new iPad Display Technology Shoot-Out
iPad 2 – new iPad – iPhone
4
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
Introduction
The iPad has been a
phenomenal runaway success – to a degree that may have even surprised Steve Jobs.
At the new iPad launch Tim Cook remarked that people have been wondering who
would improve upon the iPad. Amazingly, but to no one’s surprise, that would be
Apple (again). Much to my delight the new Retina Display is its flagship and
number one marketing feature. Tablets, after all, are essentially large
portable displays so a top notch display is the key to a successful product –
something most manufacturers haven’t figured out yet. Apple has from day 1 –
and the new iPad Retina Display is impressive – Apple calls it “Resolutionary.”
This article will be a combination of objective praise and critical analysis of
the Retina Display on the new iPad.
First of all, the Apple
Retina Display is pure marketing brilliance. While the enhanced screen
resolution is getting most of the attention, the enhanced color saturation is
equally responsible for its wow factor. These are the two wonders of the new
iPad. Both are technically challenging because they require lots of additional
battery power. In fact, the battery on the new iPad has 70 percent higher
capacity than the iPad 2.
While the enhanced
resolution is important, it’s also a technical overkill that parallels the Mega
Pixel wars of digital cameras. More pixels are better up to a point, and then
they wind up adversely affecting both performance and manufacturing costs. To a
certain extent that is definitely the case for the new iPad as we explain
below. Still Apple has managed to pull everything together nicely so that in
the end it all performs quite well. Just as surprising is that Apple has
managed to keep the retail price the same as the iPad 2. That’s the third
wonder of the new iPad. We will show and tell you below a lot more than you’ll
learn anywhere else about the iPad Retina Display…
A true “Retina Display” but not an actual Retina Display
The
original Retina Display on the iPhone 4 has 326 pixels per inch (ppi). But to
qualify as an Apple Retina Display the new iPad does not require the same ppi
as the iPhone 4 Retina Display because it is typically held further away from
the eye, whose visual sharpness is based on angular resolution rather than the
linear ppi resolution on the display. The iPad is typically held 15-18 inches
away as opposed to the iPhone 4’s 12-15 inches. As a result, to meet the 300
ppi Retina Display specification made by Steve Jobs at WWDC for the iPhone 4,
an iPad Retina Display only needs 240 ppi – and it has 264 ppi. So according to
Apple’s own definition, the new iPad is indeed a true “Retina Display.”
However, Apple’s definition of a “Retina Display” is
actually for 20/20 Vision (defined as 1 arc-minute visual acuity). 20/20 Vision
is just the legal definition of “Normal Vision,” which is at the lower end of
true normal vision. There are in fact lots of people with much better than
20/20 Vision, and for almost everyone visual acuity is actually limited by
blurring due to imperfections of the lens in the eye. The best human vision is
about 20/10 Vision, twice as good as 20/20 Vision, and that is what corresponds
to the true acuity of the Retina. So to be an actual “True Retina Display” a
screen needs at least 573 ppi at 12 inches viewing distance or 458 ppi at 15
inches. The 326 ppi iPhone 4 is a 20/20 Vision display if it is viewed from
10.5 inches or more. Unfortunately, a “20/20 Vision Display” doesn’t sound
anywhere near as enticing as a “Retina Display” so marketing and science don’t
see eye-to-eye on this…
Do you really need all
of that resolution and sharpness?
I
am definitely not proposing a new display Mega Pixel war for 400+ ppi (but several
manufacturers are working on it, so we’ll see). The new iPad display is
incredibly sharp with 264 ppi and 3.1 million pixels on a 9.7 inch screen. The
iPad 2 screen with 132 ppi, a resolution of 1024x768 and 0.8 million pixels is noticeably
pixelated, but was it really necessary to double the resolution and therefore
quadruple the number of pixels? Marketing considerations aside, the real reason
for doubling the iPad’s resolution to 2048x1536 is for the convenience and ease
in up-scaling the older 1024x768 Apps from the iPad 1 and iPad 2 – every older
App pixel is simply replicated 2x2=4 times. Rescaling to lower resolutions like
1600x1200 would have required more complicated processing, but the high power
A5X processor on the new iPad could have easily handled that.
Marketing
considerations aside, do you really need all of that “Retina Display”
resolution and sharpness? In many cases no, for these five reasons: 1. Most adults don’t
actually have true corrected 20/20 Vision even with glasses or contact lenses.
2. If you view the display
further away than the recommended viewing distance your eye can no longer fully
resolve the sharpness of the display, so that high resolution is wasted. 3. Unlike computer
graphics images, photographic images (including videos) are inherently fuzzy,
with the sharpest image detail spread over multiple pixels. Similarly, you
would be hard pressed to visually tell the difference between 640x480 and
2048x1536 photographic images of a (Granny Smith) Apple. 4. Sub-pixel rendering,
rather than ordinary pixel rendering, will significantly improve the visual
sharpness of any display, especially for computer generated text and graphics,
so that is the most efficient approach to improving sharpness. 5. Most people don’t even
have 1600x1200 resolution on the much larger 15-19 inch screens on their (Apple
or Windows) laptops and desktop monitors and are happy with them (even the tech
journalists that I asked).
So
where will the 2048x1536 3.1 Mega Pixel Retina Display actually make a
noticeable visual improvement over other displays? All (computer generated)
text will appear much sharper, but it will make the most difference whenever
there is tiny text and fine graphics, which you often see when surfing the web (like
the front page of The New York Times) or in a complex spreadsheet. Then there
is a tremendous visual difference between the new iPad and the iPad 2 or
existing Android Tablets. You won’t have to zoom in as much or switch to
Landscape mode as often when reading tiny web content. Full screen high quality
photographs with lots of fine detail will also stand out and take full
advantage of the new iPad’s High Definition screen. The larger Tablet format
also makes the iPad appear visually sharper and more stunning than the much
smaller (and higher ppi) iPhone 4. One final note on Retina Displays: your
existing HDTV is already a Retina Display. For example, a 1080p 46 inch TV
viewed from 6 feet or more and a 1080p 60 inch TV viewed from 8 feet or more
(the typical TV viewing distance in the US is 9 feet) are already 20/20 Vision
"Retina Displays" so don’t worry about upgrading them to get Retina
Display resolution and sharpness…
IGZO and other Apple display Rumors explained
A high resolution
display for the iPad 2 and then the “iPad 3” was the number one rumor in the
tech world for all of 2011. In fact, it resulted in hundreds (possibly
thousands) of rumors for if, when, where, and how it would be done. Actually,
the question was not whether it could be done, but rather whether it could be
done with satisfactory yields, production volumes, and costs. While Apple was
rumored to have invested in production facilities for Sharp, essentially all of
the advanced display technology for Apple displays comes from its three
principal display suppliers: LG, Samsung and Sharp. Chimei Innolux and Au
Optronics also supply displays. In many cases new Apple products launch with
just a single supplier (rumored this time to be Samsung for the new iPad) and
then expand to between 3 and 5 suppliers for high volume products like the iPad
and iPhone. New teardown reports now indicate that there are actually 3
suppliers at launch: Samsung, LG, and possibly Sharp.
The iPad 2 uses
amorphous Silicon for the LCD Active Matrix Thin Film Transistors (AM TFTs),
the same display technology found in most Tablets, laptops, and desktop
monitors. On the other hand, the iPhone 4 uses Low Temperature Poly Silicon
(LTPS) because the much higher ppi requires smaller AM TFTs in order to
maintain satisfactory brightness and efficiency. However, it’s more complex and
costly to produce. One of the biggest rumors was that Apple was going to use
Sharp’s IGZO (Indium Gallium Zinc Oxide), which is better at high ppi and lower
cost than LTPS. But it’s a new technology and Sharp publicly announced in
December that it was experiencing startup delays. LG and Samsung have also been
working on IGZO technology. The question is when, not if, this technology will
be coming to future Retina Displays (and non-Apple Tablets and Smartphones). It
will also be coming to laptops, monitors, and televisions, possibly even
Apple’s. Our lab measurements show that IGZO is desperately needed for the new
iPad high ppi display because of the high power and large batteries it
currently needs. And, counter to the rumor mill, IGZO can do IPS (in Plane
Switching) technology that is found on the iPad 2 and iPhone 4 displays, see
below.
So what display
technology is in the new iPad? According to DisplaySearch it is still amorphous
Silicon that has been pushed to its extreme upper ppi limit. Apple
has a nice video on their website that discusses advanced dual plane LCD
technology that they say is there to reduce sub-pixel crosstalk in the new
iPad. It’s actually technology originally developed by Sharp and other
companies to increase the aperture ratio and brightness efficiency of these
very high ppi LCDs. Another interesting display technology mystery: while
Apple’s official website Tech Specs and Features list IPS (In Plane Switching)
as the LCD technology used in both the iPads and iPhone 4/4S (which provides
wide viewing angles) the displays from all suppliers actually come with FFS
(Fringe Field Switching) licensed from Hydis, which is related to IPS
technology. This is also the case for many Android Tablets, including the
Amazon Kindle Fire, Barnes & Noble Nook Tablet, and even the Samsung Galaxy
Tab 10.1.
The Shoot-Out
To compare the performance of the new iPad we ran our
in-depth series of Display
Technology Shoot-Out tests on the new iPad. We take display quality very
seriously and provide in-depth objective analysis side-by-side comparisons with
the iPad 2 and iPhone 4 based on detailed laboratory measurements and extensive
viewing tests with both test patterns and test images. We used the iPhone 4
rather than 4S because it performs slightly better. For comparisons with other
“popular” Tablets see our 10 Inch Tablet Display
Technology Shoot-Out and our IPS Tablet Display
Technology Shoot-Out for comparisons with the Amazon
Kindle Fire and Barnes & Noble Nook Tablet.
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 Reflections, Brightness and Contrast, Colors and Intensities, Viewing Angles, Display Backlight Power Consumption,
Running Time on Battery, and Battery Charging Issues.
Comparison with the iPad 2 and current Android
Tablets: The display on the new iPad decisively beats (blows away) all of
the Tablets we have previously tested including the iPad 2 (below), the Samsung Galaxy Tab 10.1,
the Barnes &
Noble Nook Tablet, and the Amazon Kindle Fire
at the back of the pack. The articles also show that the iPad 2 display has
recently slipped behind the Galaxy Tab and Nook Tablet. See the Conclusion section below for the evaluation and the
article links for other tested Tablets.
Display Sharpness: As expected, all of
the images, especially the text and graphics, were incredibly and impressively
razor sharp. In some photographs, that extra sharpness made a significant
difference, especially in close-ups and when fine detail like text was
photographed.
Improved Color Saturation and Color Accuracy: A major shortcoming of
the iPad 2 and iPhone 4 is their reduced Color Gamut, they only have
61-64 percent of the sRGB-Rec.709 Standard Color Gamut needed for accurate
color reproduction. That produces images with noticeably under saturated
colors, particularly reds, blues and purples. This is due to efficiency issues
from the Backlight LEDs. Apple claims “44 percent greater color saturation.”
Technically it’s not clear what that means in this context, but the new iPad
has a virtually perfect 99 percent of the Standard Color Gamut (a 38 percent
improvement over the iPad 2). The colors are beautiful and accurate due to very
good factory calibration – they are also “more vibrant” but not excessively so
or gaudy like some existing OLED displays. See the Conclusion
below for our overall assessment and the screen shots for a
side-by-side screen comparison.
Viewing Tests: What makes the new iPad really shine is its very accurate
colors and picture quality. It’s most likely better and more accurate than any
display you own (unless it’s a calibrated professional display). In fact with
some minor calibration tweaks the new iPad would qualify as a studio reference
monitor. See our detailed Color and Intensity
Scale measurements below.
The new iPad as a Camera: The main (rear) camera on the iPad 2 was awful
but the camera on the new iPad appears to be the same as the camera on the
iPhone 4, and it does take very good photos, but no where near as nice as a
DSLR camera. Many reviewers have commented that it’s awkward and dorky to hold
up a Tablet to take a photo. But the real advantage of the new iPad over any
other camera is that you immediately see your photo on a beautiful and color
accurate 9.7 inch display. Even $2,000 DSLRs have only 3 inch low resolution
screens, which are less than one tenth the area of the iPad screen, so you
really don’t know how good your photo is until you download it later on after
the opportunity to take a better shot is gone (the same problem that film
cameras had). Fortunately, DSLR cameras are beginning to offer WiFi.
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 sharpness and colors can
noticeably degrade from light reflected by the screen, especially objects like
your face and any bright lighting behind you. Screen Reflectance on the new
iPad is 7.7 percent, in the middle of the range that we have seen for Tablets
and Smartphones. The best we have ever measured in our lab tests are the Samsung Galaxy S
and the Nokia Lumia 900 with its ClearBlack display, with about half of the
Reflectance of the new iPad, and the current worst is the Amazon Kindle Fire,
with about double the Reflectance of the new iPad. This article
shows how screen images degrade in bright ambient light.
Viewing Angle Performance: According to Apple the new iPad has an IPS LCD
like the iPad 2 and iPhone 4, and our lab measurements confirmed excellent
Viewing Angle performance, with no noticeable color shifts. However, all LCDs,
including IPS LCDs, do have a strong decrease in brightness with Viewing Angle,
and the new iPad performed as expected, with a 57 percent decrease in
brightness at just 30 degrees Viewing Angle. The Viewing Angle performance for
the new iPad, iPad 2 and iPhone 4 are all virtually identical.
Much Lower Display Power Efficiency: The new iPad uses 2.5 times the
Backlight power of the iPad 2 for the same screen Brightness. As discussed above that results from the TFT transistors in the LCD
blocking much more of the light at higher ppi. On the other hand, the highest ppi
iPhone 4 is the most power efficient display of all because it uses Low
Temperature Poly Silicon LTPS, which is much more efficient than amorphous Silicon
in the iPads. All of this points to the need for the IGZO display technology
discussed above, which is lower cost than LTPS, and more
efficient so it can use smaller batteries. IGZO should be in production
shortly, and is the first in a whole series of enhanced Metal Oxide semiconductors for LCD and
OLED displays.
Much more Power and Battery but not Thickness or
Weight: There
are 4 times as many pixels in the display that need to be kept powered. Also 4
times as much memory and processing power is needed for the images. In
addition, the light transmission of the LCD decreases as the pixel density
increases, so a brighter Backlight is necessary. In fact, the number of
Backlight LEDs has roughly doubled (from 36 to an estimated 72 to 82), so the
Backlight power has approximately doubled. Since the display normally consumes
about 50-60 percent of the total Tablet power, the new iPad needs at least a 50
percent larger battery. In fact, the battery increased from 25 to 42.5 watt
hours, a 70 percent increase. Our measured Backlight power for the new iPad is
2.5 times the iPad 2 for the same screen brightness. In spite of the larger
battery the running time at Maximum brightness in our tests was 5.8
hours, 20 percent less than the iPad 2’s 7.2 hours. But at the Middle
brightness slider setting, which is closer to typical user settings, the
running time was 11.6 hours, which is almost identical to the iPad 2,
indicating that Apple has used an appropriately larger battery (and confirms
Apple’s 10 hour claim). Surprisingly the overall iPad thickness increased by
only 0.6mm (0.03 inches) and the weight increased by only 1.8 ounces (8
percent). That small increase in weight in spite of 70 percent more battery
capacity indicates that the case and cover glass are significantly lighter.
new iPad Conclusion: Impressive… but Lots
of Room for Improvement
Apple
has taken the very good display on the iPad 2 and dramatically improved two of
its major weak points: sharpness and color saturation – they are now
state-of-the-art. Our lab tests and visual tests agree with Apple’s claim that
the new iPad has “the
best display ever on a mobile device” so we have awarded the new iPad the Best Mobile Display Award
in DisplayMate’s Best Video
Hardware Guide. But there’s more… the new iPad’s
picture quality, color accuracy, and gray scale are not only much better than
any other Tablet or Smartphone, it’s also much better than most HDTVs, laptops,
and monitors. In fact with some minor calibration tweaks the new iPad would
qualify as a studio reference monitor. So we have also awarded the new
iPad the Best Mobile
Picture Quality Award, which was previously held by the original Motorola
Droid (not the more recent Droids, which all have poor picture quality).
Finally, almost as impressive is that Apple has
maintained the base price of $499. Who says Apple doesn’t compete aggressively
on price!
Many New Professional Level Applications:
With
this degree of picture quality and accuracy the iPad is now qualified for many
interesting professional level applications. If you are a professional (or
serious amateur) photographer the new iPad will show your photographs more
accurately than any other display you have (unless it’s a calibrated
professional display). More importantly, for medical imaging – every MD should
have one for both mobile and office use. It will also be great for anyone that
needs to refer to detailed documents and manuals – like field service
technicians (millions of them), warehouse workers, and pilots just to name a
few. Tens of millions of sales people often need a portable device that
displays very sharp and accurate color representations of their products and
sales information. For this the new iPad beats every laptop, Tablet, and mobile
projector I have seen. It’s impressive, but there is still…
Lots of Room for
Improvement by Apple and Other Manufacturers:
If
you read our earlier Mobile
Display Shoot-Outs for the iPhone 3GS, iPhone 4, and iPad 2, it certainly
appears that Apple has been following our display advice (see Figure 3 on the evolution of
the iPhone and iPad gray scale). So what’s next… While Apple has zeroed in on
sharpness and done an excellent job of it, and improved the color saturation
and color accuracy to an impressive level, there are still plenty of other very
important display issues that need to be addressed by all of the Tablet and
Smartphone manufacturers, including Apple. Here are just a few: 1. Screen Reflectance: The typically large screen
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. Manufacturers need to significantly reduce the mirror
reflections with anti-reflection coatings and haze surface finishes. This article
shows how Tablet and Smartphone screens degrade as the Ambient Light increases
from 0 to 40,000 lux. 2. Ambient Light Sensor: The forward facing Ambient Light Sensor on virtually all
Tablets and Smartphones measures the brightness of your face instead of the
surrounding ambient light, which is what is needed to accurately set the
screen’s Automatic Brightness. 3. Automatic
Brightness: The Automatic Brightness controls on all Tablets and Smartphones that we
have measured are positively awful and close to functionally useless. As a
result they often get turned off, which reduces battery run time and increases
eye strain. This article
explains how to do it properly. 4. Display
User Interface: The User Interface for
most Tablet and Smartphone displays consists of a Brightness slider and an
Automatic Brightness checkbox. People have very different visual preferences
that should be accommodated with a display Pizzazz control that is similar to
the functionality provided by the audio Equalizers found on most Tablets and
Smartphones. 5. RGB LED Backlights: Using separate red, green and blue Backlight LEDs instead
of just white LEDs will allow more accurate calibration, allow the image color
saturation to be increased under high ambient lighting, and also accommodate
people that like extra vibrant rather than accurate colors on-screen. 6. OLED Displays: Once
their cost significantly decreases and their power efficiency and production
volumes significantly increase we’ll start to see lots of Tablets with OLED
displays. Until then, IPS LCDs can’t be beat. 7. Size: Tablets are so useful that there is
plenty of room for 7 inch, 10 inch, and even 12+ inch screens – the first for
extra portability and the latter for professional and office applications… and
there are lots of people that would own more than one size based on their
varying needs. One of the more credible rumors flying around is that Apple will
introduce a 7-8 inch 1024x768 iPad in 2012. I hope so… and so does my daughter,
saying it will then fit in her handbag.
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 can
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.
Display Shoot-Out Comparison Table
Below we
compare the displays on the iPad 2, new iPad, and iPhone 4 based
on objective measurement data and criteria. For additional background, context,
and information see the Tablet Display
Technology Shoot-Out article that compares the larger Motorola Xoom, Asus Transformer, Acer Iconia A500, and Samsung
Galaxy Tab 10.1 Tablets with the Apple iPad 2, and the IPS Tablet Display
Technology Shoot-Out that compares the Amazon
Kindle Fire, Barnes & Noble Nook Tablet
with the iPad 2.
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Categories
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Apple
iPad 2
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Apple
new iPad
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Apple
iPhone 4
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Comments
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Display Technology
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9.7 inch
IPS LCD
Amorphous
Silicon
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9.7 inch
IPS LCD
Amorphous
Silicon
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3.5 inch
IPS LCD
Low Temperature
Poly
Silicon
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Liquid Crystal Display
In Plane Switching
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Screen Shape
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4:3 =
1.33
Aspect
Ratio
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4:3 =
1.33
Aspect
Ratio
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3:2 = 1.50
Aspect
Ratio
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The iPad screen has the same shape as
8.5x11 paper.
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Display Resolution
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1024 x 768
pixels
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2048 x
1536 pixels
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960 x 640
pixels
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The more Pixels and Sub-Pixels the
better.
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Typical Viewing Distance
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15 to 18
inches
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15 to 18
inches
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12 to 15
inches
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Typical Ranges for Normal Viewing
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Pixels Per Inch
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132 ppi
Noticeably
Less Sharp
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264 ppi
Excellent
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326 ppi
Excellent
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At 12 inches from the screen 20/20 vision
is 286 ppi.
Best human vision is about 20/10 vision
or 573 ppi.
See this on
the visual acuity for a true Retina Display
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Retina Display at Viewing Distance
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No
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Yes
Exceeds
240 PPI
at Viewing
Distance
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Yes
Exceeds
300 PPI
at Viewing
Distance
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300 PPI for the iPhone 4 is Apple’s own
definition
of a Retina Display at its Viewing
Distance..
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On-Screen Displayed Color Depth
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Full
24-bit color
256 Intensity
Levels
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Full
24-bit color
256
Intensity Levels
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Full
24-bit color
256
Intensity Levels
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24-bit displays produce images with
relatively
smooth and artifact free colors and
intensities.
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Gallery / Photo Viewer Color Depth
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Full
24-bit color
256
Intensity Levels
Very Good
Calibration
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Full
24-bit color
256
Intensity Levels
Very Good
Calibration
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Full
24-bit color
256
Intensity Levels
Very Good
Calibration
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Most Android Tablets and Smartphones
still have
only 16-bit color
depth in the Gallery Photo Viewer.
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iPad 2
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new iPad
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iPhone 4
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Overall Assessments
This section summarizes
the results of all of the extensive Lab measurements and viewing tests
performed on all of the displays.
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Viewing Tests
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Good
Images
Photos and
Videos
have too
little color
and too
much contrast
Small
Color Shifts
with
Viewing Angle
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Very Good
Images
Photos and
Videos
have
accurate color
and
accurate contrast
Small
Color Shifts
with
Viewing Angle
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Good
Images
Photos and
Videos
have too
little color
and too
much contrast
Small
Color Shifts
with
Viewing Angle
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The Viewing Tests examined the accuracy
of
photographic images by comparing the
displays
to a calibrated studio monitor and HDTV.
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Overall Display Assessment
Lab Tests and Viewing Tests
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Very Good Display
For Second Generation
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Excellent Display
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Excellent Display
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The iPad 2 was a Very Good Display for
its time.
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Current Overall Display Grade
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B
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A
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A–
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The new iPad is decisively better than
the competition
but not close to A+ as discussed in the Conclusion.
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iPad 2
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new iPad
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iPhone 4
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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.
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Average Screen Reflection
Light From All Directions
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8.7 percent
Good
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Reflects
7.7 percent
Very Good
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Reflects
7.0 percent
Very Good
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Measured using an Integrating
Hemisphere.
The best value we have measured is 4.4
percent
and the current worst is 14.8 percent.
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Mirror Reflections
Percentage of Light Reflected
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10.8 percent
Poor
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9.9 percent
Good
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8.1 percent
Good
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These are the most annoying types of
reflections.
Measured using a narrow collimated
pencil beam of
light reflected off the screen.
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iPad 2
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new iPad
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iPhone 4
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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.
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Measured Maximum Brightness
is the Peak Luminance for White
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Brightness
410 cd/m2
Very Good
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Brightness
421 cd/m2
Very Good
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Brightness
541 cd/m2
Excellent
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Maximum Brightness is very important for
mobile
because of the typically high ambient
light levels.
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Black Level
at Maximum Brightness
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Black is
0.43 cd/m2
Very Good
for Mobile
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Black is
0.48 cd/m2
Very Good
for Mobile
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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.
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Contrast Ratio
Relevant for Low Ambient Light
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962
Very Good
for Mobile
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877
Very Good
for Mobile
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1,117
Very Good
for Mobile
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Only relevant for low ambient light,
which is seldom the case for mobile
devices.
Defined as Maximum Brightness / Black
Brightness.
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Contrast Rating
for High Ambient Light
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47
Good
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55
Good
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77
Very Good
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Defined as Maximum Brightness / Average Reflectance.
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Screen Readability in Bright Light
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Good B
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Good B+
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Very Good A
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Indicates how easy it is to read the
screen
under high ambient lighting. Very
Important!
See High
Ambient Light Screen Shots
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|
|
iPad 2
|
new iPad
|
iPhone 4
|
|
|
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
|
6,991
degrees Kelvin
Slightly
Too Blue
|
7,085
degrees Kelvin
Slightly
Too Blue
|
7,781
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
|
Color
Gamut Too Small
61 percent
of Std
See Figure 2
|
Excellent
99 percent
of Std
See Figure 2
|
Gamut Too
Small
64 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 Contrast or Backlight
|
No
Excellent
|
No
Excellent
|
No
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 But
Contrast
Too High
|
Very
Smooth
Contrast
is Perfect
|
Very
Smooth But
Contrast
Too High
|
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 2.66
Gamma Too
High
|
Outstanding
2.20
Gamma is
Perfect
|
Good 2.68
Gamma Too
High
|
Gamma is the slope of the Intensity
Scale.
Gamma of 2.2 is the standard and needed
for
accurate image reproduction. See Figure 3
|
|
|
iPad 2
|
new iPad
|
iPhone 4
|
|
|
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
|
|
Brightness Decrease
at a 30 degree Viewing Angle
|
58 percent
Decrease
Falls to
171 cd/m2
Very Large
Decrease
|
57 percent
Decrease
Falls to
182 cd/m2
Very Large
Decrease
|
57 percent
decrease
to 235
cd/m2
Very Large
Decrease
|
Screens become less bright when tilted.
LCD brightness variation is generally
very large.
|
|
Contrast Ratio
at a 30 degree Viewing Angle
|
564
Very Good
for Mobile
|
526
Very Good
for Mobile
|
556
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’)
= 0.0100
2.5 times
JNCD
|
Small
Color Shift
Δ(u’v’)
= 0.0046
1.2 times
JNCD
|
Small
Color Shift
Δ(u’v’)
= 0.0096
2.4 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’)
= 0.0047
1.2 times
JNCD
|
Small
Color Shift
Δ(u’v’)
= 0.0073
1.8 times
JNCD
|
Small
Color Shift
Δ(u’v’)
= 0.0097
2.4 times
JNCD
|
JNCD is a Just Noticeable Color Difference.
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.
Color Shifts for non-IPS displays are
about 10 JNCD.
|
|
|
iPad 2
|
new iPad
|
iPhone 4
|
|
|
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 new iPad uses 2.5 times the Backlight power of
the iPad 2 for the same screen brightness.
The highest ppi iPhone 4 is the most efficient of
all because it uses Low Temperature Poly Silicon LTPS (see above).
|
|
Display Backlight Power
at Maximum Brightness
|
2.7 watts
|
7.0 watts
|
0.42 watts
|
Lower power consumption is important for
energy
efficiency and improving running time on
battery.
|
|
Display Backlight Power Efficiency
same Peak Luminance 421 cd/m2
same 9.7 inch screen size area
|
2.8 watts
|
7.0 watts
|
2.6 watts
|
This compares the Relative Power
Efficiency
by looking at the same screen brightness
and
screen area.
|
|
|
iPad 2
|
new iPad
|
iPhone 4
|
|
|
Running Time on Battery
The running time on battery was determined with the
Brightness sliders at the Maximum and Middle (center) settings,
in Airplane Mode, with no running applications, and
with Auto Brightness turned off. Note that the batteries do not
actually reach full charge when 100% is shown and
need up to an extra hour before the charging actually stops.
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 the Maximum Brightness Setting
|
7.2 hours
|
5.8 hours
|
7.8 hours
|
Display always On at the Maximum setting
with
Airplane Mode and no running
applications.
|
|
Running Time
At the Middle Brightness Setting
|
11.8 hours
|
11.6 hours
|
12.2 hours
|
Display always On at the Middle slider
setting with
Airplane Mode and no running
applications.
|
|
Categories
|
iPad 2
|
new iPad
|
iPhone 4
|
Comments
|
Battery Charging and Running Time Issues
The outstanding very high performance Retina
Display on the new iPad requires a lot more power than the iPad 2 because it is
pushing the upper limits of amorphous Silicon LCD technology. In fact, it has a
rather large 42.5 watt hour battery that is 70 percent larger than the battery
on the iPad 2. Because of both power and heat limitations the monstrous battery
takes a lot longer to charge, and if you don’t fully charge it you will get
shorter running times. Below we explain these issues, measure the actual
battery charging and running time performance, and also discuss Apple’s
shocking comment that the extended charging time could “harm the longevity of
the battery.”
Recharging the new iPad battery
It takes a relatively long time to recharge the
massive battery in the new iPad – over 5˝ hours when it is fully discharged.
That’s only if the new iPad is off or in sleep mode – if you try recharging
while using the new iPad I estimate that it will take about 20 hours if the
display is set to Maximum Brightness. But when is the battery fully charged?
While preparing to measure the battery running
time to evaluate the Retina Display’s load on the iPad battery I noticed that
the power meter indicated that the iPad AC charger was still continuing to
deliver close to the full 10 watt recharging power long after the screen
indicator showed that the battery was 100% charged – the additional time is slightly
over 1 hour if the new iPad is off or in sleep mode, and slightly over 2 hours
if it is on. Since I wanted to measure the proper maximum running time for a
fully charged battery I waited until the recharging power dropped, indicating
that the battery was actually full and the charging cycle was completed.
But if you stop charging the iPad when the
battery indicator says 100% you won’t get the maximum running time – something
that is very important to many people. Let’s see how much less…
new iPad running time based on a fully
charged battery is 11.6 hours
Starting with a truly fully charged battery as
described above, the battery running time for the new iPad at the Middle
Brightness Slider setting is 11.6 hours. That is in Airplane Mode with no WiFi,
with no activity or running Apps of any sort, and with Auto Brightness Off –
the same running conditions specified on the Apple website. Note that you’ll
get only about half that running time at the Maximum Brightness Slider setting,
but it delivers 2.8 times the Brightness (Luminance) of the Middle Brightness
Slider setting – see the Running Time on
Battery measurement results above.
new iPad running time based on the 100%
battery indicator is 10.4 hours
If you stop charging the iPad when the battery
indicator says 100% you won’t get the maximum running time – something that is
very important to many people. I repeated the Battery Running Time measurements
exactly as above, but stopped the battery charging when the battery indicator
reached 100%. For the new iPad at the Middle Brightness Slider setting the
Running Time decreased by 1.2 hours to 10.4 hours (10 percent). While at first
sight this appears consistent with Apple’s own “up to 10 hours running time” my
tests were in Airplane Mode with no WiFi and no activity or running Apps of any
sort – just a static display. The 11.6 hour running time above for a fully
charged battery would most likely deliver a real use running time of over 10
hours as indicated by Apple, but the 10.4 hour time would most likely not.
What’s the matter with
the battery indicator?
The battery charge indicator on all mobile
devices is based on a mathematical model of the charge rates, discharge rates,
and recent discharge history of the battery. It uses this information to
estimate how much running time is left. It's actually rather difficult to do
because most batteries degrade slowly as they discharge and then tend to
surprise with a precipitous decline near the end. Note that batteries are based
on complex chemistry so there is no practical way to measure the charge level
“in hardware.” So there is something wrong with the battery charge mathematical
model on the iPad. It should not say 100% until it actually stops recharging
and goes from the full recharging rate of about 10 watts to a trickle charging
rate of about 1 watt. Otherwise the user will not get the maximum running time
that the iPad is capable of delivering.
Conclusion – the battery is only 90% charged when it says 100%
So, when the battery indicator first says 100%
the battery is actually only 90% charged and you get 1.2 hours less running
time. It takes an additional 1 to 2 hours to fully charge the battery as
explained above. However, anyone that recharges their iPad unattended (and off
or in sleep mode), especially overnight, will get the necessary extra charging
time and get the full running time indicated above.
Apple has subsequently released a statement
saying that this is by design and as they intended. Maybe so, but why? ALL of our results are
technically correct EXACTLY as stated above. So what’s the REAL reason – it
isn’t the one mentioned in Apple’s statement. The battery charging rate gets
slower and slower as it approaches full charge, so Apple decided to show 100%
sooner so that people didn’t notice or get annoyed by the long and slow final
creep up to the true 100% charge level. The last hour in the long 6˝ charging
cycle is painfully slow, so that becomes invisible if the battery indicator is
accelerated up to 100% for that final hour. It’s all done to improve the
quality of the user experience...
Could the new iPad be damaging its own
battery?
Apple’s most recent statement
also corrects their earlier unfortunate and incorrect remark that keeping the
battery charging after the battery indicator reaches 100% could damage the
battery. I am keeping this section intact for the record because of the
incredible firestorm that ensued.
While my interpretation is that this is just
simply an issue of correcting the on-screen battery indicator so that it
matches and agrees with what the battery charging hardware and software
actually do, Apple PR originally put forth a rather shocking reverse
perspective that the on-screen battery indicator is instead the correct one. As reported by Jon Fortt
of CNBC: "Apple
is saying... if you charge it more than [when the battery indicator reads
100%], you could actually harm the longevity of the battery." This statement
was made by an official Apple PR representative directly to Jon Fortt. How do I know this?
Because Jon Fortt called me immediately after he spoke to Apple PR and we
discussed Apple’s statement together. As I indicate below, it is my feeling that this
was a misguided off-the-cuff remark by an Apple representative to make
everything sound just fine, but they really didn’t know or understand the
repercussions of what they were saying. But if we take their statement at face
value, it unfortunately implies that the new iPad is damaging its own battery.
I logically explore the repercussions of this remark next.
If the Apple PR remark made to Jon Fortt of CNBC was
in fact correct – then damaging the longevity of the battery is exactly what the
new iPad’s internal battery charging hardware and software are doing since it
is their responsibility to properly control and manage the battery recharging
process. It’s pretty obvious that if the new iPad knows that it is fully
charged then it should automatically stop the charging! So according to Apple PR
the new iPad is then configured to damage the longevity of its own battery if
it isn’t manually disconnected from the AC charger when the 100% indicator
appears. Anyone that recharges their iPad unattended, especially overnight,
would then be doing this.
While Apple’s remark might apply to recharging
dumb battery operated toys, the new iPad is a very sophisticated and expensive
computer device that is fully capable of properly controlling and managing its
own (rudimentary) battery charging process. Perhaps Apple should instead retract the remark
and graciously accept my interpretation and rescind their own remarks, which
sound like very poorly thought out PR damage control. On the other hand, if
the Apple PR remark is correct, then Apple needs to immediately fix the iPad
battery charging algorithm or they may be held responsible for replacing all
iPad batteries. Which one will it be?
Apple’s most recent statement
corrects their earlier unfortunate and incorrect remark. It’s perfectly fine to
leave the battery charging all day or all night. As Gilda Radner of Saturday
Night Live used to say… Never Mind!
A Reminder – the new iPad Retina Display is Impressive
While the battery charging issue has taken on a
life of its own, the true subject of this article is the new iPad’s outstanding
Retina Display. To read about that start at the Introduction, the Highlights,
or the Conclusion.
About the Author
Dr. Raymond Soneira is
President of DisplayMate Technologies Corporation of Amherst, New Hampshire,
which produces video calibration, evaluation, and diagnostic products for
consumers, technicians, and manufacturers. See www.displaymate.com. He is a research
scientist with a career that spans physics, computer science, and television
system design. Dr. Soneira obtained his Ph.D. in Theoretical Physics from
Princeton University, spent 5 years as a Long-Term Member of the world famous
Institute for Advanced Study in Princeton, another 5 years as a Principal
Investigator in the Computer Systems Research Laboratory at AT&T Bell Laboratories,
and has also designed, tested, and installed color television broadcast
equipment for the CBS Television Network Engineering and Development
Department. He has authored over 35 research articles in scientific journals in
physics and computer science, including Scientific American. If you have any
comments or questions about the article, you can contact him at dtso.info@displaymate.com.
About DisplayMate Technologies
DisplayMate Technologies specializes in 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
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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.
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