Screen comparison: G3 vs Xperia Z2 vs Galaxy S5 vs One (M8) vs iPhone 5s
Ah, color reproduction – such a complex area to explore, but also one that's extremely important, as it determines how good-looking and accurate a screen is going to be to a large extent. There are a lot of metrics here to look at, so let's get going!
Color temperature is one of the most important things to consider. It represents the balance between red and blue in the display, and determines if your screen is going to have a colder or a warmer tone to it. Color temperature is measured in Kelvin, and the reference value is 6500. It's typical for smartphones to usually exhibit a slightly colder/bluish look, and neither of the participants in this comparison are exception to the rule. The Xperia Z2 does best here with a color temp of 6900 K, which is quite good. The iPhone 5s and HTC One (M8) follow closely behind with 7150 K, slightly edging the G3's 7300 K. The Galaxy S5 is worst in this respect. In Standard screen mode, it hovers around the 8100 K mark, although you can switch to Professional or Cinema mode in order to bring this down. Still, even though the GS5's temperature can get relatively close to the reference value, it suffers from another problem — too much green color — which prevents it from looking... well, good. Such kind of excessive green isn't present with the rest of the gang.
Gamma is also an important metric, as it will indicate if the phone would assign the correct brightness level to various items in the content. The reference is 2.2, but some manufacturers opt for a higher gamma as it typically suggests more contrasty visuals. In this category, the iPhone 5s is king, with its average gamma of 2.21. The Galaxy S5 isn't far behind with 2.25, while the Z2 is remarkably off with 2.59. The G3 has a gamma of 2.32 – pretty decent, though just a bit more contrasty than needed. Finally, the One (M8) has a slightly low gamma of 2.11, suggesting that certain areas will be a bit brighter than necessary.
Delta E is a metric used to indicate the average color inaccuracy of a display. We measure it in two different ways: once by using a greyscale, and once by measuring primary and secondary colors. In addition, by analyzing the CIE charts containing the measurements of the screens, we can see just where the faults happen to be. In this department, it is the iPhone 5s that gets closest to the reference values with its Delta E greyscale of 2.66 and Delta E color (or rgbcmy) of 3.36. Bear in mind that values of up to 3 are considered in the 'great zone'; values between 3 and 5 are OK, but going over 5 means that there are significant color inaccuracies exhibited by the display in questions. But back to our ranking – the G3 actually follows pretty closely with Delta E greyscale of 3.82 and Delta E rgbcmy of 3.78. All the other phones stay in the safe zone of up to 5, with the exception of the Galaxy S5, which has a Delta E greyscale of 5.08 and Delta E rgbcmy of 7.38, which is rather high. That is if we examine the phone's Standard display mode. We won't go into detail about the characteristics of the rest of its screen modes, because none of them manages to push it into the 'acceptably accurate' domain. Still, if you're interested about those other screen modes – you can find that info here.
If we take a closer look at the CIE charts, we can then see that in what way each of the handsets deviates from the standard. The Sony Xperia Z2, for example, stick with an evenly spaced gradation of colors, but tends to oversaturate each and every shade to a small extent. On the other hand, the HTC One (M8) prefers to stay closer to the confines of the sRGB colorspace, but boosts certain midrange shades in order to achieve a more intensive color effect. The LG G3 has a similar approach, but the oversaturation effect is a bit more exaggerated with it, compared to the One (M8). Meanwhile, if we take a look at the Apple iPhone 5s' chart, we can see how much closer it is to the reference values (the dots are very close to their respective squares). This indicates that there isn't any cheesy oversaturation going on.
Beyond the various aspects that we examined, we, naturally, find that the Galaxy S5 differs from the rest by offering fancy, yet overly-inaccurate colors. They do appear very eye-catching at first glance, but we have to take into account how far from target they are, often resulting in certain things looking a bit weird on screen.