Smartphone displays continue to get sharper- how much resolution do we really need?

Last week DisplaySearch put out a new report on the current trend towards ever higher display resolutions. High resolution displays now make up most of the market for handhelds and 300+ ppi “retina-class” resolutions are coming on strong:

Smartphones and handheld devices are moving rapidly to high resolution. 200+ ppi will account for 54% of unit share in in 2013, with 24% of unit share to be 300+ ppi. Even higher resolution panels in the FHD class will emerge. 400-500 ppi FPDs are expected to hit the market with fast shipment growth in 2013. (source: DisplaySearch)

Not exactly earth shattering news. The display industry began rapidly moving towards higher resolutions the moment Apple first unveiled the retina display with it’s iPhone 4 in 2009. What is interesting here is that the trend shows no signs of abating, even as resolutions approach or surpass the acuity of the average human eye.

Highest resolution smartphone from 2009 to 2013 as a percentage of what the human eye can detect

Best performing smartphones in terms of display resolution from 2009 to 2013. Shown as a percentage of what the average human eye can detect.

The HTC One is leading the charge this year at 468 ppi. According to Dr. Ray Soneira of DisplayMate, that’s already equivalent to Apple’s retina display for eyes with 20/20 vision at a distance of just 7.4 inches from the eye- much closer than an average user will typically hold the device.

The question is- just how noticeable are additional increases in resolution beyond 400-500 ppi going to be for consumers? In my view, resolutions above 530 ppi will be wasted on the vast majority of users. Unless you have near perfect vision and hold your phone excessively close to your eye, you just won’t be able to see the difference. Still, device makers seem intent on pushing resolution as far as they can- some manufacturers I spoke with at DisplayWeek 2013 even talked about 4K smartphones!

It’s a shame because there are many other display performance characteristics that would benefit users. They may sound like less exciting specs but color performance, sunlight readability (a combination of reflectance, brightness and color saturation), and efficiency would all improve usability much more than another 50 or 100 ppi in resolution.

Adobe’s Kuler color app is a great tool for designers but is your display accurate enough for it?

Screenshot of Adobe's Kuler app showing color extraction from a photo

Screenshot of Adobe’s Kuler app showing color extraction from a photo

Adobe recently released a new iPhone app called Kuler that let’s you extract colors from your surroundings using the phone’s camera. It’s a useful tool that allows designers to capture color inspiration wherever they find it and easily incorporate it into their work via color palettes.

The app also highlights a weakness in current display technology: no display on the market today can actually reproduce all the colors we see in the environment around us. So, even if the camera sensor can capture that color you love, you may not be seeing an accurate representation of it on your device.

The iPhone 5’s LCD display is designed to cover the sRGB/rec.709 color gamut standard used for HDTV broadcasts. And, it looks great but compared to the world we see around us, it’s just not quite as rich. If we plot the iPhone 5’s color gamut against the gamut of colors found in nature, the phone comes up short in important reds, greens and cyans:

Color gamut of the iPhone 5's display compared to the gamut of colors found in nature. The iPhone 5 comes up short in red, green and cyan.

Color gamut of the iPhone 5’s display compared to the gamut of colors found in nature. The iPhone 5 comes up short in red, green and cyan.

If DisplayWeek 2013 was any indication, color has once again become a hot topic in the display industry. Color gamuts are getting larger and it may not be long before we see a display that can match what our eye sees in nature. Over the course of the next year, we will start to see more wide color gamut-capable devices as OLED continues to expand marketshare and new technologies like quantum dot LCD begin to enter the market in volume.

Apple CEO Tim Cook talks color quality at Goldman Sachs conference

Apple CEO Tim Cook

Apple CEO Tim Cook spoke at Goldman Sachs’ Technology and Internet Conference yesterday. He touched on a wide range of topics from what Apple plans to do with its cash horde to the state of its retail operation. When it came to a question about making lower cost products, Tim used display quality to help make a point about creating great user experiences:

The truth is, customers want a great experience and they want quality and they want that a-ha moment each time that they use the product, and that’s rarely a function of any of those things.

If you look at displays, some people are focused on size. There’s a few other things about the display that are important. Some people use displays, like OLED displays, the color saturation is awful. And so if you ever buy anything online and you want to really know what the color is as many people do, you should really think twice before you depend on the color of the OLED display. The Retina display is twice as bright as an OLED display. I only bring these points up to say there are many attributes to the display, and what Apple does is sweat every detail.

He makes some fair points here. If a display is not bright enough to view in all conditions, not efficient enough to get you through a whole day or accurate enough to display your favorite content, the experience of the whole device suffers. Choosing the right display technology is certainly a critical part of the design process.

OLED technology’s power consumption and saturation issues have been well established already. What I find most interesting in Tim’s comments is the idea that high color saturation is intrinsically a bad experience. It certainly has been that way so far but the difference between a great color experience and the gaudy oversaturation of today’s OLEDs is in exactly the kind of implementation details he’s describing above.

OLED and emerging LCD technologies, like quantum dot displays, can actually show a much wider range of colors than today’s devices– over 40% more of the color that our eyes can detect. This means that, when paired with the right content, high saturation displays can more accurately reflect the world we see around us resulting in a more lifelike, immersive experience.

But how do we get wide color gamut content into consumers hands?

It’s a lot like the chicken and egg/content and technology dilemma facing 4K TV makers with two key differences- wide color gamut can be delivered with no change in file size and there’s plenty content out there already. As an example, movies have been shot for decades on media, both film and digital, that has a much wider color gamut than your TV does today. Much in the same way that 4K TV’s can upscale HD video, it’s also relatively easy to manage the color on a device to make it backwards compatible with today’s content.

OLED implementers have thus far been content to take advantage of the extra pop that added color saturation provides when comparing devices on a store shelf. They’ve left a tremendous amount of overall ecosystem value on the table. It’s possible to deliver video in cinema-level color quality to mobile devices, to offer developers the tools to take full advantage of a wider color palette and to implement accurate color management for existing content. Wide color gamut is ready now, it’s just waiting for the right device maker to come along and put all these pieces together to perfect the experience. 

Are tablets up to the task of accurate color testing?

Finally getting around to posting a follow-up to a follow-up to John The Math Guy’s recent series on color gamut size, colorblindness and tablet displays. I thought I might be able to at least shed a little more light on his question about the differences in color accuracy between some of these devices.

In his testing, John found no statistically significant difference in scores among different people taking the EnChroma colorblindness test on different devices. I found this somewhat surprising since, in my experience, even tablets with similar color gamuts tend to show colors with very different levels of accuracy.

iPad mini color gamut and Gretag Macbeth colors against sRGB in CIE1976

To show what I mean by that, I measured how two different tablets show the colors found in the Gretag Macbeth color checker chart.Nexus 7 color gamut and Gretag Macbeth colors against sRGB in CIE1976

As you can see, the iPad mini and Nexus 7 each produce very different colors, even for those colors that are actually inside their gamuts.

For example, even though the iPad mini has enough gamut coverage to accurately display the Gretag chart’s deepest blue, it cannot do so without distorting the image in another way. This is because of data in the underlying image standard- most content today is encoded in the sRGB standard. If the iPad were to show that Gretag blue correctly, it would not have enough color saturation headroom left over to show you a different color if a deeper blue, say right at the bottom of the sRGB triangle, were called for.

A good real world example of this can be found in the picture below of my bloodhound, Louisa, racing down the beach at Carmel, CA. The middle of the sky in this image is right on the edge of the iPad’s color gamut, very similar to the Gretag blue in the charts above, while the deepest blues found in the ocean fall outside the iPad’s gamut.

Out of gamut colors at beach

If the iPad were striving for accuracy at all costs, it might map both colors right on top of each other at the edge of the gamut. There’d be no visible difference between the two in this case and the quality of the image would suffer but at least the sky would be accurate. In order to avoid this scenario, the designers of these devices have decided to compromise on accuracy so they can show a full range of color differences to the user.

They do this by remapping colors inward, away from the edges of the gamut, effectively compressing the gamut even further so that otherwise out-of-gamut colors can be seen. This is a good solution given the gamut limitations of the device since it results in more pleasing, if less accurate images.

As newer devices trend towards wider color gamuts this kind of compromise should become a thing of the past. In fact, tablet designers may be working on the reverse issue- how to avoid oversaturating images that were encoded for smaller gamuts.

Great, how does this relate to colorblindness again?

iPad mini vs Nexus 7 color accuracy comparison in CIE 1976

iPad mini vs Nexus 7 color accuracy comparison in CIE 1976

Taking another look at the Gretag results from the two devices plotted on top of each other, there clearly are major differences. But, in the reds and greens, two colors associated with a common form of color blindness, the devices are relatively close. So, the simple answer may just be that colorblindness tests do not require pinpoint accuracy to be effective, at least as basic screening tools.

Time to Ditch the Diagonal?

Size is a critical dimension for consumers to consider when buying a product with a display. Will this TV fit on my wall? Would this tablet fit in my jacket pocket?  How much picture am I getting? To guage displays today, we take a diagonal measurement of a 16:9 rectangle. This leaves value on the table. Not just because consumers are notoriously bad at math, it fails to capture the full value of the increase. As display industry analyst Bob Raikes said:

A display that has twice the diagonal (and the same aspect ratio) has four times the screen area. Would Intel describe the clock speed of its CPUs by giving them a number that is the square root of the clock speed? If Intel went from 1GHz to 2GHz, would the company really give customers a number that is just 40% bigger? Ah, we’ve gone from 1 IntelMark to 1.4 IntelMarks. No chance!

Why would we say “twice” when the real value increase is “four times”? This is especially relevant as consumers shop more online. Although size may be apparent in a brick and mortar showroom, it is not easily conveyed online. Take a look at this image- which tablet is bigger? By how much?

Apple’s Phil Schiller demonstrated this yesterday at the iPad mini announcement. The new iPad mini is only 0.9 inches or 12% bigger than a Nexus 7 on the diagonal, he says, but it is actually 35% larger by area. This is another example of display marketing efforts starting to move beyond PPI comparisons. Product and display marketers: let’s get real about the value we’re adding – whether it’s surface area or color. Let’s stop leaving value on the table.

Source: apple.com

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

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

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

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.

Seeing red: can color change your spending habits?

Color can have a powerful physiological effect on us. This should come as no surprise to anyone who’s ever been wowed by a Monet or a Rothko. But color can affect us in ways you never imagined. Recent studies suggest that that the color of a uniform can affect the outcome of an Olympic wrestling match and onscreen colors can influence how much you pay for something on eBay.

In one study, researchers found that Olympic wrestlers wearing red won as much as 60% of the time, even against evenly matched opponents (who wore a different color).

US Wrestler Jake Varner (red) on his way to defeating Valerie Andriisteve of Ukraine in the 96-kg freestyle wrestling gold match in London. Credit: The ASSOCIATED PRESS

Similarly, in a Journal of Consumer Research study on the impact of color on consumers who buy items on auction sites like eBay, authors Rajesh Bagchi and Amar Cheema found that “red background color induces aggression through a feeling of arousal and it increases aggression relative to blue or gray backgrounds. This causes individuals to make higher bids in auctions but lower offers in negotiations.”

Why? The exact mechanism remains a mystery but researchers see some evidence that aggressive colors like red may actually cause a spike in testosterone levels.

I find it particularly fascinating that color choice did not specifically correlate to the price someone paid for an item. Instead, the colors drove more or less aggressive behavior, which lead participants to either seek the best deal possible against a salesperson or to beat out competing bids in an auction.

It got me wondering how retailers might be using color to influence purchasing. A quick survey of some popular online shopping destinations yielded potentially interesting results. Since product background is not always in the control of the retailer, I looked at the “add to cart” areas of three popular online retailers: Apple, Amazon and eBay.

All three employ a lot of blue, a calming color, in their ‘add to cart’ areas. Apple uses a shade of green, another calming color, for the “add to cart” button. Amazon lists the price in a dark red, while Apple uses a lighter shade to accentuate free shipping.

Next time you find yourself shopping either online or brick and mortar, take note of the colors around you – you may be surprised by how far your environment is being manipulated to get you to pay more.

Is creativity the next killer mobile app?

Since the debut of the iPad in 2010, tablets have become the ultimate content consumption device, but many still to wonder if they’ll ever be capable of replacing notebooks for portable content creation.

While tablets may never truly replace notebooks for all of our content creation needs, especially typing intensive ones, a new crop of apps for iOS and Android are certainly making a case for it.

A little doodle made with the glorious new #Paper app for the iPad from @FiftyThree

(via Brian Taylor from CandyKiller: A little doodle made with the glorious new #Paper app)

Recent creative apps like Paper by fiftythree, Adobe’s Photoshop Touch and Apple’s iPhoto for iOS have just started to scratch the surface of the creative capabilities of powerful mobile devices. These apps show us that mobile creativity, when done right, can harness the unique properties of a touchscreen handheld device to offer new capabilities that a laptop cannot duplicate. Drawing with a stylus in Paper, for example, feels remarkably precise and expressive because of a neat gesture trick- the speed of your pen controls the thickness of the line. Similarly, in Photoshop Touch and iPhoto, editing your photos by actually putting your hands on them, while less precise than a keyboard and mouse, can be a revelation for broad stroke tasks like blending two images.

Tablets clearly have the processing power, the battery life and display resolution necessary to become serious creative tools, but there’s one thing missing: color. Creative professionals normally work on displays capable of showing a range of colors that is as much as 60% wider than even the latest “high color saturation” iPad. Artists need to see the content they are creating in the same vibrant colors they see in the real world.  Improving the color performance on mobile devices will make tablets truly worthy of a place in any creative professional’s regular workflow.