Don't believe the hyperbole - the iPhone 4 does not have a resolution higher than the retina.
This is according to Dr. Raymond Soneira runs DisplayMate Technologies, who claims that Steve Jobs is flat out wrong in saying that the screen on the iPhone 4 has a higher resolution than the human retina:
Steve Jobs claimed that the iPhone 4 has a resolution higher than the retina - that's not right:
1. The resolution of the retina is in angular measure - it's 50 Cycles Per Degree. A cycle is a line pair, which is two pixels, so the angular resolution of the eye is 0.6 arc minutes per pixel.
2. So if you hold an iPhone at the typical 12 inches from your eyes, that works out to 477 pixels per inch. At 8 inches it's 716 ppi. You have to hold it out 18 inches before it falls to 318 ppi.
So the iPhone has significantly lower resolution than the retina.
Sure, it's a good screen, but your eye is still a far better camera - and there's nothing that Steve Jobs' reality distortion field can do about that!
[UPDATE: I got this interesting email in from Gavin Stern, a medical student from NYMC that I thought would be interesting to share with you:
Overall, while technically the number of "pixels" for the new iPhone doesn't match what's on the retina itself, PRACTICALLY SPEAKING they probably tested what people could actually discriminate and those are the numbers they got.
There are many reasons why the number of receptors on the retina does not equal actual resolution:
-Convergence: cells in the retina converge and inhibit one another. You lose resolution there.
-Center-surround properties: those retinal ganglion cells inhibit one another. This increases contrast but you lose info.
-The layer of cells that overlies the photoreceptors causes chromatic aberration, mostly for blue-violet light. Subsequently, there are little to no blue cones in the center of the eye because of this.
-The eye is constantly moving to prevent photoreceptor cells from bleaching. You lose visual acuity here, but don't notice because the brain fills it in.
-There is more convergence of cells as visual information proceeds to the back of the brain, and then back up again for higher level processing
So maybe the iPhone screen is better than the human retina ... thanks for that Gavin!]