Dr. Raymond Soneira of DisplayMate Technologies has made it his mission to suss out the best smartphone, tablet, HDTV, and multimedia displays from the worst with his Display Technology Shoot-Out series. Here, he dissects the screen on Google’s Nexus 7.
Editor’s note: Dr Soneiera confirms the problem with the Nexus 7 we raised in our review, but I’ve written a quick follow-up piece to this one saying that it doesn’t matter one bit how rubbish the display is on the new 7-inch tablet.
The Google Nexus 7 is the first of the second generation 7-inch tablets out of the gate. and it sure looks like it could be a winner. The published display specs look pretty good, and some of the basic Lab measurements also look pretty good. But just like in Triple Crown races, an important but overlooked issue can spoil the outcome. In this Display News item we’ll explain what went wrong with the Nexus 7 display — the details will appear in our upcoming in-depth 7-inch Tablet Display Shoot-Out.
The display on the Nexus 7 sounds great on paper — a 1280×800 display with 216 pixels per inch (PPI), within the PPI sweet spot we have recommended for Tablets, so text and graphics appear very sharp, but not as sharp as on the new iPad 3. It also has a premium IPS LCD, the same technology found on the iPads and the first generation Kindle Fire, which provides excellent wide viewing angles. In the lab we measured the Nexus 7’s brightness (luminance) to be about 350 nits, comparable to most other 7-inch LCD Tablets. Its display contrast ratio is about 1,000 which is excellent for mobile displays. So far so good.
Next we measured the colour Gamut, something where almost all mobile LCDs come up short in order to improve power efficiency and battery running time. They typically provide only about 60 per cent of the ideal standard colour gamut, which results in somewhat subdued colours in all displayed images, including photos and videos. For the Google Nexus 7, we measured an impressive 86 per cent of the standard gamut — not as good as the new iPad 3’s 99 per cent, but much better than most existing LCD tablets and smartphones. So far, it sounds really good — but let’s see how good it actually looks.
Even before I examined the display with our DisplayMate diagnostic test patterns I knew something was seriously wrong when I looked at the first of many sets of standard photos that we use to visually evaluate displays. Normally we compare everything to a calibrated professional studio monitor to check for image and colour accuracy. But that wasn’t necessary with the Nexus 7 because many of the images were noticeably washed out — they looked like over exposed photographs with missing highlights, reduced image contrast, and weak colours. However, darker images look a lot better than brighter ones, which actually tells us a lot about its cause.
So, what’s the problem? The Intensity Scale (often called the grey scale) is way off. The display’s brightness fails to increase sufficiently for bright image content, causing bright image detail to be compressed and lost. See the figure at left for the Nexus 7 and this figure to see what the Intensity Scale should look like. The Nexus 7 Display stumbles and falls short both figuratively and literally.
There is about a 25 per cent compression of bright image content, which is quite substantial. This holds for both the Gallery Viewer and the Chrome Browser. On some cheap displays this is done intentionally by the manufacturer because the compression actually makes them appear artificially bright. Here I think it’s probably just incompetence by the manufacturer, which is too bad because they messed up a really nice display. Depending on the display firmware this may or may not be correctable with a software update. These tests were made under Android 4.1.1.
The Nexus 7 has a high quality display, they just really messed up the factory calibration. This affects all displayed images, but it is most noticeable on any form of photographic image, including videos, because the colour and intensity mixtures are visually critical for them to look right. The analogy of an over exposed photo is a good one. For high contrast software generated text and graphics the display will look fine.
In short, the display produces washed out images and colours in spite of the fact that it has a display with excellent colour saturation and contrast.
Looks like Google didn’t pay enough attention to the Steve Jobs memo that the key to a successful Tablet is an outstanding display. If high image and picture quality is important to you, then you might want to skip the Google Nexus 7 and wait for a Tablet with a better display, or wait and see if Google can correct the problem.