Tuesday, October 2, 2012

The Apple Camera

"Purple Haze was in my brain,
lately things don't seem the same,
actin' funny but I don't know why
'scuse me while I kiss the sky.:

Purple Haze Lyrics by Jimi Hendrix

In addition to the Map issue, the Apple 5 seems to have an issue with the camera. Specifically, it is generating a purple flare around bright objects. One of the features that was changed with the iPhone 5 camera was the addition of a sapphire lens. Sapphire is harder than glass but like most transparent things harder than glass, it also has a higher index of refraction. The higher index means that an uncoated lens will have higher surface reflections and higher scattering, particularly for blueish light. Even in the lens of your own eye, blue light tends to scatter more than red which is why many sun-glass brands switched from green to red or orange and why black and white photos tend to be clearer with a 25A red filter on the camera.

Apple may have had the lens coated and the coating gets worn off or was not properly done. The camera being digital, it should be possible to implement a software fix. The sapphire lens was probably implemented in response to a customer issue and is likely to to stay. The image above is a Hendrix album cover and obviously not taken with an iPhone 5 camera.


  1. With a roughly spherical shape, it was common for the face of CRTs to get scratched during the manufacturing process. My company, produced the glass and was asked by RCA if we could provide a coating that would reduce theses scratches. Every coating that we looked at had a higher index of refraction and resulted in a TV tube surface that was even more reflective than plain glass. The reflections were judged to be unacceptable and no further investigations followed.

    In the per-Gorilla Glass environment, sapphire was commonly used to cover watch faces and instrument gauges in industrial environments. These days, sapphire demand is up due to it being the preferred substrate to build LEDs on.

    Sapphire being a crystal rather than a glass, it has an orderly molecular structure. The secondary reflections in the images provided by Gizmodo may be due to that structure.

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