Lots of pixels on a smaller screen
After unpacking the Nexus 7, I was excited to see that the screen's bezel is much narrower on the left and right edges when the tablet is held in portrait mode. Typical tablet bezels measure around 20 mm wide, but the Nexus' screen is framed by only 10 mm of bezel on two sides. Smaller bezels are better, right?
On a monitor, sure, but not necessarily on a handheld device. When I hold a tablet in one hand, my thumb naturally rests on the bezel. 20-mm bezels have plenty of room for the thumbs on my XL-sized hands, but the Nexus 7's narrower frame does not. Unless I'm careful, my thumb invariably activates the touchscreen, generating unwanted clicks and sometimes messing with gestures I'm performing with the other hand. I'm learning to hold the device with my thumb in a more vertical position, which seems to stave off inadvertent screen contact. Because the Nexus 7 is so small, it can also be cradled in one hand, with the edges securely pinched between one's thumb and fingertips and no contact with the bezel at all.
The Corning glass panel that stretches across the screen and the surrounding bezel is highly reflective, but the LCD's backlight has more than enough punch to overpower reflections in normal indoor lighting. The picture above was taken with the brightness set at just 25%, which is where it stayed for most of our testing.
While the lower brightness level is sufficient for indoor use, you'll need to crank the slider all the way up to do any reading in direct sunlight. Even then, anything other than dark text on a light background is difficult to make out.
According to our colorimeter, the screen has a maximum luminosity of 298 cd/m², putting the Nexus 7 at the low end of the tablets we've tested. That's not a surprise given the price tag, and it certainly doesn't impede the tablet's readability when the backlight isn't forced to compete with the hail of photons raining down from the sun.
Another factor that affects the display's readability is its pixel density and overall size. 1280x800 pixels packed into a 7" panel works out to 216 PPI, or pixels per inch. That's much higher than the 149 PPI offered by the same resolution on a 10" panel and pretty close to the 224 PPI delivered by the 10", 1920x1200 Transformer Pad Infinity.
Let's see how the on-screen text looks up close. The pictures below are of the Chrome browser's output on three tablets: the Nexus 7, the original Transformer (which has 10", 1280x800 display), and the Transformer Pad Infinity. Each tablet was configured in portrait mode, with the browsers zoomed in to show only the main text column from Scott's article on Nvidia's "Big Kepler" GPU. The camera lens was placed exactly 5" from the surface of the screens, and all the images were cropped and resized in the same way. That should give us a sense of the relative differences in text and pixel size.
The Nexus 7's pixels look almost as small as those of the Infinity. They're tiny compared to the old Transformer and pretty much invisible to the naked eye when holding the tablet at a reasonable distance. Thanks to its higher PPI, the Nexus 7's text is much clearer than the old Transformer's, with fewer jagged edges. The Infinity's text output is crisper still, but the iPad 3's 264-PPI Retina panel tops them all.
There's also the matter of size. As you can see, the Nexus 7's text is substantially smaller. Remember that we're browsing a desktop site with the main text column filling the screen on all three tablets. Sites optimized for mobile devices should default to a larger font, and some folks might find surfing mobile sites on the Nexus more comfortable as a result. My less-than-perfect eyes can still make out the text on desktop versions of the handful of sites I read regularly, so I haven't resorted to browsing their mobile variants. Text size is less of an issue with apps like Gmail and the Kindle e-reader, which feature adjustable font sizes.
Our final step in display analysis probes the screen's color reproduction using our colorimeter. Below are the color gamut graphs for the Nexus 7 and a handful of other recent tablets at a screen brightness of ~120 cd/m². Click the buttons under the graph to load up the one associated with each tablet. You might have to wait a second or two for a new image to load after each click.
The Nexus 7's IPS panel covers a decent swath of the spectrum. It's definitely biased toward blue and red tones and a little short on shades of green and yellow. Neither the Nexus 7 nor the Transformers comes close to matching the glorious color reproduction of the iPad 3's Retina panel.
We can also use our colorimeter to measure color temperature. Here, we're looking for a value close to 6500K, which is the temperature of typical daylight. Again, clicking on the buttons below the graph will load up the plot for each tablet.
Although the Nexus 7 rarely hits the 6500K mark exactly, it comes closer to the ideal over a much broader range of gray levels than the high-PPI Transformer Pad Infinity and iPad 3. The Transformer Pad 300 produces slightly better results than the Nexus 7 at all but the 10% gray level. To my eyes, the Google tablet's whites look neutral, with no apparent hint of other tones.
Some of that whiteness invades the colors, which look a tad washed out versus the Transformer Pad Infinity. I flipped through a collection of particularly colorful images on both tablets side by side, and the difference was hard to miss. On the Nexus 7, blue skies looked slightly hazier, my dog's copper coat appeared a bit sun-bleached, and green foliage lacked a smidgen of lushness. It was as if a little life had been sucked from the rainbow.
The Tegra 3 SoC may be responsible for the paler tones. The Nexus 7 takes advantage of the chip's Pixel Rendering Intensity and Saturation Management (PRISM) scheme, which is supposed to conserve battery life by dimming the backlight and "enhancing" the colors to compensate. Some richness may be lost in the translation.
Don't get me wrong; the Nexus 7's display still looks good overall, and it's a heckuva lot better than the cheap TN panels we've seen in all too many netbooks in the same price range. The 7" display has wide viewing angles, too. Just don't expect its output to be quite as vivid as the best examples on the market. Naturally, those displays are reserved for high-end tablets that cost a lot more than the Nexus.
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