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My keyboard backlight is fairly dim. You can definitely see a bit of light through the keys, so it's functional, but it's uniformly more dim than it was when I first bought it and definitely more dim than my 13" 2011 MBP keyboard backlight. Any ideas?

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Is it at maximum brightness? And not auto dimming due to the envrionment. – MrDaniel Mar 7 '12 at 11:49
Yes, maximum brightness was used. – nick_name Mar 7 '12 at 18:48

White LEDs, as used in the keyboard backlights in apple laptops, do dim over time.

White LEDs use a blue LED, and an phosphor which is excited by the blue light, and re-radiates the energy in the orange-yellow spectrum. Unfortunately the phosphor does decay over time, reducing the efficiency of the LEDs.

However, the lifetime of modern LEDs is typically something in the range of ~50,000-100,000 hours to 50% brightness, so it's likely that there is some other mechanism in play for your situation. There are a number of external factors that can effect LED brightness, from poor-quality phosphors to overdriving of the LED die.

Can you estimate the brightness difference? If it's only a few percent different, it may just be normal aging, or lot-to-lot LED variance.

Anyways, if it bothers you, it may be covered under the apple-care warranty. It might be useful to take it to an apple-store and have them look it over.

Here is an interesting white-paper on LED life expectancy and ageing effects.

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