Tag Archives: technology

Shopping for a tablet this holiday season? Don’t forget to look at color performance

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If you have been researching the perfect tablet to give to a loved one this holiday season, you’ve probably read a lot about display quality. Tablet display size, resolution and aspect ratio have been discussed at length this year, which is really no surprise, since the quality of the display has the biggest impact on how we enjoy content on these devices.

What is surprising though is that color performance, one of the biggest differentiators among the current crop of tablet displays, has been largely glossed over by the mainstream gadget press.

The Verge’s tablet comparison tool, for example, gives great info about pixel density, aspect ratio and touch capabilities, but color performance is nowhere to be found:

Color is being ignored in spite of the fact that there are tremendous differences in the color performance of each of these devices that directly impact the consumer experience on each.

So why are we overlooking a feature that, unlike many of the features we focus on these days, presents a real difference between devices?  I see a couple reasons. First and foremost, thanks to Apple’s marketing of the Retina display, pixels-per-inch has become the spec du jour in today’s device wars.  Device makers are focusing their marketing efforts on pixel count above anything else.

Aside from current trends, I believe there’s also a macro reason to why color has been left out: color performance is just hard to compare. There is no universally accepted spec that can sum up color performance across devices.

Take the three popular tablets above. We could add a “color gamut” row to the chart, measuring against sRGB, which would look like this:

From this information, a shopper could gather that the Nexus 7 and Kindle Fire HD have about the same color performance and both outdo the iPad mini. That is an accurate assessment, but it’s not the whole story. If we look at those color gamuts plotted in CIE 1976, some important nuances become apparent.

By measuring the percent of sRGB, we know how much of that overall color standard the device can reproduce.  However, displays usually produce more of one color than another and that information is completely lost with this measurement.  The Nexus and Kindle have significantly deeper blue than the iPad mini, most likely due to a narrower blue color filter like the one found in the third and fourth generation iPad. This accounts for most of the difference in sRGB coverage between the iPad mini and the other two devices.

Take a look at the other two primaries and it gets more interesting. In the image on the right that zooms in on green, we see that the Kindle Fire has the deepest green of the three, followed by the iPad mini and the Nexus.

For reds, though, it’s different again, with the Nexus having the deepest reds followed by Kindle and then iPad.

If we ever want to make color performance a real differentiator in consumer choice, we need to develop a new universal standard to easily compare color across devices, taking into account all of these nuances.

Color is a complex story to tell, but small differences in color performance are just as noticeable to consumers as pixel density in everyday use. Next time you find yourself at a retailer who carries all three devices, try googling test patterns and look at the differences. You might be surprised.

Gizmodo: Tech’s New Most Meaningless Spec: PPI

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source: Gizmodo

Adrian Covert of Gizmodo has an interesting piece looking at the gadget industry’s recent obsession with high PPI displays. With devices like the HTC DNA pushing resolution well past 300 PPI, electronics makers may be turning PPI into the next overhyped marketing stat, just like contrast ratio is for the TV industry and megapixel is for the digital camera.

Adrian gets to the heart of the problem:

There are plenty of ways to make a better-looking display. But we’ve reached the point in the pixel density wars where higher figures have stopped automatically equating to improved performance for users. Any grandstanding about pixel density, from here on out, now is mostly just marketing fluff.

We tend to agree, and color performance is probably the display feature with the most room to improve. The best LCD smartphones on the shelves right now can show you more pixels than your eye can detect, but can only show you about a third of the colors you can see. If electronics makers want impactful feature improvements for new devices, color performance is where it’s at.

DisplayDaily: Is quantum dot lifetime good enough for TV?

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Ken Werner of Display Central has a post comparing the benefits of quantum dots to OLEDs in consumer TV applications.  Being the authority on quantum dot displays that we are here at Nanosys, Ken contacted us for an analysis.  Here is the explanation our Ph.Ds gave Ken:

OLEDs use organometalic compounds to emit light. They typically have a central metal atom surrounded by organic ligands. The decay issues are the same as with typical organic fluorophores.  In the excited state these molecules are very reactive to H2O and O2, as well as other small molecules that may be around. Once they react they become a different molecule and they will no longer fluoresce or phosphoresce and give off light. The more blue the light emission, the higher the energy of the excited state, and the more reactive the excited molecule will be. So your blue organic phosphores will have a much shorter lifetime than will red phosphores. The burn-in problem seen in OLED displays, that can be seen after just several weeks of operation with static content, is a manifestation of early blue degradation compared to green and red.

Conventional phosphores like YAG are doped materials. YAG used in white LEDs is actually cerium doped YAG. The cerium atom emits the yellow light and is surrounded by a vast amount of YAG. Quantum dots are similar in that a central core crystalline semiconductor material is used to confine the holes and electrons of the exciton (analogous to the cerium in YAG), and in our material this is surrounded by a thick shell of a different, lattice-matched semiconductor material (analogous to the YAG.) We call this a core-shell Quantum Dot structure. If the lifetime of our materials is less than that of conventional phosphors, it is typically because we have not made a perfectly lattice-matched shell, which may distort the core and cause defects at the core/shell interface that reduces the quantum yield.

The big difference here is that a perfectly made core-shell quantum dot does not have an intrinsic lifetime failure mechanism, whereas the organometallic compounds are intrinsically reactive to their environment, which makes them prone to shorter lifetimes especially at higher energies such as blue.

This is an important discussion, because TVs are a harsh environment for display components, running much hotter and brighter than tablets or mobile phones.  You can read the entire post here: http://www.display-central.com/flat-panel/is-quantum-dot-lifetime-good-enough-for-tv/

Updated: How does the iPhone 5’s color saturation measure up against Apple’s claims?

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Commenter William thankfully double checked our math and we’ve corrected a small error in our % NTSC calculation.

We finally got our hands on an iPhone 5 yesterday. I tried asking Siri if she really has 44% more color saturation but she wouldn’t give up the goods, so I went with plan B and aimed our PR-655 spectroradiometer at the phone to find out just how impressive the screen really is. A lot has already been written about this display, but not much empirical evidence has been published about the color performance. How does the screen actually stack up to the marketing claims?

In short, Apple did an exceptional job improving color saturation and display quality in general, but the unit we measured just missed the 44% more color saturation claim.

Measuring Up

The iPhone 5 has significantly more color saturation than the 4S.

The 44% more color claim for the iPhone 5 is the same claim Apple made for the new iPad. As with the iPad, increasing the color performance of the iPhone 4S by 44% of NTSC 1953 gamut, measured using the CIE 1931 color space, would result in color saturation matching the sRGB color standard.  Using these standards as the goal posts, we measured the iPhone 5 at 70% of NTSC 1953 in CIE 1931, a 39% increase from the iPhone 4S, which measured at 50%. That’s 5% less of an improvement than Apple’s 44% claim and just 99% of sRGB (measured against the sRGB primaries).

While 5% less might seem like a big deal, getting to 99% of sRGB is a major feat and will result in tremendously noticeable color improvement in the phone. Additionally, color filters are notoriously difficult to manufacture. Slight variances in performance like this are common and most likely outside the range of a just noticeable difference for the average person.

If you want to know more about NTSC, CIE and sRGB, and why we are using standards from the 1930s, I have written extensively about this issue in the past.

How did they do it?

Much like they did with the new iPad, Apple significantly improved the color filter performance† of the iPhone 5. Based on our experience, this type of improvement typically means that the display requires 20-30% more power to operate at the same brightness. Considering that the display is already a major source battery drain on the phone, this further underscores the engineering effort Apple made to keep battery life about the same as the 4S.

Let’s take a quick look at the changes in each of the red, green and blue color filters, starting with white, which is all three filters turned on:

Looking at the white spectrum of the iPhone 5, we see that the new color filters are very similar to those of the new iPad. Compared to the 4S, the peaks are slightly narrower, which improves color purity. In order to meet sRGB, they also moved to deeper reds and blues.

As with the new iPad, the biggest difference between the 4S and the 5 is in blue. Apple moved the peak to a deeper blue but, more importantly, they narrowed the filter so less green light leaks through. The green leakage causes blue to look a bit “aqua” on the 4S.

Retinal neuroscientist Bryan Jones looked at both displays under his stereo microscope earlier this week. His close-up shots really show off the difference in blue filters.

Apple again chose a slightly deeper wavelength of green which is less yellow and eliminated some of the blue leakage that had been muddying the green on the 4S.

The change here is subtle but as with the other filters, the peak is narrower, deeper in the red and leakage is reduced. One difference worth noting is that, while we are seeing less peak leakage in the red filter, there had been relatively broadband leakage across yellow, green and into blue that has been largely eliminated.

Conclusion

In all, it’s an exceptionally well-calibrated and accurate display for any kind of device, especially a smartphone. Apple has gone to great lengths to design a screen that brings the vibrancy of sRGB to the palm of your hand.
† If you are not familiar with color filters or the inner-workings of LCDs in general this great live teardown by Bill Hammack is well worth watching: http://youtu.be/jiejNAUwcQ8

iPhone 5 color saturation claims

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Display improvements were once again featured at yesterday’s Apple keynote event. The most obvious improvements may have been the larger display and thinner form factor but most interesting to dot-color are the color claims.

Just like the new iPad, Apple claims that the iPhone 5 can display “44% more color saturation.”

Apple SVP of Worldwide Marketing Phil Schiller talks color saturation at the iPhone 5 keynote

Let’s do some simple math to see how the iPhone 5 stacks up against older iPhones and last week’s color performance claim from Motorola.

  • iPhone 4S IPS LCD: 50% NTSC color gamut (CIE 1931†)
  • iPhone 5 IPS LCD: 50% * 144% = 72% NTSC color gamut (CIE 1931)
  • Motorola Droid Razr Maxx HD AMOLED: iPhone 4S (50%) * 185% = 92.5% NTSC (CIE 1931‡)

So Motorola is still king of the fall 2012 smartphone color saturation, based solely on marketing claims. That said, I wouldn’t be surprised if they updated their marketing to say that the Droid Razr Maxx HD offers 28% more color saturation than the iPhone 5 once it hits store shelves in a couple weeks. I plan to measure all of the announced devices to verify these marketing claims, but for now, this is all we have to go with.

Apple also claimed to be able to match the sRGB standard used in TV and movies. With the addition of the iPhone 5, nearly all of Apple’s flagship products (with the exception of the MacBook Air) now meet this standard. This means content should look very consistent across all Apple devices and may open up the possibility for serious content creation apps in iOS.

It also means we’re only just now catching up to an average CRT display from circa 1990, as the sRGB standard is based on the capabilities of phosphor materials used in CRTs. And even still, the new displays are only covering about 35% of the range of colors a human eye can see. There’s still plenty of room for improvement in display color performance (as well as updated content delivery standards, but that is a whole different post).  Hopefully if we keep on this kind of pace with display enhancements, next year we’ll start to see a push beyond the limits of last century’s color standards.

† We’re using the long outdated CIE 1931 color space and NTSC 1953 gamut standards here since this is clearly Apple’s reference when they claim 44% more saturation and sRGB coverage. 50% * 1.44 = 72% and 72% of NTSC 1953 gamut in the CIE 1931 color space is also called the sRGB color gamut.

‡ It is not clear which color space Motorola is referencing; we are assuming CIE 1931/NTSC 1953 for ease of comparison.

Beyond Retina: holiday releases see device makers move beyond PPI in display marketing efforts

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Over the past couple weeks we’ve seen device manufacturers start to gear up for the holiday season, highlighted by big product announcements from Nokia, Motorola and Amazon. It’s been especially interesting for me to follow how these companies market the most important part of the device – the screen. While pixel per inch still seems important, device makers have moved into more nuanced territory, highlighting deeper features like reduced reflectivity, improved touch sensitivity and color saturation.

Here’s a roundup the most interesting new display features in this holiday’s hottest devices:

Nokia was first up this week with a new crop of Lumia handsets, the 920 and 820. They introduced a slightly larger display for the flagship 920 (now 4.5 inches compared to last year’s 4.3” Lumia 900), touted a new level of touch sensitivity that even works with gloves and claimed 25% more brightness than rival phones. Also of note, they switched from AMOLED to IPS LCD. It’s not yet clear if cost/supply issues or performance drove this switch. It may be that they preferred the brightness and power efficiency of LCD.

Right on the heels of Nokia, Motorola and Google announced a group of new smartphones, led by the Droid Razr Maxx HD. The company described the new Super AMOLED display as having “85% more color saturation than the iPhone 4S, so everything is in lifelike detail.” It’s great to hear them talking about the value of color performance. Hopefully they’ve included some color rendering optimization to artfully take advantage of that extra saturation without overdoing it.

Amazon followed up yesterday with several new devices across their entire Kindle line-up and a surprisingly technical presentation that took a deep dive into the LCD film stack. They showed how a reduced air gap between the touch screen and LCD surface can reduce screen glare, suggesting the new Fire HD has reduced glare by 25%. Also, in a move that’s sure to please LCD film manufacturers like 3M, they discussed the value of better polarizing filters for achieving wider viewing angles without color distortion.

Of course, everyone still compared their products to the now year old iPhone 4S, so it will be interesting to see how these features stack up to whatever Apple introduces next week.  We’ll be sure to pick up a few of these devices and run them through their paces to see how the marketing-speak stacks up to real world performance.