When the testing card is exposed under the blue light directly, its color will change apparently. And we can judge the amount of the blue lights from the color. It can be said that the darker the color is, the more the blue lights are. When we shine the testing card through the lens, we can know the quality of the lens through the color change. If there no color change or just a slight color change can been seen, the lens can be said to be effective. On the other hand, the testing card changes in its color, it cannot filter the bad blue lights.
1.Put the lens on the testing area, and shine the testing card for 5 seconds.
2.One part of testing card becomes dark greatly, while the other part sheltered by the lens doesn’t change color.
3.Remove the lens and shine on the testing card, then it darkens, too.
Livho lens can block the harmful blue light.