Quoted from CNET (regarding iPhone 4's screen):
- Improvements, especially resolution, tend to have diminishing returns--it's really tough to see the difference between same-sized 1080p and 720p TVs with moving video, for example. The way a manufacturer implements the technology, for aspects like color reproduction, reflectivity, and gamma, can have a larger impact on image quality than any published specs. Finally, the content, the viewing environment, and even your own visual acuity all affect how an image will look to you on the new iPhone 4's screen.
- 960x640 resolution: This is the native resolution of the Retina display, which crams 614,400 pixels onto a 3.5-inch diagonal screen (326 pixels per inch). That's four times as many pixels as the current iPhone, which has a 320x480 native resolution on the same-sized screen (163 PPI), and significantly more than newer competitors like the Motorola Droid (854x480, 265 PPI) and the Nexus One (800x480, 252 PPI), for example. As Jobs pointed out, 300 PPI is typically regarded as the limit of useful pixel density, and the iPhone 4's mark of 326 is among the best available on any display.
- Text, especially smaller fonts, should appear sharper and less pixelated when you look closely in a side-by-side comparison between the old and new iPhones. The difference with photos will be a lot more subtle, on the other hand, while the difference with moving video might not be visible at all. It's simply easier to see differences in resolution with black-and-white, line-based material, especially when it's not moving. In any case, you'll have to look closely to see them. Compared with other screens with higher pixel densities than the current iPhone, the differences in detail will be even smaller.
- We say "should" because material that's not designed for the higher resolution--Jobs said the new iPhone iOS 4 would be, and encouraged App designers to update to higher rez--has to be scaled to fit the pixels. It's the same as watching a DVD (720x480) on a typical high-definition TV (1920x1080); it will look good, but since it's not a high-resolution source to begin with, the extra pixels are basically wasted. A typical YouTube video on the new iPhone 4, for example, won't benefit from the extra pixels. Icons and photos in the browser, on the other hand, might indeed look slightly better if Apple does the scaling correctly.
- The analogy between an HDTV and an iPhone 4 can be misleading, however, because the distance between your eyes and the screen is so different. Holding the iPhone six inches from your face, you'll be able to appreciate differences that simply aren't visible on a screen 10 feet away. The closer you hold the screen, the more apparent the improved pixel density will be. And larger images--like, say, the massive iPhone 4 projections Jobs used to illustrate the Retinal display during his speech--show off the differences better as well.
- IPS technology: Speaking of OLED, Jobs called the IPS-based (in-plane switching) LCD screen used by Apple "quite a bit better than OLED." That remains to be seen, but in general, OLED will produce higher contrast, by virtue of its ability to display a darker black, stay truer from off-angle, and draw less power with the screen turned down. Conversely, LCD (and IPS) will be more efficient at high brightness and not wash out as much in high-ambient-light situations. Both technologies, when implemented well, can look great on phones, but in our view IPS is certainly not better by default than OLED or AMOLED. The same goes for the LED backlight and ambient light sensor Apple uses--their main benefits are realized in increased efficiency.