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About the iPhone 4 Retina Display



Been reading through reactions on the iPhone 4 this morning. One topic of contention seems to be Retina Display. Will it shrink everything? Will it create problems for developers? Will the iPad get it? Short answer to all: no. Here’s why.

In the comments here and on other sites, a few people have questioned whether the increased resolution will actually make reading more difficult. I’m sure we’re all familiar with how increased resolution works on PCs. You bump up the resolution, everything gets smaller. Here at work, that keeps most people from running their displays at the highest resolution. However, that’s not an issue for the iPhone because it already scales things to fit the screen. For example, the iPhone shrinks websites to fit the small display. That will still happen even with the 960×640 Retina Display. The content on the display will retain the same physical dimensions, shrunk or stretched to fit the 3.5″ display, but with more pixels per inch.

I’ve also read a claim that the increased pixel density will be a problem for game developers. Something to do with frame rate, increased need for processing power, etc. Normally this would be a valid point, but not in this case. Why? Because the iPad already does fine with gaming on its 1024×768 display and A4 chip. The iPhone 4 actually serves up fewer pixels at 960×640 but uses the exact same chip. Physical dimensions aren’t a factor. Thus, games should run smoother on the iPhone 4 than on the iPad.

Finally, James Kendrick, among others, ponders whether the iPad will get the same pixel doubling treatment. I doubt it. First, the previous concern over pixels and processing power would apply here. Running a 2048×1536 display I’m sure would require more processing power than the A4 can comfortably support. Second, the doubled iPhone 4 resolution eliminates the need for pixel doubling when running iPhone apps on the iPad. Future iPhone apps will be able to run on the iPad at their native resolution without being absurdly small, allowing developers, particularly game makers, to focus on the iPhone. Doubling the iPad’s resolution would undo that, and I’m 94% sure this was a consideration in their decision to pursue Retina Display.

Of course, as technology progresses, processing power will increase, paving the way for another doubling of pixels. But for the next couple of year sat least, I think we’ll be looking at the Retina Display only on the iPhone (and presumably iPod touch), not the iPad.



  1. aftermath

    06/09/2010 at 11:04 am

    Why are you calling this pixel doubling? You haven’t doubled the pixels. You’ve doubled the PPI (pixels per inch). If you double the lengths of the sides of a rectangle you quadruple the area. The PPI has doubled, but there are four times as many pixels. Game developers SHOULD be concerned. If you developed your game so that you’re currently maxing out the hardware to achieve your current framerate, then having to toss around 4 times as many WILL cause the framerate to drop.

    Generally speaking, the unaided human eye can’t differentiate detail beyond 300 PPI (pixels per inch). This new phone’s PPI is above that threshold. Interestingly, 3 years ago the Toshiba Portege G900 was the first phone to exceed this (not to imply that Apple is copying an innovation from a three year old Toshiba phone that nobody bought because it was a terrible product). I don’t believe that the ipad could handle a PPI bump that also exceeded 300 PPI. Forget PPI for a second, and just think about image quality itself. Currently, the ipad screen offers a 0.78 megapixel display (which is a head scratcher for something which is supposed to be a visual content consumption platform). A doubling of the PPI and a quadrupling of the pixels would lead to a 3.1 megapixel display. That’s great, but a 1080p panel is only 2.1 megapixels. Apple might want to just try getting there first before trying to surpass 300 DPI so that they can use the word “Retina” in their marketing. (As an interesting corollary, 1080p at 300 PPI happens on a 7.3 screen. That would be a much better device than the current ipad all the way around.)

    • Sumocat

      06/09/2010 at 12:37 pm

      Sorry, pixel quadrupling is correct. Pixel doubling is the term for running iPhone apps on the iPad at double their dimensions.

      Regarding game developer concern, there’s no cause for it. Any games currently developed are running on the previous processor with the old resolution, so they’re running well below the limits of the iPhone 4. The iPad runs the same A4 chip and offers around 25% more pixels, so even new and updated iPhone 4 games will run below the pixel display max. The iPad already proves that games and apps can run smoothly while displaying more pixels than the iPhone 4 allows.

      • Frank

        06/09/2010 at 2:53 pm

        what you said doesn’t make sense.
        Just read aftermath’s post a second time.
        Game designers design their games, so that they run smooth with max. quality on current hardware. If you keep the processing power almost constant, but quadrouble the resolution, then the game can’t run smooth any longer. It’s physically impossible! Except the game still runs on the old resolution and just gets rezized.
        Most likely this happens, especially because all textures are rendered for the low resolution. Sadly, this also means that the game looks as good/poor on the iPhone 4 as it looked on the iPhone 3. No change at all.

        • Sumocat

          06/09/2010 at 3:28 pm

          IF you keep the same hardware, but it’s not the same hardware. The iPhone 4 runs the A4. The 3GS runs a slower system. That’s the system existing games are maxing out. They haven’t had a chance to max out the A4 yet, except on the iPad and the A4 seems to be keeping up fine with its higher pixel count.

        • Tim

          06/09/2010 at 3:39 pm

          To state Sumocat’s point another way: Take a game maxxed out for an iPAD (not phone) and scale it down ~25%. That’s this system.

          Basically, the performance has *more* than quadrupled (at least in draw power).

  2. Ben

    06/09/2010 at 4:04 pm

    “I’m sure we’re all familiar with how increased resolution works on PCs. You bump up the resolution, everything gets smaller.”

    No, that’s NOT how PCs work if you’ve upgraded from that pos XP. Windows Vista and 7 have no major problem with high dpi displays for applications that use WPF.

    • Sumocat

      06/09/2010 at 5:37 pm

      So then why does everything on this Windows 7 PC get bigger when I decrease the resolution then shrink when I increase it back?

      • Scott

        06/09/2010 at 9:43 pm

        It depends if you have a CRT, or an LCD. An LCD has a set number of pixels. A CRT does not.

        If it’s a CRT, everything gets smaller like Sumocat says. On an LCD everything will stay the same size.

      • Ben

        06/10/2010 at 12:22 am

        Because you likely adjusted the resolution without adjusting the DPI setting. If your screen’s native resolution is, say, 1440×1050 and 12 inches (like my x61t), then it has a DPI of 144. If I then change the resolution to, say, 800×600, but don’t change the physical screen size (which is obviously unlikely), then the DPI according to your settings is 82. But if your DPI setting remains untouched, things appear too big or too small.

        If you set windows 7’s DPI setting to your screen’s native DPI AND your resolution setting to the screens native resolution, then 1 inch on the screen (for example, in Word’s ruler) will measure 1 inch.

        So, if I create a program and set the window’s size to the equivalent of 4in x 3in, it’ll appear that size on a 12 inch or a 24 inch screen in win7 with correct settings.

        In XP and before, the old window drawing system didn’t support DPI scaling with the same ease. Programmers could enable such support in their programs, but most didn’t. That’s why if you ever adjusted the DPI everything got screwed up. So you were effectively stuck at the default setting of 96 dpi. If you then had a screen that wasn’t 96 dpi, it would look “small” or “large”.

        People mistook this as “screen real estate”. It’s not. The only true way you can increase screen real estate is to buy a larger monitor. But people noticed that you can fit more into such incorrectly calibrated screens at the expense of size. Good for people who don’t mind “everything tiny”, but it caused a common misconception that high resolution = “everything tiny”.

        That misconception (in addition to cost and some other technical factors) is, I believe, we haven’t seen many high DPI screens available for desktop and laptop systems. Most screens available now are around 110-130 dpi. Compare that to 160+ screens now commonly available in smartphones.

      • Ben

        06/10/2010 at 12:36 am

        Furthermore, from my experience, web browsers don’t really account for DPI, which is why even if windows 7’s programs display correctly, webpages may still look “small” on high DPI screens. Lots of webpages have hard-coded sizes for their width, which is why you may see a lot of blank space around the main content of a page. The browser is interpreting the CSS’s 1024px width setting as physical screen pixels instead of “resolution independent” pixels, which ignores the DPI scaling that windows 7 (etc) can perform.

        Some programs can still suffer from this sort of problem if they are drawing their own windows and bypassing whatever magic WPF uses to create resolution independence. I think, for example, photoshop’s gui suffers from that problem (at least it seemed so the last time I tinkered with it). Even some of MS’s own programs (like the windows live installer) don’t work 100% correctly.

        • Sumocat

          06/10/2010 at 3:58 am

          Long story short: increase resolution, everything small; increase dpi, everything big (with exceptions).

          • Ben

            06/10/2010 at 6:16 am

            Actually: Long story short, use the wrong settings, everything small or large; use the right settings, everything fine.

  3. Virtuous

    06/09/2010 at 4:21 pm

    In a couple weeks we’ll know for sure when iPhone 4 ships.

  4. Gordon

    06/10/2010 at 12:54 am

    Interesting that SJ believes that the extinction point of human vision is 300 ppi. I’m a working photographer and fine art printer and for the last 20 years I’ve been taught that it’s between 180 and 240 ppi at 12 inches. Depth of field and circle of confusion calculations are also based on 180ppi as the limit of human vision. Wonder where he got his information from?


    • Tim

      06/10/2010 at 10:54 am

      Perhaps it’s just measured at less distance away? I imagine the last thing he would want is to have a “retina display” (side note, can we stop calling it by Apple’s branding of it, it’s just a high DPI screen) that people held up to their face and went I CAN SEE THE PIXELS LIAR!

    • John Morrison

      01/13/2011 at 5:32 am

      My guess is SJ used similar calculations as you but at a closer distance.

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