Tag Archives: color saturation

How much color do displays really need? Part 4: Content Delivery

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In the previous post in this series, I made the case for displays with hybrid, custom color gamuts as a great way to deliver coverage of Pointer’s gamut as well as the most important broadcast standards. We can build the hardware today to support these large color gamuts so its seems like a great solution but there is a catch: nobody is broadcasting or distributing these large color gamuts today. So, are we going to have to wait for broadcasters and content creators to slowly catchup, much like we did with HDTV?

What content delivery looks like today

Content is captured and viewed in a wide variety of gamuts across a range of different devices but only broadcast in one gamut.

Content is captured and viewed in a wide variety of gamuts across a range of different devices but only broadcast in one gamut.

Today, content creators are actually shooting in a wide variety of color spaces ranging from RAW to rec.709 to Adobe 1998. They are then forced to cram all of these different sources into the lowest common denominator rec.709 standard for broadcast or distribution. That same content is then displayed on devices with a range of different gamut capabilities from tablets that only cover about 70% of rec.709 to HDTVs that do meet the spec to OLED devices that oversaturate the content.

There’s a lot of diversity on both the capture and display sides and a clear bottleneck in the middle in the form of broadcast and distribution channels.

Adhering to broadcast standards is no longer sufficient to guarantee a good experience for consumers because there’s already too much diversity on the display side alone to rely on one standard. You just can’t be sure that consumers are actually looking at your content on a rec.709-capable device. We’re also losing a lot of the value that creators are capturing and could, in many cases, be delivered to end viewers who have the devices to show it.

How do we get around broadcast standards?

What content delivery looks like tomorrow

The first thing to note is that the internet is democratizing broadcast and distribution channels. With the web we can deliver whatever we want, whenever we want. Some players in the industry, notably Sony, are already doing this with 4K content. If there’s no content available and you believe in 4K resolution, you just deliver your own content directly to your customers.

Wide color gamut displays combined with good quality color management and the web as a broadcast platform will allow content to accurately be displayed in the correct color gamut.

Wide color gamut displays combined with good color management and the web as a broadcast platform will allow content to accurately be displayed in the original color gamut.

Still, this leaves us with some potential experience problems. If the right display gamut is not matched to the right content the results will be no different and that’s why color management is key. There are several companies working on color management solutions and certification programs for devices that will make it possible for wide color gamut displays to handle a variety of incoming gamuts. Using metadata, for example, a wide color gamut display can be alerted to the presence of Adobe RGB content and then remap that content on the fly to assure that it is displayed accurately on that specific panel.

With great color management, we can maximize the gamut on the display side and pull through the best possible gamut for the device we are looking at. In this way, we can deliver always accurate content that meets the designers intent, wether artistic or commercial.

DisplayWeek 2013: Color is back

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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.

Apple CEO Tim Cook talks color quality at Goldman Sachs conference

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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. 

The case for wide-gamut in your photography workflow, even if you are exporting to sRGB

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This is a great, exhaustive tutorial on managing color gamut for photographers by color expert Andrew Rodney. He does a great job making the case for working in wide gamut color spaces like Pro Photo, especially when capturing in RAW. Using smaller gamuts like sRGB throws away useful color data that printers and more and more displays can recreate.

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.

Color Space Confusion

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For many who are new to the world of display measurement, the prevalence of two distinct, but often-interchanged color spaces can be a source of confusion. Since my recent post about the color performance of Apple’s new iPad, a number of people have asked about this topic, so I thought it would be worth a closer look.

In the world of displays and color images, there exists a variety of separate standards for mapping color, CIE 1931 and CIE 1976 being the most popular among them. Despite its age, CIE 1931, named for the year of its adoption, remains a well-worn and familiar shorthand throughout the display industry. As a marketer of high color gamut display components, I can tell you from firsthand experience that CIE 1931 is the primary language of our customers. When a customer tells me that their current display “can do 72% of NTSC,” they implicitly mean 72% of NTSC 1953 color gamut as mapped against CIE 1931.

However, from the SID International Committee for Display Metrology’s (ICDM) recent, authoritative Display Measurement Standard:

“…we strongly encourage people to abandon the use of the 1931 CIE color diagram for determining the color gamut… The 1976 CIE (u’,v’) color diagram should be used instead. Unfortunately, many continue to use the (x,y) chromaticity values and the 1931 diagram for gamut areas.”

So why are there two standards, and why are we trying to declare one of them obsolete? Let me explain.

What is a color space?

First, a little background on color spaces and how they work.

While there are a number of different types of color spaces, we are specifically interested in chromaticity diagrams, which only measure color quality, independent of other factors like luminance. A color space is a uniform representation of visible light. It maps the all of the colors visible to the human eye onto an x-y grid and assigns them measureable values. This allows us to make uniform measurements and comparisons between colors, and offers certainty that images look the same from display to display when used to create color gamut standards.

In 1931, the Commission internationale de l’éclairage or CIE (International Commission on Illumination in English) defined the most commonly used color space. Here’s a look at the anatomy of the CIE 1931 color space:

What makes a good color space?

An effective color space should map with reasonable accuracy and consistancy to the human perception of color. Content creators want to be sure that the color they see on their display is the same color you see on your display.

This is where the CIE 1931 standard falls apart. Based on the work of David MacAdam in the 1940’s, we learn that the variance in percieved color, when mapped in the CIE 1931 color space, is not linear from color to color. In other words, if you show a group of people the same green, then map what they see against the CIE 1931 color space, they will report seeing a wide decprepancy of different hues of green. However, if you show the same group a blue image, there will be much more agreement on what color blue they are seeing.  This uneveness creates problems when trying to make uniform measurements with CIE 1931.

The result of MacAdam’s work is visualized by the MacAdam Elipses.  Each elipse represents the range of colors respondents reported seeing when shown a single color, which was the dot in the center of each elipse:

A better standard

It was not until 1976 that the CIE was able to settle on a significantly more linear color space. If we reproduce MacAdam’s work using the new standard, variations in percieve color are minimalized and the MacAdam’s Elipses mapped on a 1976 CIE diagram appear much more evenly sized and circular, as opposed to oblong. This makes color comparisons using CIE 1976 significantly more meaningful.

The difference of the CIE 1976 color space, particularly in blue and green, is immediately apparent. As an example, lets look at the color gamut measurements of the iPad 2 and new iPad we used in an earlier article. Both charts do a reasonably good job of conveying the new iPad’s increased gamut coverage at all three primaries. But, the 1976 chart captures the dramatic perceptual difference in blue (from aqua to deep blue) that you actually see when looking at the displays side by side:

The increased gamut of the new iPad is worth testing. Next time you find yourself in an Apple store, grab an iPad 2, hold it alongside a new iPad, Google up a color bar image and see the difference for yourself.

So, why do we still use CIE 1931 at all?  The only real answer is that old habits die hard.  The industry has relied on CIE 1931 since its inception, and change is coming slowly.

Fortunately, CIE 1931’s grip is loosening over time. The ICDM’s new measurement standard should eventually force all remaining stragglers to switch over to the more accurate 1976 standard. Until then, you can familiarize yourself with a decent color space conversion calculator, such as the handy converter we built just for this purpose:

Is creativity the next killer mobile app?

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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.

Apple’s new iPad boasts better colors – how did they do it?

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Back to share more of our display measurement results from the new iPad. Side note before we jump in: this is a somewhat technical post, if you aren’t familiar with the general workings of an LCD, this great live teardown by Bill Hammack is worth watching: http://youtu.be/jiejNAUwcQ8

There are two ways to improve the color gamut performance of an LCD display: you can either make the backlight better or the color filters better. In both approaches, the goal is the same: to make red, green and blue light as pure as possible. The LCD display mixes these three primary colors to make all the other colors you see on screen, thus, the more pure the individual pimary colors are, the better all colors on screen are.  Based on our measurements, it looks like Apple focused on the color filters for this new display, let’s take a closer look.

In the color spectrum chart below, you can see the result of some of the color filter changes that Apple made. Notice how the red peak (on the right, in the 600 nm range) has moved to a longer wavelength. This change in wavelength means reds on the new iPad will have a deeper hue, will be less orange and more distinctly red.

Another interesting thing to look at here is the blue peak at about 450 nanometers. In our last post, we noted that blue got the biggest boost with the new display. However, the blue peak did not change in wavelength or in shape, only amplitude (or brightness), which does not affect color. So what explains the dramatic improvement in blue seen on the new display?

The above spectrum isn’t telling the whole story. It was measured from a white screen, in other words a screen with all three primary colors turned on. We see very different results when looking at a screen with a blue image, where only the blue sub pixel filters are open.

This chart shows us only the light that is allowed to pass through the blue color filters. We can see the same blue peaks that we know from the white spectrum, but there’s also some extra light getting through – notice the two small tails to the right of the blue peak? That’s green light from the backlight leaking through the blue filter.

This means that when the iPad display needs blue light to make an image, some of that green comes along with the blue whether you want it or not. You will notice that the green blip is smaller on the new iPad, meaning less green is leaking through and a purer blue is displayed.  Take a look at the comparison shot here and you can see how just a hint of that green leakage is making the iPad 2’s blue (on left) appear slightly aqua by comparison.

Blue color filter comparison: iPad 2 on left, new iPad on right

Leakage like this happens because its very difficult to make a truly perfect color filter and even harder to make one that is efficient enough for a mobile display. The reason is basic physics – a better color filter is narrower, allowing only the desired color through.  However, the narrower you make the filter, the less light it lets through, and less light through means the display has to be driven harder to maintain brightness. This directly affects battery life, partially explaining the new iPad’s need for a larger battery.  Based on our experience, we estimate that the color improvements alone in the new display probably cause it to consume about 20-30% more power than the iPad 2’s screen.

Perfecting the color performance of a display is a critical engineering challenge and worth highlighting because its one of those tiny details that Apple is so great at. Just making this small improvement in light leakage from iPad 2 to the new iPad accounts for a stunning amount of improvement in color performance and, most importantly, it makes for a richer user experience.

Apple’s new iPad display; what does 44% more color get you?

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Last Friday Apple released an updated version of one of their hottest products, called simply “the new iPad.” Central to the update is a brand new display featuring significantly more resolution and color saturation. Since the resolution bit has been covered to death by others and we’re interested in color here we thought we’d take a closer look at Apple’s color saturation claims.

Our new iPad arrived on Friday and since then we’ve submitted it to several tests using our Photo Research PR 655 Spectroradiometer.

Using the new iPad, particularly next to an “iPad 2,” the reds and greens are noticeably better, but the blues in particular are quite striking. It actually makes the blue on the iPad 2 seem more ‘aqua’ than pure blue. The color data bears this out.  According to our measurements, Apple has significantly increased the saturation in all three primaries, most notably in blue:

The key color claim that Apple made on stage at the iPad announcement was that the new iPad has 44% more color saturation.  What they mean by that of course depends on the context.  There are a couple of different color measurement standards that Apple could be gauging the performance of the new iPad against such as CIE 1931 or CIE 1976.

An easy way to think about these standards is a bit like the temperature measures that we are all familiar with, Celsius and Fahrenheit, in that they are different ways communicating the same information. Saying, “it’s 5 degrees warmer today” means something very different to users of each system and its much the same way with color spaces, only we’re talking about measuring how the eye perceives color, not how warm it is outside.

We should also note that when people in the display industry talk about color saturation as a percentage, it is common practice to refer to a color gamut standard within a CIE color space. There are many color gamut standards in use today including: NTSC, sRGB, Adobe RGB 1998, DCI-P3, and rec 709. Each of these standards is a subset of a CIE color space. They are typically used by content creators to ensure the compatibility of their work from device to device. For example, if I create an image in Adobe RGB, I would like to display it on a screen that can show all of the colors in Adobe RGB in order to make sure it accurately reproduces all the colors in my original shot.

Based on our measurements it looks like Apple is referring to the NTSC gamut within a color space. But which color space do they mean?

A 44% improvement within the CIE 1931 color space would give the new iPad the equivalent of the sRGB standard used by HDTV broadcasts, Blu-Ray and much of the web. Given the significance of achieving that standard, some thought Apple must have been trying to say “sRGB” without confusing consumers by describing the meaning of various color standards.

According to our data, this is not the case. The new iPad only manages about 26% more saturation over the iPad 2 when measured against the CIE 1931 NTSC color space. However, the unit we measured showed a 48% increase in saturation when measured in the CIE 1976 color space, so that must be Apples frame of reference.

Measurements and standards aside, the new display looks great. The improvement in color performance will greatly enhance the user experience, and as we discussed yesterday, show’s what Apple is betting on for the functionality of future devices.

In our next post we will explain exactly how Apple achieved this improved color performance and look at ways they can improve the next generation.