Display Quality: Color Gamut
We've seen doubters out there skeptical of whether the TouchPad actually employs an IPS screen. Based on our observations under the microscope, we can confirm that this is an S-IPS panel. In fact, based on the subpixel structure, HP appears to be using glass from Samsung.
Even though mobile operating systems don't honor ICC color profiles, native color management does occur at the hardware level. When a GPU sends 10 different hues of blue to an LCD only capable of displaying three, the subpixels display the closest matching color. So, in a way, smartphones and tablets behave as if they’re using relative colorimetric rendering. For more information, read Tom's Hardware Benchmarks Inkjet Printer Paper!
In terms of color quality, the TouchPad delivers the most color that we've seen from any tablet. Even though it uses a panel similar to the iPads, HP achieves a higher gamut volume by using a default calibration closer to the AdobeRGB 1998 spec.
We have to make a couple of adjustments in order to generate these gamut measurements. First, we disable dynamic brightness because it doesn’t facilitate an accurate (or reproducible) measurement of the display’s potential. Second, brightness is set to the highest value. If you don't use the same settings, your color gamut is going to look smaller than what we're showing here.
Compared to the S-IPS panels on the iPads, HP achieves a slightly lower contrast ratio due to stunted white luminance. The color temperature is exactly at 6500 K, resulting in accurate color representation, but the low gamma distorts color perception. Gamma doesn't affect black or white performance, but it does affect midtones. If gamma is set too high, they appear too dark. If it's set too low, midtones appear too pale.
Adobe, Apple, and Microsoft all recommend a gamma of 2.2. It's an arbitrary value carried over from the NTSC standard, but it was originally chosen because it allows colors to appear more natural in slightly dim environments. The TouchPad's slightly lower gamma value suggests that it's best used in a darker environment. This is really the only weak point of the TouchPad's display. In every other attribute, HP seems to be hitting the AdobeRGB 1998 reference spec.
