An article published by Wired.com last week about the accuracy of Apple’s iPhone 4 “retina” display claims has stirred some debate, provoking a response from Phil Plait of Discover.com.
In his keynote speech presenting the iPhone 4, Jobs said the handset’s display had a pixel density of 326 pixels per inch, exceeding the limit of the human retina.
Soneira contends that the iPhone 4 has significantly lower resolution than the retina, and he has requested for Wired.com to publish a statement clarifying his claims. Below is his statement in full:
The iPhone 4 has an outstanding display, and I’m glad that Apple resisted the emotional rush to OLEDs because they still need lots of improvement before they will be ready to compete with the highly refined IPS LCDs. The iPhone 4 display should be comparable to the outstanding IPS LCD in the Motorola Droid, which I tested and compared to the Nexus One OLED, which was trounced by the Droid.
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 – the accepted value is 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 it would need to be 477 pixels per inch to be a retina limited display. At 8 inches it would need to be 716 ppi. You have to hold it out 18 inches before the requirement falls to 318 ppi. The iPhone 4 resolution is 326 ppi.
So the iPhone 4 has significantly lower resolution than the retina. It actually needs a resolution significantly higher than the retina in order to deliver an image that appears perfect to the retina.
The iPhone 4 is a great display, most likely the best mobile display in production (and I can’t wait to test it) but this is another example of spec exaggeration, an industry trend I wrote about in my Maximum PC piece “Display Myths Shattered.”
Examining this issue more closely, the iPhone 4 is actually very far from a retina display – it’s a substantial discrepancy and not even close: At 12 inches the 1 dimensional linear ppi shortcoming is 326/477 = 68 percent. But the pixel (area) density for 2 dimensions, which is the actual relevant observable, is that value squared = 0.47, so the iPhone 4 is more than a factor of 2 from being a retina display at the typical 12 inch viewing distance.
Stated another way the iPhone display would need to have 1.3 megapixels instead of 0.6 megapixels to be a true retina display at 12 inches.
There have been some comments that my analysis is for perfect vision. Jobs’ statement is for the retina â€” not the eye with a poor lens. If you allow poor vision to enter into the specs then any display becomes a retina display. That turns it into a meaningless concept that will be exploited by everyone. The iPhone 3GS (and any other display) can then be called a retina display for the percentage of the population with poor vision.
Specs need to be objective, precise and accurate. Allowing puffery and exaggerations in the sales and marketing starts a snowballing effect that eventually leads to the 1000 percent rampant spec abuse that I document for displays. The iPhone 4 is a fabulous display, it’s just not a retina limited display. Since Apple makes great products that have excellent specs it will be a lot better for them if everyone sticks with the true objective values instead of values exaggerated by marketing departments.
Dr. Soneira is president of DisplayMate Technologies and a recognized expert in display technology. He has a PhD in theoretical physics from Princeton University and was a long-term member of the world-famous Institute for Advanced Study in Princeton (the Einstein Institute). He has also done extensive work in astrophysics including the Space Telescope with John Bahcall, who was the prime mover in the development of Hubble.
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Photo: Jon Snyder/Wired.com
Read the original post:
Display Expert: iPhone 4 Resolution â€˜Significantly Lowerâ€™ Than Retina
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