Tag Archives: color performance

ITU agrees on HEVC h.265 codec

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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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Gizmodo: Tech’s New Most Meaningless Spec: PPI

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source: Gizmodo

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

Adrian gets to the heart of the problem:

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

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

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

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

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

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

Measuring Up

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

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

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

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

How did they do it?

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

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

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

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

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

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

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

Conclusion

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