The display will play a central role in the marketing, appearance, and performance of the iPhone 5, which will be announced on Wednesday September 12. The iPhone 4 display is no longer state-of-the-art. While I don't have any inside information about the iPhone 5 display, below are a series of Sherlock Holmes deductions based on existing information and trends from the iPhone 4 and the latest competing smartphone displays. The iPhone 5 will need to meet most of these goals in order to retain its number 1 ranking. These same display goals apply to any smartphone that wants to be a 1st tier smartphone.
Dr. Raymond Soneira of DisplayMate Technologies has made it his mission to suss out the best smartphone, tablet, HDTV, and multimedia displays from the worst with his Display Technology Shoot-Out series. Now, he cooks up a few predictions for what the iPhone 5 display might be like.
The aspect ratio (screen width divided by its height) for the iPhone 4 is 3:2. For the iPhone 5 the rumor mill has settled on 16:9, the same as HDTVs and most video content. This looks like an excellent bet, so we'll work with that...
1st Tier Smartphone Goal and iPhone 5 Best Guess: 16:9 Aspect Ratio.
The current iPhone 4 screen resolution is 960x640 pixels. In order to maintain compatibility with existing Apps the iPhone 5 can't stray too far from this. Since the aspect ratio is increasing from 3:2 to 16:9 the best guess is that the iPhone 5 will keep the same 640 pixels and just increase the 960 pixel value based on the new aspect ratio. In that case the screen resolution will be 1136x640 pixels. That's 176 more vertical pixels, so existing apps expecting 960x640 will simply be letterboxed with 88 pixel black borders on the top and bottom. But since we are already letterboxing, why not raise the 640 pixel base up to 720 pixels and add 40 pixel black borders there as well? Even better... 720 pixels is true HD high definition - that is not only a major marketing advantage but there is much less processor overhead (and battery power) from rescaling content from 1080p to 720p than to 640p (rescaling by 3/2=1.50 rather than by 1.69). While the Samsung Galaxy S III and Galaxy Nexus have 1280x720 pixels they are PenTile displays so they aren't as sharp as true RGB 1280x720 displays.
1st Tier Smartphone Goal and iPhone 5 Best Guess: 1136x640 pixels - but 1280x720 pixels (true HD) would be much better.
PPI Pixels Per Inch
The higher the pixels per inch PPI the sharper the image on the screen, but what really matters is the sharpness perceived by your eye and that depends on the viewing distance from the screen (and also how good your vision is compared to 20/20 Vision). So PPI cannot be used by itself, but must be used together with the viewing distance in order to draw any conclusions about visual sharpness, and whether or not it qualifies as a Retina Display. Apple's Retina Display criterion is based on 20/20 vision. The iPhone 4 has 326 PPI and it appears perfectly sharp for 20/20 vision down to a viewing distance of 10.5 inches. The new iPad 3 has a lower 264 PPI, but it is still a Retina Display because it appears perfectly sharp for 20/20 vision down to a viewing distance of 13.0 inches, which is less than its typical viewing distance. To be a Retina Display down to a viewing distance of 12.0 inches the display needs 286 PPI or more.
1st Tier Smartphone Goal and iPhone 5 Best Guess: 326 PPI, but it can go down to 286 PPI and still be a Smartphone Retina Display.
The Screen Size will depend on the screen resolution and pixels per inch. If the iPhone 5 keeps the same 326 PPI as the iPhone 4 and has 1136x640 pixel resolution, then the screen size will be 3.96 inches, an 18.5 percent increase in the area of the screen (the diagonal size increases by 13 percent). But with Steve Jobs' 300 PPI value, the screen would be 4.35 inches. Using 286 PPI, the screen would be 4.56 inches and remain a Retina Display down to 12.0 inches viewing distance. Finally, with a resolution of 1280x720 and 326 PPI the screen would be 4.5 inches. So there is lots of room for a smartphone Retina Display up to 4.5 inches.
1st Tier Smartphone Goal and iPhone 5 Best Guess: 4.0 inches, but could go as large as 4.5 inches and still be a Retina Display.
Most smartphones are used in reasonably bright ambient lighting. Reflections from the screen not only decreases picture quality but it makes the screen harder to read and causes eye strain. We measured the iPhone 4 reflectance at 7.0 percent, but many mobile displays now have reflectance values much lower than that. The current record holder is the Nokia Lumia 900, with a screen reflectance of 4.4 percent - so the iPhone 4 reflects 59 percent more light than the Lumia 900. The iPhone 5 needs to do a lot better...
1st Tier Smartphone Goal and iPhone 5 Best Guess: Reflectance under 5 percent.
Contrast Rating for High Ambient Light
The screen reflectance together with the screen brightness determine how easy it is to see the screen under high ambient lighting. We have defined a DisplayMate contrast rating for high ambient light (CRHAL) that is an excellent visual indicator of how screens look under high ambient light. This article has screen shots of 9 displays from 0 lux up to 40,000 lux ambient lighting - watch how they each degrade as the ambient lighting increases. The iPhone 4 has a CRHAL of 77. The current record holder is the Nokia Lumia 900 with a CRHAL of 90.
1st Tier Smartphone Goal and iPhone 5 Best Guess: Contrast rating for high ambient light over 90.
The Color Gamut is the range of colors that a display can produce. If you want to see accurate colors in photos, videos, and all standard consumer content the display needs to match the standard color gamut that was used to produce the content, which is called sRGB / Rec.709. Most mobile LCD displays produce around 60 percent of the standard color gamut in order to maximize screen brightness and battery running time. The iPhone 4 has a color gamut of 64 percent of the standard, which produces somewhat subdued colors. The new iPad 3 has a virtually perfect 99 percent of the standard, so we expect the iPhone 5 to follow suite. This figure shows the color gamuts for the iPhone 4, iPad 2, new iPad 3, and sRGB / Rec.709 standard. A widely held and exploited misconception is that the bigger the color gamut the better - but it isn't... A display with a larger than 100 percent color gamut cannot show colors that are not in the original content - it just exaggerates and distorts the colors.
1st Tier Smartphone Goal and iPhone 5 Best Guess: 100 percent of the sRGB / Rec.709 color gamut standard - not larger!
This article has been republished with permission from DisplayMate.com.
About the Author
Dr. Raymond Soneira is President of DisplayMate Technologies Corporation of Amherst, New Hampshire, which produces video calibration, evaluation, and diagnostic products for consumers, technicians, and manufacturers. See www.displaymate.com. He is a research scientist with a career that spans physics, computer science, and television system design. Dr. Soneira obtained his Ph.D. in Theoretical Physics from Princeton University, spent 5 years as a Long-Term Member of the world famous Institute for Advanced Study in Princeton, another 5 years as a Principal Investigator in the Computer Systems Research Laboratory at AT&T Bell Laboratories, and has also designed, tested, and installed color television broadcast equipment for the CBS Television Network Engineering and Development Department. He has authored over 35 research articles in scientific journals in physics and computer science, including Scientific American. If you have any comments or questions about the article, you can contact him at firstname.lastname@example.org.
About DisplayMate Technologies
DisplayMate Technologies specializes in advanced mathematical display technology optimizations and precision analytical scientific display diagnostics and calibrations to deliver outstanding image and picture quality and accuracy – while increasing the effective visual Contrast Ratio of the display and producing a higher calibrated brightness than is achievable with traditional calibration methods. This also decreases display power requirements and increases the battery run time in mobile displays. This article is a lite version of our intensive scientific analysis of smartphone and mobile displays – before the benefits of our advanced mathematical DisplayMate Display Optimization Technology, which can correct or improve many of the deficiencies – including higher calibrated brightness, power efficiency, effective screen contrast, picture quality and color and gray scale accuracy under both bright and dim ambient light, and much more. Our advanced scientific optimizations can make lower cost panels look as good or better than more expensive higher performance displays. For more information on our technology see the Summary description of our Adaptive Variable Metric Display Optimizer AVDO. If you are a display or product manufacturer and want our expertise and technology to turn your display into a spectacular one to surpass your competition then Contact DisplayMate Technologies to learn more.