I recently stumpled upon an android tablet claimed featured with a retina screen with 2048 x 1536 pixels, I have never heard of that android tablet have a retina screen because its price is high. Retina means screen with ppi above 300, which is the most detailed picture naked eye can see. iPhone 4 made with a IPS screen with 960 x 640 pixels, there is a formula to help you work out its ppi

This figure out iPhone 4 PPI is 330, a little different from 326 that official give, I am confused.
Another, all screens woth ppi above 300 can be called retina? Or Retina means a technique Apple own to optimize on ppi base?

For practical purposes, and the way Apple uses it, Retina means that a person with average vision can not distinguish individual pixels a the normal viewing distance for that device. There is no set PPI that defines whether a device is Retina or not.

That means that while the 3rd gen iPad has fewer PPI than the iPhone 4 and newer, it is still considered Retina; because the typical viewing distance is is further away.

To the best of my knowledge Apple does not own any rights to the designation Retina display, nor is their definition the only possible one.

Quite a few experts have played the math game with the Retinal designation. Reading several of them has led me to the non-conclusion that it all depends on how you look at it.

Any screen resolution with a pixel density high enough so the human eye cannot distinguish individual pixels fits Apple's self-definition of Retina Display.

Most 1080p monitor are retina displays because most people view them from 2+ ft away.

I believe 'Retina' is Apple marketing speak. A trade name they made up to set their screen apart from the rest.

Originally Posted by Bob Maxey

I believe 'Retina' is Apple marketing speak. A trade name they made up to set their screen apart from the rest.

Retina is not an Apple trademark, it can be freely used by any company to describe their high resolution displays.

Originally Posted by scifan57

Retina is not an Apple trademark, it can be freely used by any company to describe their high resolution displays.

Actually . . .

"On June 11, 2010, the US Patent & Trademark Office published Apple's latest trademark application for "Retina" under applications 85056807 and 85056810. Apple has filed their trademark under two distinct International Classes covering such matters as electronic hand-held game units and cell phones. Apple's CEO Steve Jobs stated in their June 7, 2010 press release that "Apple's stunning 3.5 inch Retina display has 960 x 640 pixels—four times as many pixels as the iPhone 3GS and 78 percent of the pixels on an iPad. The resulting 326 pixels per inch is so dense that the human eye is unable to distinguish individual pixels when the phone is held at a normal distance, making text, images and video look sharper, smoother and more realistic than ever before on an electronic display."

I quite frankly do not know who owns the word Retina. A Google search provided the above quote from PatentlyApple dot com. I do not know the history of the word as it applies to Apple displays and I do not care. Just answering the OP's question, "What is Retina?"

By the way, they also own Carbon, Chicago, Boot Camp, Cinema Tools, Cocoa and a large list of many more, just like Microsoft, Harley-Davidson, Ford and 3M..

Are you thinking it is a generic term to define a part of the eye and therefore, anyone can use it? I use a generic fruit called an Apple. Let's just see me try to use that generic term and a picture of an Apple to name my computer company.

Originally Posted by Bob Maxey

Actually . . .

"On June 11, 2010, the US Patent & Trademark Office published Apple's latest trademark application for "Retina" under applications 85056807 and 85056810. Apple has filed their trademark under two distinct International Classes covering such matters as electronic hand-held game units and cell phones. Apple's CEO Steve Jobs stated in their June 7, 2010 press release that "Apple's stunning 3.5 inch Retina display has 960 x 640 pixels—four times as many pixels as the iPhone 3GS and 78 percent of the pixels on an iPad. The resulting 326 pixels per inch is so dense that the human eye is unable to distinguish individual pixels when the phone is held at a normal distance, making text, images and video look sharper, smoother and more realistic than ever before on an electronic display."

I quite frankly do not know who owns the word Retina. A Google search provided the above quote from PatentlyApple dot com. I do not know the history of the word as it applies to Apple displays and I do not care. Just answering the OP's question, "What is Retina?"

By the way, they also own Carbon, Chicago, Boot Camp, Cinema Tools, Cocoa and a large list of many more, just like Microsoft, Harley-Davidson, Ford and 3M..

Are you thinking it is a generic term to define a part of the eye and therefore, anyone can use it? I use a generic fruit called an Apple. Let's just see me try to use that generic term and a picture of an Apple to name my computer company.

Apparently that while they have applied to trademark the term retina display, I can't determine whether the trademark application has yet been approved.

Originally Posted by wosiccp

I recently stumpled upon an android tablet claimed featured with a retina screen with 2048 x 1536 pixels, I have never heard of that android tablet have a retina screen because its price is high. Retina means screen with ppi above 300, which is the most detailed picture naked eye can see. iPhone 4 made with a IPS screen with 960 x 640 pixels, there is a formula to help you work out its ppi Attachment 27782

This figure out iPhone 4 PPI is 330, a little different from 326 that official give, I am confused.
Another, all screens woth ppi above 300 can be called retina? Or Retina means a technique Apple own to optimize on ppi base?

Do not be confused. all you need to know is if you must make a choice between something marked Retina and something marked Hercules, go with Retina.

As for the math, that is all well and good, but I know someone that cannot tell the difference between his old TV and his new 1080P screen. Old farts like me and a few of you younger folks often see things differently and the math really does not matter. For me, the iPad one's display is good enough.

Originally Posted by Bob Maxey

Actually . . .

"On June 11, 2010, the US Patent & Trademark Office published Apple's latest trademark application for "Retina" under applications 85056807 and 85056810. Apple has filed their trademark under two distinct International Classes covering such matters as electronic hand-held game units and cell phones.

I stand (sit actually) corrected. Or at any rate acknowledge that I am at least partially in error.