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

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.

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

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?

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.

John Gruber on new iPad design compromises

Apple made the display a priority with its latest iPad release, breaking an unwritten rule that their products should get thinner and lighter with each release, not the other way around. John Gruber of daringfireball.net hit the nail on the head in his review of the new iPad:

Which brings us to an immovable object meeting an irresistible force. Apple doesn’t make new devices which get worse battery life than the version they’re replacing, but they also don’t make new devices that are thicker and heavier. LTE networking — and, I strongly suspect, the retina display3 — consume more power than do the 3G networking and non-retina display of the iPad 2. A three-way tug-of-war: 4G/LTE networking, battery life, thinness/weight. Something had to give. Thinness and weight lost: the iPad 3 gets 4G/LTE, battery life remains unchanged, and to achieve both of these Apple included a physically bigger battery, which in turn results in a new iPad that is slightly thicker (0.6 mm) and heavier (roughly 0.1 pound/50 grams, depending on the model).

50 grams and six-tenths of a millimeter are minor compromises, but compromises they are, and they betray Apple’s priorities: better to make the iPad slightly thicker and heavier than have battery life suffer slightly.

This point can’t be understated. For Apple, the quality of the display, both in terms of resolution and color gamut, is so critical to the experience of using an iPad that they were willing to make some major tradeoffs. In this case they not only ended up with a slightly thicker, heavier device, they also used a significantly more expensive part. The end result is a stunning display that amplifies everything that was already great about the iPad 2 so it looks like a tradeoff worth making.

We took some color performance measurements of our new iPad this morning and we’ll be posting more details shortly.