Smartphone Displays - AMOLED vs LCD
DisplayMate’s thorough testing debunks some myths, related to OLEDs and LCDs, which might be valid in the lab, but in real production units, the results are as follows, regarding the Super AMOLED display on the Samsung Galaxy S, and the IPS-LCD Retina Display in the iPhone 4.
The color depth on the iPhone 4 appears true 24-bit (i.e. capable of 16 million colors), while due to Android 2.1's limitations, the browser and gallery in the Galaxy S are reproducing 16-bit (65536) colors. This is fixed in Froyo.
The 4” Super AMOLED screen has enough resolution at 480x800 pixels, but the picture appears less sharp, especially when reading text, because the PenTile OLEDs have only 2 sub-pixels per pixel, instead of the 3 that are used in most displays. The Super AMOLED exhibits a blueish tint when showing white, which is a factory calibration issue, and there are projects under way to boost the screen brightness and dispose of the blueish whites, such as the Voodoo project. In our sample shots inside at maximum brightness in the browser, our main page indeed looks pixelated on the Super AMOLED:
Now off to the other intriguing findings. The actual brightness of the Retina Display is much larger than most screens, the excellent 541 cd/m2. This is quite a bit more than the Galaxy S’s peak 365 cd/m2, and a very important advantage, since phone screens are usually used in a lot of ambient lighting. That brightness unfortunately degrades with 57% from a 30 degrees viewing angle on the iPhone 4, and there isn’t much that can be done about it, apart from switching to AMOLED technology. The special reflectance coating brings brightness degradation to the Samsung's phone as well, which is unusual for an AMOLED screen, but not as bad as to the IPS-LCD, as our inside samples show:
On another note, the contrast ratio on the Samsung Galaxy S is so high, that DisplayMate has marked it as "outstanding - greater than 61000:1", while the iPhone 4’s is marked as the “very good for mobile” 1117:1. Contrast ratios only matter when the ambient lighting is low, though, rarely the case with your cell phone, as the source rightfully notes.
One component where Super AMOLED excels, and is extremely important in bright sunlight, is the reflectance percentage. Samsung is advertising 4% reflectance, with the actual measured 4.4%, but this is still extremely low, and less than the iPhone’s 7%, which makes up for the brighter Retina Display, especially in broad daylight. That is why outside both screens are almost equally visible, whereas AMOLEDs previously held issues against LCDs in that respect.
Still, all screens perform pretty bad in direct sunlight, and the technologies should be constantly evolving to address that. Our own sample shots of the two screens outside at maximum brightness confirm the above mentioned observations:
The color gamut is another important eye candy – the Galaxy S produces vivid, oversaturated colors, which people immediately like, representing 138% of the gamut, whereas the iPhone 4’s colors appear washed out in comparison due to it representing only 64% of the color gamut. If you are a calibration specialist, the Super AMOLED’s colors are called gaudy, and limited color gamut preferred over the much larger one. If you are a regular user, though, the colors on the Super AMOLED will wow you, the same way oversaturated photos of the iPhone 4 can wow you over the undersaturated colors of the Nokia N8 at first. We think Samsung deliberately has let the colors stay “gaudy”, and we can’t blame them.
Without some clarity, color or contrast, one can manage, but if your screen is a power drain, you will quickly move on to a better smartphone. Battery life when talking over 3G and watching video on both handsets is comparable, over similar capacity batteries and chipsets. The reason the Super AMOLED doesn’t fare way better, as the lack of backlighting would indicate, is the improved power management of the IPS-LCD on the iPhone 4, and the above mentioned power-drain when AMOLED screens are displaying white.
We’d think that these issues are not as important as in the first OLED screens, but the actual measurements prove us wrong. With an entirely white screen at full brightness, the Galaxy S consumes 1.13 watts, and the iPhone 0.42 watts. When showing mixed colors with darker content, the consumption of both is around 0.2 watts, and at entirely black screen the Galaxy S consumes zero, while the iPhone 4 stays at 0.42 watts. No wonder the backgrounds of the menus in the Galaxy S and the Samsung Wave are black.
Therefore, to draw the line in the sand in the Super AMOLED vs IPS-LCD battle, we have to note that both are outstanding representatives of two technologies – one very mature and one fledgling. If you had to choose only by screen type, here is how the odds are stacked. Provided that you read a lot of e-books, browse the general internet (which consists mostly of pages with white background), or review a lot of office documents on your smartphone – you will probably go with IPS-LCD, capable of the amazing resolution of the Retina Display, which makes text crisp and legible.
If you are using your smartphone heavily for viewing photos and video, you can’t find anything better than the high-contrast Super AMOLED, due to the bright, oversaturated colors, which many people like. Below is a sample clip we made that plays the same YouTube clip on all handsets for comparison, and it is clear that the Super AMOLED has the upper hand when displaying video:
Display technologies are not like advances in chipset miniaturizations, where GHz increase and power consumption have been moving in inverse relationship according to Moore’s law for the last fifty years or so. Screen production methods are taking years to be perfected, tested, calibrated, and ready for mass market adoption. Thus, the current overview might be valid for your smartphone purchase for a few more years, unlike our mobile CPU article, which we will have to update, mere two months after publication. Let’s have a look at some of the wild things that are expected from the screens of the future, and judge for ourselves where technologies are heading.