DisplayMate blue light

The media has given a fair amount of attention to the problem of blue light disrupting our normal circadian rhythm, making it more difficult for some people to fall asleep after reading portable displays or watching television. Apple has introduced a new Night Shift feature in its iOS 9.3 operating system. It is supposed to work by lowering the amount of blue light emitted by their mobile devices at night. But does it work?

For matters related to display technology, I turn to my friend and colleague Ray Soneira of DisplayMate. He is an “expert’s expert,” and does some of the most extensive and in-depth testing of displays in the industry. He just release a free report, “Watching Displays at Night,” which covers the blue light issue and some of the possible solutions, including Apple’s Night Shift. As cited by Ray, there is strong scientific evidence that blue light in the range of 460 to 490 nm wavelengths can indeed disrupt the production of melatonin, which is a hormone that the human body produces to help promote the onset of sleep.

Reducing the blue light output of a typical display results in proportionally more red and green light, which gives images a yellow tinge. As Ray shows in detail, the Apple Night Shift does reduce blue light output, but the bulk of the reduction happens outside the range that is accepted as the portion of the spectrum that causes the problem. In contrast, a television using the new “quantum dot” technology produces light within a much narrower range of wavelengths, and can produce a good image while emitting much less light in the problem range of the spectrum. In this case, you would not need to dim the blue portion of the display because it is already producing less of the problem wavelengths.

I encourage you to ready the whole report, as Ray explains why typical “blue blocker” sunglasses are not effective with this problem, and he makes a number of practical suggestions about how to minimize the effect of blue light on people who view a display in the evening before going to sleep. In many cases, simply switching to white text on a black background and dimming the display can be sufficient solutions.