Picture quality is mostly very commendable. The fast innate response time of plasma technology ensures that 3D images suffer much less from crosstalk noise than any sort of LCD screen and makes images immediately appear sharper, more natural and less tiring to watch for prolonged periods.
Even more impressive, though, is the brightness and colour response. With the Monsters Vs Aliens Blu-ray, for instance, the picture is a notch or two brighter and richer than on Panasonic's plasmas, even approaching the degree of dynamism usually only seen on LED displays.
Avatar in 3D looks even better; it becomes apparent with true video content – as opposed to animation – that the colours during 3D are outstandingly natural. In fact, they're arguably more natural than the set's 2D palette.
The dimming effect of the glasses effectively filters out a minor black level shortcoming in the panel to be discussed shortly, reinforcing the sense that to some extent the 50PX990's 3D pictures are ultimately more impressive than its two-dimensional ones.
The only negative thing to say about the 50PX990's 3D pictures is that while they aren't bothered by crosstalk nearly as much as those of LCD TVs, there is definitely more of it than you get with Panasonic's 3D TVs. This is particularly apparent when playing Black Ops and is messy enough to warrant a swift return to 2D mode.
Given that crosstalk remains the single biggest distraction when watching 3D, that leaves Panasonic's 3D TVs as the best 3D screens around – despite their lower 3D brightness – with the LG sneaking into second place. Though of course, Panasonic's equivalent 3D model is considerably more expensive than the 50PX990.
The 2D to 3D conversion circuitry is reasonably convincing, but sometimes suffers from distracting depth miscalculations and generally feels rather gimmicky.
Black levels during 2D playback are pleasantly deep and convincing by general flat TV standards, though are neither as pitch black nor as full of shadow detail as the very best plasma or direct LED TVs.
Colour tones (usually when watching relatively low-quality standard-definition sources) can sometimes look slightly off key and a lack of tonal subtlety occasionally gives flesh a somewhat waxy quality.
However, these issues diminish considerably when watching high-definition material, and can be improved via a little time in the colour management menus. Given how good colours look in 3D mode, though, it still feels at times as though the TV's core colour settings were established with at least one eye on 3D playback.
High-definition pictures are extremely clean and detailed, while its standard-definition pictures avoid the overt noisy, soft look sometimes seen with previous LG TVs. The general sense of sharpness is done no harm at all, of course, by the plasma panel's fast response time ensuring that images are almost entirely free of the sort of motion blurring that plagues LCD TVs. There's a bit of judder at times, but this is one area where the 50PX990 outguns Panasonic's screens, at least with 50Hz material.
The 50PX990 can also be watched from a very wide angle without any loss of colour saturation or black level response, unlike most liquid crystal sets.
The last points to be raised in this section are, unfortunately, negative. 'Trigger twitch' games, such as Call of Duty, seem to display more input lag than is ideal, particularly if you forget to switch the set to its 'Game' picture preset.
Next, in keeping with other recent LG plasma TVs, there's a bit too much image retention around for comfort; you can clearly see shadows of parts of earlier images hanging over current images for a few seconds.
This only tends to persist for a few minutes after turning the TV on from cold and its residual impact should diminish over time, but with rival plasma sets from Samsung and Panasonic scarcely suffering from this problem, it is annoying to have to tolerate it to even a small degree.