Monday, June 28, 2010

Iphone 4S Not really 'Retina' display

I found this article at Yahoo news (from Christopher Null  - he is avery good technlogy writer) where Raymond Soneira is explaining that the retina display is not better than average human vision. Discovery Channel did say differnet but i like his statement more. But i guess at the end counts that the iPhone has the best display so far.
Steve Jobs' statement on the "Retina Display" when announcing the iPhone 4 at WWDC: "It turns out there's a magic number right around 300 pixels per inch, that when you hold something around to 10 to 12 inches away from your eyes, is the limit of the human retina to differentiate the pixels."

I used the accepted value for the visual acuity of the Retina (see below) and found that the iPhone was more than a factor of 2 short on pixels to be a Retina Display. The iPhone 4 would need to have 1.3 megapixels instead of 0.6 megapixels to be a true Retina Display at 12 inches. At 10 inches it would need even more - 1.9 megapixels - a factor of 3 short.
There have been some comments that my analysis is for perfect vision. Jobs' statement is for the *Retina* not the *Eye* with 20/20 or other vision. For 20/20 vision the accepted value is to resolve two lines that are separated by 1.0 arc minute. In that case a 20/20 vision display needs a resolution of 286 dpi or higher at 12 inches and 344 dpi at 10 inches. The iPhone 4 has 326 dpi, so at 12 inches it is a 20/20 Vision Display but not a Retina Display.

In fact, there are lots of people who have better than 20/20 vision, for example, 20/10 vision is twice as good as 20/20. I had 20/10 vision until I was 20 years old and corrective lenses can provide 20/10 vision for many people. For 20/10 vision the acuity is 0.5 arc minutes, which is actually smaller than the value used for the Retina, so at 12 inches an iPhone 4 is not a 20/10 Display nor a Retina Display.

One article examining my results that got a lot of attention was by Dr. Phil Plait on Discovery He is an astrophysicist and verified my calculations but concluded that while I was technically correct I was being very picky and my results only applied to people with perfect vision - by that he meant 20/20 vision, which is nominal good vision, but not 20/10 vision, which is considered perfect vision. My point is actually that specs have to be picky.

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 Display - but it's good enough for 20/20 vision when held at 12 inches or more from the eye. 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.

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