Ion-X Glass vs. Sapphire Crystal: Apple Watch Sport brighter, easier to read than Apple Watch

“Is there a visual difference between a watch that uses sapphire versus glass?” Dr. Raymond M. Soneira reports for DisplayMate. “If you were to hold up two identical watches side-by-side, the one with a glass crystal would be about 20 percent brighter than the one with sapphire (due to fundamental principles of optics that reduce its light transmission), so it appears somewhat darker and duller, particularly because the light has to pass through the crystal twice.”

“Minimizing screen reflections is especially important for displays, and sapphire has almost double (191%) the Reflectance of glass,” Soneira reports. “If you are watching a display in total darkness then the screen reflectance doesn’t matter, but it has a surprisingly large effect on every display, even in subdued indoor ambient lighting, and it makes an enormous difference outdoors.”

“We’ll show below how large and how important the reflectance effect is by comparing the display on an Apple Watch that has a Sapphire Crystal to an identical display on an Apple Watch Sport that has Ion-X Glass,” Soneira reports. “The Apple Watch models are perfect for this comparison because they are identical except for their sapphire and glass covers. But they look and perform identically only in the dark…”

Photo of the Apple Watches in 2,000 lux Uniform Ambient Light

Apple Watch Sport with Ion-X glass (left), Apple Watch with sapphire crystal (right) (Source: DisplayMate)
Apple Watch Sport with Ion-X glass (left), Apple Watch with sapphire crystal (right) (Source: DisplayMate)

Much more in the full article – recommended – here.

MacDailyNews Take: We’re loving our Apple Watch Sport models and, after over nine weeks of wearing them 16-18 hours per day, including during sports (running, skating, soccer), there’s not a scratch on either the Ion-X Glass display or the 7000 Series aluminum watch case!


      1. But this is a jewellery crystal, so, naturally, it sparkles/reflects twice more light than glass. This is whole point of emerald, ruby and sapphire, but bad if you use those crystals as display cover.

        With Apple Watch things are additionally complicated because its OLED screen has relatively low maximum brightness due to limitation of OLED and for the purpose of energy saving.

        My guess is that in few years actual contrast ratio under sun will significantly improve; but not now yet.

        1. No, you are wrong. Reflectivity is what you are talking about when what a sapphire does is let more light in and then reflect it back . . . it has more “sparkle” than glass. That’s called refractivity, not reflectivity. Surface reflection can be controlled by adding coatings.

          This whole article is just wrong. I just put my Apple Watch up next to my girlfriend’s Apple Watch Sport. . . and my Apple Watch with a sapphire crystal was brighter and clearer than her Apple Watch Sport with its Ion-X glass. It certainly was not anywhere near as obvious as the photo above, but there was a slight difference with the Apple Watch Sport having a slightly lower brightness, clarity, and quality than the Apple Watch. I suspect a lot of it might be in the brightness setting of the respective watches which would have nothing to do with the crystal installed on the watch.

        2. Refractivity defines angles, not the brightness of reflections, so I am right. (You can shape a glass in certain forms that would provide maximum number of reflections before the light will come back to viewer, but this will still look like a glass, not a true gem due to low reflectivity.)

  1. Something to look at closely under normal light the next time I’m at the Apple store. Holding it in your own hands is always the best way to make a decision.

    1. I got my Italian black rubber Bumper cover from Rome this week before sustaining any scratches on my SG WATCH SPORT. This $35 cover looks fantastic and really gives maximum protection to all but the glass. And Amazon sells protective covers for the glass for only $6.95.
      ArmorSuit MilitaryShield – Apple Watch 42mm Screen Protector.

  2. Gee, I hope MacDailyNews has written permission to reprint the bits of the DisplayMate article. At the top of the article, in red text, it says,

    “Copyright © 1990-2015 by DisplayMate Technologies Corporation. All Rights Reserved.
    This article, or any part thereof, may not be copied, reproduced, mirrored, distributed or incorporated into any other work without the prior written permission of DisplayMate Technologies Corporation”

  3. Nothing is free and virtually every decision reflects a compromise. Sapphire is extremely scratch resistant, but does not have the same transmissibility as the glass option.

    I did not understand the statement that the sapphire version “…appears somewhat darker and duller, particularly because the light has to pass through the crystal twice.” The Apple Watch OLED display emits light that passes through the crystal once on its way to your eyes. If Dr. Soneira meant that the light from the OLED display passes through two surfaces of the crystal, then that would be accurate.

  4. Just got my apple watch 2 days ago. Space grey sport. Very intriguing. Beautifully done like all of apples products. I find my self cautious wearing it, unlike when wearing my tag. I realize it isn’t gonna handle the abuse. At this point I couldn’t see spending $300 more. I’m not crazy about the sport band. On and off isn’t that quick and easy. I do see allot of aftermarket bands already. Maybe I’ll go that route.

    1. Congrats. I felt like you at first. But it does take a few weeks to get used to it. Once you figure out exactly which hole is right for a snug but not too tight fit, taking it off and on will be a lot easier than it is at first. I even went so far as to buy blue leather loop band the week they reached the Apple stores. But that turned out to be worse than the black WATCH SPORT band – silver hole for the leather loop is a major distraction. Now I love the black band. So give it some time to get used to it before deciding against it.

  5. Don’t get too cocky. I let my wife wear my brand new Space Gray sport and at the end of her first full day of wearing it, while washing it off I discovered that it had a pretty deep 1/2″ scratch aright across the front of the glass. So, I guess she’s pretty hard on them. She was gardening and potting plants and stuff, but doesn’t really remember how it happened. She loves the watch though, so I’m going to get her one. But, I’ll make her’s the stainless steel, sapphire crystal one!

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