC One and Huawei Ascend D2 have
excellent LCD panels.
The Sony Xperia Z has poor Viewing Angles
that wash out the image at small viewing
angles.
|
|
Overall Display Calibration
Lab Tests and Viewing Tests
|
Good Calibration
Too Much Processing
See
Figure 1
|
Excellent Calibration
See
Figure 1
|
Good Calibration
with Bravia Engine Off
See
Figure 1
Poor Calibration
with Bravia Engine On
|
The Huawei Ascend D2 has a much more
accurate display calibration.
The HTC One and Sony Xperia Z have too
much processing and inaccurate colors.
|
|
Overall Display Grade
|
B+
Rank 2
|
A
Rank 1
|
B–
Rank 3
|
The Huawei Ascend D2 has a much better
display
than the HTC One and Sony Xperia Z.
|
|
|
HTC One
|
Huawei
Ascend D2
|
Sony
Xperia Z
|
|
|
Screen Reflections
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. Many
Smartphones still have greater than 10 percent reflections that 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
matte or haze surface finishes.
|
|
Average Screen Reflection
Light From All Directions
|
Reflects
5.6 percent
Very Good
|
Reflects
6.5 percent
Very Good
|
Reflects
5.6 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
|
6.5 percent
Very Good
|
6.9 percent
Very Good
|
6.7 percent
Very Good
|
These are the most annoying types of
reflections.
Measured using a narrow collimated
pencil beam
of light reflected off the screen.
|
|
|
HTC One
|
Huawei
Ascend D2
|
Sony
Xperia Z
|
|
|
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.
|
|
Measured Peak Brightness
100% Full Screen White
|
Brightness
491 cd/m2
Excellent
|
Brightness
421 cd/m2
Excellent
|
Brightness
478 cd/m2
Excellent
|
This is the Brightness for a screen that
is entirely
all white with 100% Average Picture
Level.
|
|
True Black Level
at Maximum Brightness
|
0.40 cd/m2
Very Good
for Mobile
|
0.57 cd/m2
Very Good
for Mobile
|
Black is
0.39 cd/m2
Very Good
for Mobile
|
Black brightness is important for low
ambient light,
which is seldom the case for mobile
devices.
|
|
Dynamic Black Level
at Maximum Brightness
|
0.28 cd/m2
Very Good
for Mobile
|
0.57 cd/m2
Very Good
for Mobile
|
Black is
0.39 cd/m2
Very Good
for Mobile
|
At low Average Picture Levels the
Backlight
on the screen may be automatically
dimmed.
|
|
Contrast Ratio
Relevant for Low Ambient Light
|
1,228 True
1,754
Dynamic
Very Good
for Mobile
|
739 True
739 Dynamic
Very Good
for Mobile
|
1,226 True
1,226 Dynamic
Very Good
for Mobile
|
Only relevant for low ambient light,
which is seldom the case for mobile
devices.
Actual Contrast Ratio is dominated by
Ambient Light.
|
|
Contrast Rating
for High Ambient Light
|
88
Very Good
|
65
Very Good
|
85
Very Good
|
Defined as Maximum Brightness / Average Reflectance.
|
|
Screen Readability in Bright Light
|
Very Good
A–
|
Very Good
A–
|
Very Good
A–
|
Indicates how easy it is to read the
screen
under high ambient lighting. Very
Important!
See High
Ambient Light Screen Shots
|
|
|
HTC One
|
Huawei
Ascend D2
|
Sony
Xperia Z
|
|
|
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.
|
|
White Color Temperature
Degrees Kelvin
|
6,983 K
Very Good
|
User
Adjustable
6,861 K
to 10,540 K
Excellent
|
6,760 K
Very Good
|
D6500 is the standard color of White for
most
Content and needed for accurate color
reproduction.
|
|
Color Gamut
Measured in the dark at 0 lux
See Figure 2
|
Close to
Perfect
101
percent
See Figure 2
|
Close to
Perfect
104
percent
See Figure 2
|
Somewhat
Too Large
115
percent
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 Brightness
Reduction in Luminance with APL
|
4 percent
Very Good
|
None
Excellent
|
None
Excellent
|
This is the percent Brightness reduction
with APL
Average Picture Level. Ideally should be
0 percent.
|
|
Intensity Scale and Image Contrast
See Figure 3
|
Very
Smooth
Contrast
is Excellent
See Figure 3
|
Very
Smooth
Contrast
is Excellent
See Figure 3
|
Contrast
is Irregular 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
|
2.15 to
2.20
Close to
Perfect
|
2.27
Close to
Perfect
|
1.98 to
2.16
Somewhat
Irregular
|
Gamma is the slope of the Intensity
Scale.
Gamma of 2.20 is the standard and needed
for
accurate image reproduction. See Figure 3
|
|
|
HTC One
|
Huawei
Ascend D2
|
Sony
Xperia Z
|
|
|
Viewing Angles
The variation of
Brightness, Contrast, and Color with viewing angle is especially important
for Smartphones 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 Smartphones.
Note that the Viewing
Angle performance is also very important for a single viewer because the
Viewing Angle varies
based on how the
Smartphone is held, and the angle can be very large if the Smartphone is
resting on a table or desk.
|
|
Brightness Decrease
at a 30 degree Viewing Angle
|
61 percent
Decrease
Very Large
Decrease
|
57
percent Decrease
Very Large
Decrease
|
64 percent
Decrease
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
|
606 True
Very Good
for Mobile
|
415 True
Very Good
for Mobile
|
146 True
Very High
Black Level
Poor
|
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’)
= 0.0061
1.5 times
JNCD
|
Small
Color Shift
Δ(u’v’)
= 0.0091
2.3 times
JNCD
|
Small
Color Shift
Δ(u’v’)
= 0.0122
3.1 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’)
= 0.0027
0.7 times
JNCD
|
Small
Color Shift
Δ(u’v’)
= 0.0093
2.3 times
JNCD
|
Large
Color Shift
Δ(u’v’)
= 0.0520
13.0 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.
|
|
|
HTC One
|
Huawei
Ascend D2
|
Sony
Xperia Z
|
|
|
The display power was measured using a Linear
Regression between Luminance and AC Power with a fully charged battery.
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 most challenging
issue when increasing display resolution and PPI is the decrease in light
output and display power
efficiency due to the
proportional increase of the Active Matrix Thin Film Transistors (AM TFTs)
that drive the display.
Since the thickness and
weight of a Smartphone are crucial, the displays cannot use amorphous Silicon
(aSi), which is
used in most Smartphones
and Tablets, because it is very inefficient at high PPI, and instead need to
use much higher
performance (and higher
cost) Low Temperature Poly Silicon (LTPS) or (for Sharp displays) Continuous
Grain Silicon (CGS).
All of the displays have
very similar and very good Power Efficiency. For reference, the iPhone 5 with
a much lower 326 PPI
has a Relative Display
Power Efficiency of 0.90 watts, which is about 20 percent more power
efficient than the 440+ PPI displays.
|
|
Maximum Display Power
Full White Screen
at Maximum Brightness
|
1.05 watts
|
1.12 watts
|
1.21 watts
|
This measures the display power for a
screen
that is entirely White at Maximum
Brightness.
|
|
Relative Display Power Efficiency
same Luminance 421 cd/m2
same 5.0 inch screen area
|
1.03 watts
|
1.12 watts
|
1.07watts
|
This compares the Average Power
Efficiency
by using the same screen brightness and
the
same screen area for all the displays.
The iPhone 5, with a smaller 326 PPI
display,
has a Relative Power Efficiency of 0.90
watts.
|
|
|
HTC One
|
Huawei
Ascend D2
|
Sony
Xperia Z
|
|
|
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.
|
|
Running Time
at Maximum Display Power
|
Not Yet Available
Coming Soon
|
Not Yet Available
Coming Soon
|
Not Yet Available
Coming
Soon
|
Display always On at Maximum power with
Airplane Mode and no running
applications.
|
|
Categories
|
HTC One
|
Huawei
Ascend D2
|
Sony
Xperia Z
|
Comments
|
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.
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