Resolved Please explain this retina display thing

Discussion in 'iPad' started by ThatsMeRight, Mar 14, 2012.

1. Mar 14, 2012
Last edited: Mar 14, 2012

ThatsMeRight macrumors 68020

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Sep 12, 2009
#1

I just don't get it. What are the calculations? What do you fill in?

How do you determine if a display is 'retina qualified' or not?

Edit: there seems to be a misunderstanding. I definitely understand what a "retina display" is, but I want to know how you can calculate whether a display is a 'retina display' or not?

Example.

How can I figure out whether a 20 inch display with a resolution of 1920 by 1080 with an average viewing distance of 20 inches is a retina display?

(Just like that a 3.5" display with a resolution of 960 by 640 at a distance of 10 inches is a retina display).
(Just like that a 9.7" display with a resolution of 2048 by 1536 at a distance of 15 inches is a retina display).

How do you calculate it?

2. DenisAuermann macrumors regular

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Feb 16, 2012
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#2
Basically retina display are a combination between pixel density and how far away you're viewing it. I think it's mainly applies for mobile devices that you hold close to you. I can't see any pixels on my 42 led HDTV but that hardly makes it a retina display.

It's basically the inability to distinguish single pixels on iPhones or Ipads when you hold them at an average distance

3. SuperRob macrumors 6502

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Mar 14, 2011
#3
Retina Display is whatever Apple wants to call it, first and foremost. It's a marketing name. Further, it's any display where the pixel count is quadrupled over a previous "standard" display, making it easy to simply "pixel double" images and not lose lose quality when viewed on such a display.

But science-wise, it's a display with a high-enough pixel density that you cannot distinguish individual pixels from a reasonable viewing distance. Maybe there's a mathematical formula for it, maybe there isn't. In the end, it doesn't matter, because each person is different. Just know that it's the second highest DPI screen on a device that Apple has ever shipped (second only to the Retina Display on the iPhone 4/4S).

4. ThatsMeRight thread starter macrumors 68020

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Sep 12, 2009
#4
I definitely understand what a retina display is, but thanks for the explanation anyway.

What bothers me, is that I can't figure out how you can calculate when a display is 'retina qualified' or not.

How do you use the formula? What are you going to fill in? And how are you going to know if a display is 'retina qualified' or not based on the solution of the calculation?

Example.

How can I figure out whether a 20 inch display with a resolution of 1920 by 1080 with an average viewing distance of 20 inches is a retina display?

(Just like that a 3.5" display with a resolution of 960 by 640 at a distance of 10 inches is a retina display).
(Just like that a 9.7" display with a resolution of 2048 by 1536 at a distance of 15 inches is a retina display).

How do you calculate it?

----------

There is a mathematical formula (like shown in the image). I just don't understand how to use this formula (see my comment above).

5. QuarterSwede macrumors G3

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Oct 1, 2005
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#5
Here is a good TUAW article on the formula. When I watched the Apple keynote I about choked as I knew exactly where that formula had come from (either that or TUAW did some really good research).

6. yippiekiyay macrumors newbie

Joined:
Apr 4, 2011
#6
not positive, but i'd guess the area of focus on the eye is 2 times the tan inverse of the height of a pixel divided by twice the distance of viewing, the angle of focus worked out by pythagorus i'd imagine

i'd also also say that the equation given by apple will prob be assuming average eyesight of 20:20.

it does just sound like marketing, but i still remember being impressed with my iPhone retina display nonetheless and expect the same on friday.

i will freely admit that i could be talking nonsense and i probably am

7. DenisAuermann macrumors regular

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Feb 16, 2012
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#7
Yeah it's really annoying

I found this tough

http://bhtooefr.org/displaycalc.htm

8. ThatsMeRight thread starter macrumors 68020

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Sep 12, 2009
#8

I've chosen for "Distance (useful for existing monitors)". This is my input: a resolution of 2048 by 1536, 9.7" size and 20/20 visual acuity.

As output, it gives a distance of 13.026796874999999.

So, if I understand it correctly, the third generation iPad is truly a retina display when hold at a distance of 13.027 inches?

If this is correct, than I thank you a lot!

9. frumpsnake macrumors member

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Dec 30, 2008
#9
Sounds correct. The TUAW article says the new iPad at 16" would be 123% Retina which is 16/13.

10. Dr McKay macrumors 68040

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Aug 11, 2010
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Kirkland
#10
Retina is simply a pixel density. Also they take into account the viewing distance. I'd say retina is really when a device has such a pixel density that from average viewing distance the human eye cannot distinguish individual pixels.

11. striker33 macrumors 65816

Joined:
Aug 6, 2010
#11
Its a marketing term. Dont take it too literally.

The fact that everyone has different armspans, its impossible to determine the exact distance at which pixels are indistinguishable.

Considering I cant see any pixels on my 27" iMac at around 5 inches more than Apple's method with the new iPad says it all.

12. DreamPod macrumors 65816

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Mar 15, 2008
#12
Yeah, there is no formula you can apply to determine if something is a "retina display" or not. Apple calls whatever they want a retina display, it is their trademarked buzz word, surrounded by a bunch of jargon and hype. At the time of the iPhone 4 release, Apple would have said that a DPI as low as the iPad 3 could never be called a Retina Display.

13. GroundLoop macrumors 68000

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Mar 21, 2003
#13
Correct. As long as the average distance from your eye is 13.027 inches or greater, you will not be able to see individual pixels.

GL

14. DanBurns91 macrumors regular

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Jan 25, 2012
Location:
West Midlands, England
#14
3rd highest display, the Sony Ericsson Xperia S has more pixel density than my beloved 4s

15. GroundLoop macrumors 68000

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Mar 21, 2003
#15
This is not correct. The calculator posted earlier in this thread is the true math used to determine if a device can be considered "retina" (aka indistinguishable pixels) using the input data. If you hold your iPad at 12", then the 3rd Gen iPad is NOT retina for you.

This formula is commonly used for engineers working on visual systems required to meet 20/20 visual acuity.

GL

16. DreamPod macrumors 65816

Joined:
Mar 15, 2008
#16
"True math" to determine if Apple can call something by their trademarked buzzword that no other company can legally use? And you're saying that every person in the world has the exact same eyesight?

17. ThatsMeRight thread starter macrumors 68020

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Sep 12, 2009
#17
Thank you all for your feedback and confirmation.

http://bhtooefr.org/displaycalc.htm

This seems to be the best tool for me. You choose for the first open (distance), fill in the resolution, fill in the screen diagonal and fill in the visual acuity (20/20). It will automatically give you the pixel density (which is not really hard to calculate) and it will give you the minimum viewing distance for a display to be 'retina display'.

Oh, and yes people - I do know that Apple is using "retina display" for marketing, but there actually is some logic behind it: you can actually calculate when you are unable to distinguish individual pixels at a certain distance.

18. GroundLoop macrumors 68000

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Mar 21, 2003
#18
No. The assumption that Apple uses is 20/20 eyesight. if you have 20/10, then you need to use the calculator posted earlier in the thread. Don't take Apple's word if a display is retina or not, but the calculator can tell you if it is for your specific set of circumstances (eye site, average distance from eye, etc)

GL

19. SuperRob macrumors 6502

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Mar 14, 2011
#19
What I said was ...