How much color gamut do displays really need? Part 2: How we perceive color

Last week I set out to define the ultimate consumer display experience in terms of color performance. I laid out some potential color performance design goals for an ideal display, suggesting that such a display should be both accurate and capable of creating an exciting, immersive experience that jumps off the shelf at retail.

Can we achieve both goals? To find out, let’s start by looking at how we perceive color.

Color Perception

The color of objects that our eyes see in nature is determined by three things: physical, physiological and psychological:

The color of objects that our eyes see in nature is determined by three things: physical, physiological and psychological.

The color of objects that our eyes see in nature is determined by three things: physical, physiological and psychological.

The physical component of our color perception is a constant based on the laws of nature. It is a combination of the quality of the illumination or light source, in this case meaning spectrum it contains, and the reflectance of the object. In the image above, the ball appears red to the eye because it is reflecting red light, while absorbing most the other colors from the light source.

The physiological part of our vision is also a relative constant that is based on the electrochemical processes of the eye. The back of the retina contains photoreceptor nerve cells which transform incoming light into electrical impulses. These electrical impulses are sent to the optic nerve of the eye and onto the brain, which processes and creates the image we see. And that’s where the psychological component comes in.

Let’s look at how each of these components might affect display color performance, starting with the physical, which ought to be something we can measure.

Physical

Fortunately, a guy named Pointer has done this for us. For his 1980 publication, Pointer measured over 4,000 samples and was able to define a color gamut of real surface colors, of objects found in nature. The result is commonly called “Pointer’s Gamut:”

Color gamut of 4,000 surface colors found in nature as measured by Pointer in 1980 against the color gamut of the iPhone 5.

Color gamut of over 4,000 colors found in nature as measured by Pointer against the color gamut of the iPhone 5.

This already seems like a great place to start. It immediately looks like a great fit our first ultimate color experience criteria which was accuracy. If we could accurately capture and reproduce all of the colors found in the natural world it would make for a much improved, more accurate ecommerce experience, for example.

But how important are those extra colors? Looking at Pointer’s gamut mapped against the color gamut of the latest iPhone in the chart above, you have to wonder if we really come across these deep cyans and reds in everyday life. Are they just infrequent, rare colors or something worth pursuing for our display?

Turns out we do. As an example, Pantone’s color of the year for 2012 was a deep emerald green that falls outside of both the iPhone’s gamut and the HDTV broadcast standard. This is an important and popular color that appears a bit too yellowish on your computer monitor when you are shopping for the perfect tie on Amazon. So there are some really important colors outside of what the iPhone can display today.

But, what about our second criteria, the lifelike, exciting, immersive experience we want to give consumers? Is the gamut of the natural world enough?

Physiological

If we look at the second component of the visual system, the physiological component, we’ll see that we can actually perceive a much wider range of colors. The cells in the back of retina can actually detect the entire range of the CIE diagram. That’s almost double the range of colors that Pointer found in nature:

Color gamut of the average human eye vs gamut of colors found in nature as measured by Pointer

Color gamut of the average human eye vs gamut of colors found in nature as measured by Pointer

This is starting to sound like a much more immersive experience. Maybe we ought to pursue the full color capability of the human eye just like the industry has done for high, “retina” resolutions.

It sounds great but it would be a tall order. It would take quite a lot of power, brightness and extra bit depth to even begin to think about covering a color space this large. There certainly would be a high price to pay in terms of design tradeoffs to get there. So are there any truly valuable colors contained in that extra space, similar to the Pantone color in Pointer’s gamut, that would make us want to go for it?

Psychological

This is where the psychological component comes into play.

Seeing is not passive. Our brains add meaning to the light that our eyes detect based on context and experience and memory. We are continuously and actively re-visualizing the light that comes out of our retinas.

This may seem hard to believe but this fun demo created by neuroscientist Beau Lotto does a great job of showing just how much our brains actively interpret and change what we see.

The color of the chips has not changed in the video above, just our perception of the color. What’s happening here is our experience is telling us that the color chip in shadow must actually be a much brighter color than the chip under direct illumination, so our brain is just making the correction for us on the fly.

Artists absolutely play on this psychological element of our perception of color, sometimes using totally unrealistic or hyper real colors to make us feel or experience something new or help tell a story. In fact, one of the most influential art instructors of the 20th century, Josef Albers, once said that, “the purpose of art is not to represent nature but instead to re-present it.”

Monet's The Poppy Field, near Argenteuil

Monet’s The Poppy Field, near Argenteuil

So, whether it’s Monet using saturated and contrasting colors with equal luminance to trick our brains into seeing poppy flowers sway in an imaginary breeze in a 19th century painting or modern films which sometimes rely on the wider gamut capabilities of color film and digital cinema projection to create uniquely cinematic experiences for audiences.

Movies like “The Ring,” for example, which used a deep cyan cast throughout much of the film to create tension and help tell a scary story. Or Michael Bay’s “Transformers” movies, which use deeply saturated oranges, reds and teal greens to create an exciting, eye-popping palette appropriate for a summer blockbuster sci-fi movie about giant robots:

Wide color gamut in movies

There’s certainly a place for wild, unexpected colors in art. But, as we go through some of these examples, I think we’ll actually find that there is a huge range of expression possible within the gamut of surface colors that Pointer measured. The full range of gamut detectable by the human eye, while exciting to think about, is not really necessary to deliver both accurate and pleasing (engaging) color to our visual system.

So where does that leave us?

In my next post I’ll look at existing wide color gamut standards and content delivery mechanisms to see both what we can do today and what’s next for wide color gamut displays.

How much color gamut do displays really need?

In my last post, which focused on the trend towards ever higher resolutions in smartphone displays, I suggested that color performance might be a more useful area of focus for display makers. That’s because, in terms of color gamut, we are a long way from reproducing the full range of colors that our eyes can detect.

For context, let’s add the color gamut of one of the most popular smartphones on the market, Apple’s iPhone, to the chart from my last post:

Best performing smartphones in resolution vs iPhone color gamut performance since 2009.

Best performing smartphones in resolution vs iPhone color gamut performance since 2009.

The latest iPhone only covers about 1/3 of the range of colors our eyes can detect so we’re a long way from matching the acuity of the best displays on the market in terms of resolution. But, how much color do we really need for a great experience?

As a display technologist and color blogger that’s probably the question I’m most frequently asked. If I’m advocating for more colorful displays, how much more am I after? There’s got to be a reasonable limit right?

Perhaps unsurprisingly, the short answer is that it depends on a lot of things. Different applications, from ecommerce to the TV on your living room wall, all require differing amounts of color performance. The environment matters a lot too, if the display will be used outdoors brightness may be a factor. There are slowly evolving broadcast standards and content delivery infrastructure to consider as well. And, of course, technology limitations– what can be achieved today and at what cost?

These are all valid concerns for anyone designing and marketing a new display product but they don’t really answer the bigger question. To me, what we really ought to be asking here is: what would the ultimate consumer experience be in terms of color? To answer that, I think we first need to take a step back, put some the practical stuff aside for the moment, and define what that experience should look and feel like. Once we understand that we can start to put the technological pieces together to achieve it.

What do we want?

So, let’s first ask: what do we want? In a pie in the sky, ideal display, in terms of color performance?

Well, the engineers among us are probably thinking, first and foremost, it has to be accurate and that’s a great place to start. Our displays need to accurately reproduce colors found in nature for increasingly important ecommerce applications, photos we take of our family should look real, not over saturated and professionally created content should be reproduced so that it conveys the artist’s intent without distortion.

But, maybe the marketing folks among us have another criteria in mind and that is a bit more subjective. We want our displays to be immersive and engaging. We want them to jump off the shelf at retail and we want to deliver a unique and exciting experience to our customers.

Can we have both?

To find out, I’ll be taking a look at how we perceive color in my next post.

 

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.

DisplayWeek 2013: Color is back

Just back from a great DisplayWeek in Vancouver. Finally had a chance to recover, go through my notes and process everything I saw at the show. Most of the big story lines will be pretty familiar to anyone who followed last years show: TV’s are still getting bigger, OLED TV is still right around the corner, 4K is starting to ship and mobile displays are getting both sharper and more efficient.

DisplayWeek wasn’t all old news though. In fact, just like CES, this year everyone seemed to be talking about color performance. At the annual Display Industry Awards, honors in several categories went to wide gamut display technologies including the Best In Show and Component of the Year awards. And, on the show floor, major manufacturers like 3M, Samsung and LG dedicated significant booth space to wide color gamut or color management technologies.

3M's Quantum Dot Enhancement Film demo at DisplayWeek 2013. Bottom display is using quantum dots to achieve a wide color gamut.

3M’s Quantum Dot Enhancement Film (QDEF) demo at DisplayWeek 2013. Bottom display is using quantum dots to achieve a wider color gamut than OLED at higher brightness and lower cost.

3M demoed several wide color gamut LCDs  based on the Quantum Dot Enhancement Film (QDEF) technology that they are partnering with Nanosys to manufacture. Ranging from smartphone all the way up to 55″ TVs in size, these devices were all showing a wider color gamut than OLED with an especially deep red. This seems like a lot of color but 3M says that in developing their Perceptual Quality Metric (PQM), a new analysis tool aimed at helping display makers model how different performance characteristics will affect end user experience, they found that color saturation positively affected the perception of quality.

In Samsung’s neighboring booth, I found a series of comparison demos designed to show that wide color gamut displays can be both accurate and pleasing to the eye. Each demo featured a camera feeding a live image of several colored objects to both standard and wide color gamut displays. In each case the wide gamut display was able to more accurately recreate the color of the objects in front of the camera. They also showed off the new color management capability of their flagship Galaxy S4 smartphone that allows the device to accurately display rec.709 content without oversaturation- something the previous generation S3 struggled with.

Samsung demonstrating the value of wide gamut displays by showing some common colors that fall outside the rec.709 broadcast gamut standard in a series of demos at DisplayWeek 2013

Samsung demonstrating the value of wide gamut displays by showing some common colors that fall outside the rec.709 broadcast gamut standard in a series of demos at DisplayWeek 2013

Finally, at LG’s booth, we saw a new LCD color filter design that allows them to cover the Adobe RGB color gamut used by photographers and print professionals.

With all of this buzz, it looks like we’ll start to see wide color gamut displays start to move into the mainstream in ever larger screen sizes over the next half of this year and into 2014.

Color and Visceral App Design

Visceral refers to the gut, rather than the mind. Our brain may try to talk us out of jumping off a cliff, but as soon as we take that first step into the void, our guts take over. We respond with a rush of emotion and we can’t help but scream from terror or euphoria. It’s a purely visceral reaction. […]

So here’s my theory: I believe that introducing visceral elements into an app will take it past the point of just being awesome. It will make your app speak to the subconscious, built-in affinity that humans have for the physical properties I mentioned before.

That’s Rob Foster, co-founder of Mysterious Trousers, defining his theory about the importance of visceral elements in application design. The whole piece is well worth reading, especially if you are interested in design or have ever wondered just why Angry Birds is so unbelievably addictive.

In the quote above Rob is talking about the power of little kinetic events in applications like the bounce you get when scrolling to the bottom of a page on the iPhone or the satisfying little “pop” noise you hear when creating a new task in Clear. His point is well made, getting the details of these visceral elements right can clearly take an app from just useful to a truly engaging and even addictive experience for users.

While Rob’s piece focused on the impact of animation and sound, I wondered how color might factor into visceral application design.

Color choice is not just about beautiful graphics- it can also have a powerful physiological effect on us. We have a measurable response to aggressive colors like red, which may even cause a spike in testosterone levels. In fact, recent studies suggest that that the color of a uniform can affect the outcome of an Olympic wrestling match and onscreen colors can even influence how much you pay for something on eBay.

As mobile display technology improves, with more lifelike color and wider dynamic range, application designers may find that color becomes an even more powerful tool to elicit visceral responses from users.

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. 

ITU agrees on HEVC h.265 codec

h-265-logo,Q-D-349573-3The ITU announced today that it’s members have agreed upon a new high efficiency video codec. Dubbed HEVC H.265, the new format is designed to improve on and ultimately replace the current king of all codecs, H.264/MPEG-4 AVC which covers 80% of internet video today.

So far, a lot of attention has been given to the codec’s ability to deliver the same quality video as 264 with only half the bandwidth. That kind of efficiency improvement is a big deal– it could reduce strain on networks and bring high-resolution 4K content delivery over the internet closer to reality.

h265 vs h264 quality comparisonThere are also some important changes for color in the new spec. Recent drafts by the ITU’s Joint Collaborative Team on Video Coding (JCT-VC) have added support for wider color gamuts like Adobe RGB 1998 and 12-bit video. This paves the way for fantastic looking color as wide gamut-capable hardware starts to become more widely available.

Color at CES 2013

I’m just wrapping up my visit to CES and it’s been interesting year for display technologies. Amid all the noise about 4K, OLED and 4K-OLED, color performance seems to have quietly worked its way into the conversation. I can’t recall ever having so many relatively technical conversations about color with booth reps from major consumer electronics manufacturers at a CES. It nearly started feeling like a visit to DisplayWeek, that is until I ran into some of the weird, only-at-CES iPhone cases

Color Your World CES 2013

I bet we’ll see more color talk next year, especially as 4K content delivery mechanisms and standards begin to mature. In the meantime, these are some of the color-related display stories that caught my eye this week:

Wide gamut content delivery

Sony’s 4K content delivery plans have been one of the most talked about topics here at CES. Less mentioned was Sony’s inclusion of wider color gamut in their standard. Sony reps that I talked to said that both the 1080P Blu-ray disc-based “mastered in 4K” and pure 4K delivery methods would include a wider color gamut. They were not ready to release specifics on gamut size or whether it would meet existing standards like DCI-P3. Still, bringing “expanded color showcasing more of the wide range of rich color contained in the original source” is a move in the right direction for wide gamut.

Color accuracy

Technicolor showed off a color certification program that they hope will incentivize display makers to improve the color accuracy of their panels. Displays that meet or exceed Technicolor’s color specs will get a badge and a copy of partner Portrait Display’s Chroma Tune software, which dynamically controls color gamut to match the application you are using. This means if you open Photoshop on a device with an Adobe RGB 1998 capable display, you’ll get the full, wide gamut. But, if you switch over to watch a YouTube video in your browser, the software will limit the display to rec.709 for the most accurate experience. The advantage was well demonstrated by their e-commerce demo, where a pair of shoes were more accurately depicted on a certified display:

Technicolor's ecommerce Color Certification demo at CES 2013. The color certified laptop in the middle of the frame more accurately shows the color of the shoes.

Technicolor’s ecommerce Color Certification demo at CES 2013. The color certified laptop in the middle of the frame more accurately shows the color of the shoes.

Like Sony’s upscaling effort, this kind of technology could help drive wide color gamut adoption by making today’s content compatible with newer displays.

Huge tablets

Panasonic 4K Tablet with sRGB color gamut at CES 2013

Panasonic’s 20 inch 4K/sRGB tablet

Several companies at the show introduced devices in a new class- the 20-plus inch tablet. While there were a lot of hokey multi touch gaming demos (are you really going to play poker with 4 smartphones and a 27″ screen instead of a deck of cards?), the content creation stuff Panasonic showed actually made me think the new form factor shows real promise as a professional tool.

Their tablet, which measures 20 inches on the diagonal, features a 4K IPS panel that covers 100% of the sRGB color gamut standard. Having such a a large canvas with high resolution, accurate color and multi-touch could be great for creative pros like photographers and architects.

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.