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09
Jul
2014

LG launches first QHD smartphone – has it done enough?

POSTED BY Steffen Sorrell
“Jobs, you need a new pair of spectacles, mate”: a statement I imagine to have passed through designers’ minds at LG following the launch of its latest flagship smartphone, the G3.  It seems not so long ago that the iPhone 4 was launched, along with claims from the late Steve Jobs that around 300 PPI (Pixels Per Inch) would deliver a display full of indiscernible pixels if viewed at around 10-12” from the eye. This claim has since been debunked given the fact that the human eye is capable of resolving an enormous amount of detail, in particular with regards to the alignment of two separate line segments, a hyper-acuity phenomenon known as Vernier acuity.

Although OEMs have a preference for touting their displays in terms of PPI, similarly to the Megapixel race of the DSLR era, this number is meaningless unless one considers other variables. In the case of mobile device displays, the dominant variable to consider when assessing the perceived quality of a display in terms of resolution is the viewing distance. For example, the further the eye is from the display, the fewer PPI that are required in order to make the image appear sharp. A better measurement in this case is to consider the PPD (Pixels per Degree) value, which accounts for viewing distance as well as pixel density, ie the number of pixels per degree of viewing angle; 300 PPI equates to around 60 PPD assuming a viewing distance of 10”.

While the eye is theoretically capable of discerning individual pixels in the region of 120-150 PPD in general cases, the G3’s display equates to some 93 PPD at 10” viewing distance; however, as screens move beyond the so-called Retina resolution of 60 PPD, the law of diminishing returns comes into effect. A parallel here can be drawn with the increase of TV resolutions from SD (Standard Definition) to 720p to 1080p; SD to 720p was seen as a giant leap, while the effects of moving from 720p to 1080p were not as noticeable. In a nutshell, the greater the resolution of the display, the smaller the proportion of the population that is able to appreciate the differences. At the same time, as the pixels are more densely packed together, the harder the backlight has to work in order to achieve the same luminance as a display with a lesser pixel density. LG, in its efforts to maintain battery life parity with previous generation devices, has therefore had to compromise on a number of aspects, one of which is to lower the display’s maximum contrast.

Those in the photography world know that in both analogue and digital imaging, a manner by which perceived sharpness can be increased is by using a so-called “unsharp mask” to effectively increase edge contrast; indeed, contrast ratio is one of the defining variables in dictating image sharpness. The LG G2 is known for its excellent battery life while sporting a 1080p display with a notably higher contrast ratio in comparison to the G3; one has to question therefore, whether LG has made a mistake with the QHD differentiation given the compromises made with illumination of the display. With battery life increasingly becoming a limiting factor where taking full advantage of smartphone features are concerned, a smarter move would surely have been to further improve on the G2: better battery life encourages use of the device, which in turn drives the revenue ecosystem and higher brand loyalty. While QHD does indeed approach the “perfect” resolution for smartphone screen sizes, it appears as if the overall technology is not quite there yet.