Do you know what do the categories 1, 2, 3 and 4 on the hangtags represent?
This is very important feature of sunglasses. But most people have no idea about what they mean.
They refer to transmittance ratio (transmission coefficient): the transmittance or penetration rate of visible light. For example, the transmission ratio of sunglass lenses is 40%, which means that only 40% of visible light can pass through the lenses and enter the eyes.
Category 1: light-colored sunglasses; transmission ratio 43%-80%, the lightest color, shade and reduce the amount of light transmission at least, mostly used in fashion accessories mirror
Category 2 light-colored sun shades; transmission ratio 18%-43%, slightly lighter color, cloudy days or cloudy with
Category 3: sun shades; transmission ratio 8%-18%, most sunglasses belong to this level, suitable for beach, hiking and other outdoor activities
Category 4: special-purpose sunglasses; transmission ratio 3%-8%, suitable for skiing, desert, welding and other environmental use.
According to the driving requirements, the transmission ratio must be greater than 8%, so the fourth category of sunglasses are not suitable for driving.
Some sunglasses will cause recognition difficulties of traffic signal, thus causing some traffic accidents due to the transmission ratio failing to meet the requirements.
