A closer look at the display
The display is one of the most important parts of any computing device—tablet, convertible, or otherwise. You really can't avoid looking at the thing. On the VivoTab RT, Asus is using the TrueVivid screen technology that first appeared in the Nexus 7 tablet it manufactures for Google. The key here is consolidation. Touchscreens typically stack multiple individual layers on top of the LCD panel. The VivoTab RT combines those layers, reducing both the weight and thickness of the screen.
The VivoTab's touch sensors are attached directly to the screen's top layer of scratch-resistant Corning Fit glass. That piece is then bonded to the LCD panel using a clear adhesive, eliminating the air gap that typically sits between the glass and the LCD. The end result is a single component measuring just one millimeter thick, more than 50% thinner than designs that rely on separate layers. This bonded screen purportedly allows more light to pass through it, as well. Asus claims the screen's transparency is 94%, compared to as little as 82% with lesser designs.
In addition to letting more photons pass through the screen, the VivoTab RT fires more of 'em at the display. The screen is a SuperIPS+ type, which means it has a turbo-charged backlight designed to improve readability in outdoor light. Asus says the backlight delivers a maximum of 600 cd/m²—that's candelas per square meter, the standard measure of luminance otherwise known as a nit. Our colorimeter registered only 525 nits with the VivoTab's screen cranked all the way up, but that's still much higher than typical tablet and notebook displays.
The screen is easily bright enough for indoor use, and it fares pretty well outdoors, at least under the overcast skies that will blanket the Pacific Northwest for the next six months or so. I'll let you know about visibility in direct sunlight some time in April or May. Having used a couple of different SuperIPS+ tablets over the summer, I can say that extra backlight brightness makes glossy tablet displays much easier to read on a sunny day. Reflections still persist, and the picture is far from perfect, but brighter backlighting is a definite improvement.
Brightness isn't the only measure of display goodness, of course. PPI, or pixels per diagonal inch, has quickly become one of the most quoted metrics used when describing a screen. The VivoTab has a 10.1" panel with a 1366x768 display resolution, which works out to a relatively pedestrian 155 PPI. That pixel density is quite a bit lower than the 224 PPI of the Transformer Pad Infinity, which offers a 1920x1200 display resolution on panel of the same size. The iPad 3's Retina panel delivers an even higher 264 PPI.
Obviously, higher pixel densities are better. Having more dots on the display enables sharper images and crisper text. How those pixels are used is important, though. Windows RT features a ClearType HD subpixel font rendering scheme that makes text on the VivoTab look surprisingly good when the tablet is held at arm's reach. Let's take a closer look to see what's going on.
The images below show browser output on the VivoTab RT, the Transformer Pad Infinity, and the original Transformer (which has a 10.1", 1280x800 display with 149 PPI). Each tablet was configured in portrait mode, with Internet Explorer on the VivoTab and Chrome on the Transformers 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 surfaces of the screens, and all the images were cropped and resized in the same way. Click on the buttons below the images to see the results for the various tablets.
The fact that Internet Explorer uses a different font than Chrome makes our comparison less than perfect, but the differences are easy to see. The VivoTab RT's pixels are about the same size as the ones on the old Transformer. However, the VivoTab's text has more shading around the edges of each letter. This subpixel antialiasing creates a slightly blurred effect that does an admirable job of cutting down on the number of visible jagged edges compared to the Transformer's output, which looks blockier to my eyes.
If you bring up the images for the Transformer Pad Infinity, it's evident that ClearType isn't enough to make up for the VivoTab RT's low display density. The Infinity's text output looks much cleaner up close and from afar. Just as hot rod aficionados maintain that there is no replacement for displacement, it's clear there's no substitution for resolution.
We don't have a picture of this particular portion of text rendered on the iPad 3, but that tablet has even better text quality than the Transformer Pad Infinity. You can see how the two compare on this page of our Infinity review.
Now that we've seen the size of the pixels, let's talk about the size of the screen. The VivoTab RT's display has the same 10.1" diagonal measurement as the Transformer Pad Infinity. However, the VivoTab's 16:9 aspect ratio is less square than the Infinity's 16:10. The resulting difference in total screen area amounts to a couple square inches: 43.6 on the VivoTab versus 45.8 on the Infinity. The iPad 3's 9.7", 4:3 panel has a total area of 45.2 square inches. The Microsoft Surface RT's screen is even larger, with the same 16:9 aspect ratio and resolution as the VivoTab RT on a 10.6" display with a total area of 48 square inches.
Next, we'll consider the VivoTab RT's color reproduction using our colorimeter. We tested the display using the same ~120 cd/m² brightness setting as a number of other tablets, including the iPad 3, the Transformer Pad Infinity, and the Transformer Pad 300 (whose 1280x800 display is similar to that of the old Transformer). We'll start by looking at the display's color gamut, which you can compare to the other tablets by clicking the buttons below the image.
The triangle outlined in white represents the range of colors covered by the panel. As the gamut plot makes clear, the VivoTab RT is working with a more limited palette than the iPad 3. The panel's color gamut is more comparable to Asus' other tablets, which have similar skewing toward blue and purple tones.
If a screen's output is too biased, colors can look a little off, and whites can exhibit a tinge of something else. We can get a sense of the display's color bias by plotting its color temperature, which we've done below. Again, click the buttons to bring up the plots for each tablet.
Ideally, a display's color temperature should be 6500K, which matches natural daylight. The VivoTab RT produces cooler tones overall, particularly as the gray level ramps up. All of the other tablets come much close to the 6500K ideal.
The screen's cooler color temperature makes whites look slightly bluish, an artifact I didn't really notice when using the VivoTab on its own. There's also a lot of blue in Windows RT's touch-friendly UI and even in the traditional desktop environment, which probably helps the cooler color temperature blend in.
That said, the cooler tint is readily apparent when the VivoTab is viewed side-by-side with the Transformer Pad Infinity, which has a more neutral color temperature. When you look at the two screens next to each other, there's no denying which one is superior. The VivoTab RT's screen is good, with vibrant colors and clear text. However, the Infinity's display imparts a sharpness to both images and text, and the difference is easily detectable at normal viewing distances.
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