Debunking the Retina Display Myth

Last updated: August 10, 2014

Although Steve Jobs’ claims the human eye can’t perceive detail beyond 300 pixels per inch were immediately debunked, to this day almost everyone believes that what he said is still true. I became interested in this topic after seeing what I considered to be obvious differences between the highest-resolution smartphone displays. If Jobs’ claims were true, this shouldn’t have been possible. I wanted find out why I could see a difference, and whether it was possible to scientifically prove that Jobs’ retina claims were false. More importantly, I wanted to learn what specs would be needed in a real retina display. But before we can answer these questions, we need to go back to the beginning of this myth.

WWDC 2010 was where the Retina myth began

WWDC 2010 was where the Retina myth began

Looking Back

Back in June of 2010, Apple introduced the iPhone 4. Although no one knew it at the time, this would be Jobs’ last iPhone launch. The iPhone 4 was a landmark product because it was the first phone with a “Retina” display. Since few people correctly quote Jobs on this topic, let’s revisit what he said. Steve Jobs’ exact quote was “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.” This seemed plausible at the time because the display on the iPhone 4 was a big step forward. It had with four times the pixels of the previous model and a resolution of 326 pixels per inch (PPI).

Experts immediately questioned Jobs' retina claims

Experts immediately questioned Jobs’ Retina display claims

Experts Cry Foul

Almost immediately experts questioned Jobs’ claims. “Wired” ran an article saying the iPhone 4′s Retina display claims were “false marketing.” This article quoted Raymond Soneira from DisplayMate Technologies, who is one the most respected names in display analysis. Soneira said, “The math just doesn’t add up,” and suggested the term Retina display was misleading. Soneira went on to say “it was inaccurate to measure the resolution of the eye in terms of pixels.” He added “…a more accurate Retina definition would have a pixel resolution of 477 pixels per inch at 12 inches.”

Soneria was the first to attempt to prove Jobs was right

This blogger was the first to attempt to prove Jobs was right

Bad Math?

A blogger named Phil Plait then redid Soneira’s equations based normal vision, instead of perfect vision. Based on these calculations, Plait suggested Jobs’ claims were vindicated, but when you refer back to Jobs’ original quote, he refers to a distance of 10 to 12 inches. Plait conveniently used twelve inches, because that created the response he was looking for. Using a distance of ten inches, Plait confirmed that someone with normal vision could see visible pixels on a Retina display and the Retina display myth was busted. But that wasn’t the only problem with Plait’s and Soneira’s logic. There were several other problems we’ll discuss next.

A Flawed Definition of Perfect Vision

If you carefully read Plait’s article, you’ll see that he admits someone with perfect eyesight would be able to see a pixilated image when holding a Retina display one foot from their eyes. This backs up Soneira’s claim that 300 pixels aren’t enough for a true retina display, but there several problems with the definition of perfect vision. First, it is inaccurate to refer to 20/20 vision as “perfect” vision. 20/20 vision does not correspond to the best possible vision found in humans. Second, the word perfect doesn’t really make sense when applied to eyesight. The maximum acuity of a healthy human eye is 20/16 to 20/12. Even those with “bad” eyes can have 20/15 (or better) vision with glasses. This in itself doesn’t mean too much because the percentage of humans with better than 20/20 vision is relatively small (around 10-15% not including corrective glasses).

Most teens hold their phones close to their face

Most teens hold their phones closer to their face than adults

Screen Size Matters, Distances Vary

Contrary to the suggestions above, not everyone holds their mobile device 10 to 12 inches from their face. I’ve noticed that some teens hold their phones only 7 to 8 inches from their eyes. This is an important because the closer a person holds their screen, the higher the resolution required so the pixels effectively disappear. Jobs suggested that 300 pixels per inch was the magic number which determined whether a screen was a retina display, but the truth is there is no one single magic number for both smartphones and tablets. This is because the distance consumers hold tablets to their face is further away than they hold their smartphones. Some experts use a distance of 15 inches for tablets, but I often hold my tablet further away than that. What is the impact of this? It’s simple. The further you hold your device from your face, the lower the resolution needed for the pixels to disappear. This debunks the above assumptions that a single number can be used to determine whether a mobile device has a retina display or not.

20/20 has little to do with pixel recognition

Visual acuity alone is not the best predictor of pixel recognition

Primitive Measurements Don’t Cut It

The chart many eye doctors still use to determine whether you have 20/20 vision is a crude method that dates back to 1862. Eye charts were created to test vision, but we’re talking about something that goes beyond just text. We’re trying to determine whether a human can see the pixels on a display — and more importantly whether there is a benefit of using displays with resolutions higher than 300 PPI.

When trying to scientifically determine whether our eyes can tell the difference between two things, our eyes do a much better job telling the difference between two lines than they do interpreting characters of the alphabet. How much better? It turns out the ability of humans to distinguish between two different lines is actually ten times greater than 20/20 visual acuity. This is referred to as Vernier acuity and is the reason a Vernier scale like the one shown below allows users to measure things more precisely than using a uniformly-divided straight scale. You can prove this to yourself by taking this simple yet ingenious online test. This test proves that differences between Vernier lines can still be judged when the gap of a so-called “Landolt C” can no longer be recognized. In most cases the difference between these two is very large. That means while someone with excellent vision cannot recognize the orientation of the small “c” on the right (which has a 0.5 pixel gap size at normal reading distance), they can distinguish the gap between two lines that are only 0.05 pixels apart – that’s a 10x improvement.

The Vernier caliper uses Vernier acuity for more precise measurement

The Vernier caliper uses Vernier acuity for more precise readings

Science Still Matters

None of the experts quoted above attempted to scientifically test their assumptions. Plait claims his work calibrating for the Hubble telescope made him an expert in ophthalmology, but his real claim to fame was debunking the Moon landing hoax. I wondered what a real expert would say about this topic, so I did some research and found a study by Michael Bach. Mr. Bach is a professor at a German university known for their Ophthalmology-related studies and the former president of the International Society for Clinical Electrophysiology of Vision. Bach set out to test the limits of human vision and the ability to discern differences in extremely high-resolution displays. What he found and published in a scientific journal earlier this year clearly debunks Jobs’ retina display claims. His study had 49 subjects evaluate displays with resolutions between 254 and 1016 pixels per inch. The results of this study proves people can see the difference between a 339 PPI display and a 508 PPI display. More surprisingly, his study also suggests that some people can also discriminate between 508 PPI and 1016 PPI displays. So it’s clear the human eye is capable of benefiting from displays with more than 300 pixels per inch, but what is the minimum size for a true retina display and when will we be able to buy one?

The Real Retina Numbers?

Using the same equations Soneira and Plait used, a leading display manufacturer suggests a true retina smartphone display would need to have a resolution of at least 573 pixels per inch. However, this is for someone with perfect vision. The number is lower for someone with average vision. For a tablet held fifteen inches away from your eyes, and using the same equations, a true retina display would need a resolution that is higher than 382 PPI. Sadly, that means for people with perfect vision there are no true retina display smartphones or tablets available today. Even the new iPad Air only has a 264 PPI display. That doesn’t mean it doesn’t have a great looking display, but it doesn’t meet the definition of true retina display for a person with average vision.

Notice how the pixels of these four flagship phones vary

Notice how the pixels on four flagship phones vary. Source: AnandTech

All Pixels Are Not The Same

Now that we’ve established numbers for a true retina display, I want to point out one potential problem. When a mobile display goes under a microscope, it’s easy to see major differences between the types pixels used. The size varies, the shape varies, the placement varies. Even the color varies because some displays are now including white pixels (in addition to RGB). Some have pen-tile displays, others don’t. Even the type of displays used on popular smartphones vary. Companies like Samsung use OLED displays, while Apple uses LCD displays. Each has its own advantages and disadvantages. You can even see differences in the pixels on Samsung phones that have Super AMOLED displays. Unfortunately this topic is outside of the scope of this article. Just understand that all pixels are not the same and this makes it harder to come up with a single retina number that applies to all smartphones (or tablets). Other factors come into play as well, like the quality of your display. The better the quality panel, the more likely you are going to be able to see the differences we are discussing here.

Samsung recently shared their screen roadmap with analysts

Samsung recently shared their screen roadmap with analysts

Can You Really See A Difference?

Whether you can see a difference between your current smartphone and a smartphone with a true retina display depends on what you are viewing. Low-quality videos like the ones we watch on YouTube, will continue to look bad. In fact, they will even look worse, because you’ll see the compression artifacts more clearly. Small text is one area where you are likely to notice a difference. Text will be razor sharp. You can really see the difference between a 300 PPI display and 550 PPI display when things like pen-drawn Kanji characters are displayed. True retina tablets with screens that are 12 inches or larger will make it possible to get a newspaper-style experience, without reformatting articles. You will also be able to always use the full desktop versions of all websites and view high-resolution photos and 4K video with no loss of resolution. That’s not important today, but it will be in the coming years.

Much higher quality displays are coming in 2014

Much higher quality displays are coming in 2014

So When Can I Buy One?

True retina displays that are better than any Apple product are available now. The LG G3 has a 2560 x 1440 pixel smartphone display with a pixel density of 534 ppi. The Samsung Galaxy S5 LTE-A has a 5.1-inch display with an incredible 576 pixels per inch. That’s higher than the number required for a true retina smartphone display. Sadly it’s only available in Korea at this time. Samsung is also planning a 4K screen for smartphones. Assuming a screen size of around 5 inches, that works out to be about 880 pixels per inch.

4K tablet screens are coming as well. These screens should have resolutions over 400 pixels per inch, which exceeds the 382 PPI number required for a true retina display. Qualcomm demonstrated the first 4K Android tablet back in February of 2014. Reviewers like this one claimed its 3840-x-2160 display “easily beat the performance of the iPad Air.”

The Bottom Line

  • Researchers have proven people can see the difference between a >508 PPI display and a 339 PPI display.
  • It’s impossible to create a single number definition for a retina display because that number changes depending on the distance, your vision and other factors. Smartphones and tablets with much higher resolution displays are available now.
  • Apple mobile displays are no longer the best. Experts say the Galaxy S5 is the best performing Smartphone display that they have ever tested. As a result, Apple will finally increase the resolution of their mobile displays later in 2014.
  • Whether you can tell the difference between these new displays and today’s best displays will depend on the panel quality, distance and type of media you are viewing, but you won’t need a scientist to tell you they look great. Tablets will benefit the most, because their resolutions were significantly lower than smartphones.
  • – Rick

    Copyright 2013-2014 Rick Schwartz. All rights reserved. Linking to this article is encouraged. This article includes my personal opinions and does not reflect the views of my employer.


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    About Rick E. Schwartz
    Rick Schwartz is successful mobile blogger from San Diego. He is currently working on next-generation mobile hardware and software. You can learn more about Rick by clicking on the "About" tab at the top of this page.

    10 Responses to Debunking the Retina Display Myth

    1. The responses to this article at the Google + Mobile Discussions page have been positive. I wanted to feature one comment that I found to be very interesting:

      “I have been in book production for 15 years now and we’ve only moved to digital printing techniques when the printers’ dpi rose to above 600. Under 1200 dpi you would see pixels in italics, especially in small print, like footnotes and superscript. Now you don’t have anti – aliasing in paper books (b/w) but still I don’t understand why people thought for so long that 300 dpi for screens would suffice where it clearly was not good enough for printing. Traditional printing is about 2400 dpi.”

      From: Pieter Lamers
      Yesterday 11:26 AM

    2. Panasonic also plans to ship a 4K tablet in January — although it’s very pricey ($6,000). This is why I didn’t include it in the main article. http://www.eweek.com/small-business/panasonic-toughpad-tablet-boasts-4k-resolution-display.html

      – Rick

    3. Pingback: Why You’d Still Have to Be Crazy to Buy an iPad Mini | Mostly-Tech

    4. standardpull says:

      It seems like you are cherry-picking your own sources and introducing your own biases. I really don’t mind that; everyone has an opinion. But sadly, others are using your article as if it is fact, where in reality it is just personal opinion.

      Kids learn about using appropriate sources in school. Journalists? Sometimes. Bloggers? Almost never.

      • Armando says:

        …Vernier acuity is not a matter of opinion, it’s fact!
        You seem to imply that the whole article is of personal opinion based on shady sources, whereas you present none to debunk it except your own obviously biased opinion.
        I could live without the companies roadmaps, market predictions and Jobs’s bashing, but higher smartphone resolutions definitely aren’t just a case of “the emperor’s new clothes”.

    5. SteveS says:

      This article clearly has a heavy bias and does cherry indeed cherry pick sources of information from experts. Moreover, it briefly touches on the notion that not all display technologies are the same, yet conveniently dismisses this notion as beyond the scope for this article.

      People that set out to “debunk” marketing claims need to do so in the proper context. During the iPhone 4 debut, Steve Jobs wasn’t submitting a paper for critical review. Rather, he was distilling a complex discussion / concept into language that common people can understand.

      From a technical perspective, I would agree that it’s incorrect to express visual acuity in terms of pixels. The important thing is whether or not what is being said is both reasonable and “in the ball park” so to speak. Job’s claim did include the notion of reasonable viewing distances and is likewise correct. If this claim was not correct, Apple would be obliged change their marketing message.

      It comes down to math…
      20/20 vision is defined as the acuity to discern a detail of 1 arc minute.
      Visual Resolution = (1 / Visual Acuity) * (1 / 60)
      Visual Resolution = (1 / (20 / 20)) * (1 / 60) = 0.0166667 degrees
      Pixel Size = 1 / PPI
      Pixel Size = 1 / 326 = 0.003067″ (iPhone pixel size)
      Distance = Pixel Size / (2 * Tan (Visual Resolution/2))
      Distance = 0.003067 / (2 * Tan (0.0166667/2)) = 10.54″

      Unless you’re able to challenge the definition of 20/20 vision, the iPhone has “Retina” (human 20/20 limits) at a distance of 10.54 inches or greater.

      What this article failed to address is the impact of lesser display technologies. For example, it’s commonly accepted that Pentile based displays require a higher PPI resolution to achieve equivalent sharpness. I don’t have the math on the exact details for this, but it does explain why some vendors need to go to a higher resolution in order to get a sharper display. It also helps them from a marketing perspective. More is better, right? That’s what this article apparently would like us to believe.

      • Thanks for the comment. I definitely don’t think that more pixels is always better. A good OLED display is superior in many ways to a non-OLED panel with the same pixels. My point is simple. Job’s quote may have been accurate, but it was misunderstood by many to suggest there is no reason to get a higher resolution display because your eye can’t tell the difference. That has been scientifically proven to be false.

        – Rick

        • Tiny Tim says:

          Sorry, but it has not been ‘scientifically proven to be false’ at all.

          If you have 20/20 vision, and you hold a device at 10.5 inches or more away from your face, retina PPI is sufficient. End of story.

          For those people, there IS no reason to get a higher resolution display.

          All you’ve done is said ‘for people with better than 20/20 vision or people who hold their phone closer, they can see pixels’. It’s a non argument.

          Jobs’ point is still correct.

    6. jason891107 says:

      As a user, what I truly care is, after Jobs stated that you cannot see pixels on iPhone 4 display, I stopped by at the apple store, closely stared at the display for like half minute and didn’t find pixel, and soon after that I got my first iPhone.

    7. Alex says:

      None of these retina articles take into account the subpixels. Anti aliasing means the real resolution is more like three times the pixel resolution.

      I agree if anti aliasing didn’t exist and only black and white pixels are displayed then you need around 700-900ppi but when you add in the subpixels that number drops to about 350ppi.

      I’m amazed that retina as a term is being taken so literally. I remember when you were lucky to get over 72ppi and for many years it didn’t change. It’s like the mega pixel myth in cameras, the numbers go up but the quality and real world improvements are so minimal or suffer in ways that a spec can’t. QHD on phones is not much of a bump in resolution yet people are praising it as some kinda of messiah!

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