So, what is visible light transmission?
You may have noticed on every single one of our sunglass lens listings we have a category number listed. You might be asking yourself, what does this mean? Well, you’ve come to the right place.
The category number refers to the visible light transmission (or VLT). This simply refers to what percentage of ambient light is allowed to pass through your sunglass lenses (aka how dark the sunglass lenses are). For instance, our Clear lenses have a VLT of 100%. This means that 100% of the visible light passes through them (because they’re clear). The darker your lenses get, the smaller that percentage becomes (and the higher category they are included in) because they are letting in less light. This number does not refer to how protective the lenses are, just how dark they are.
VLT is affected both by lens color and the coatings that are put on top of the lenses. You can have the same grey base lens, but if you add a mirror to one of them, it will change the way the lens allows light to pass through, and thus affects the darkness of the lens. But, you don’t have to worry about figuring it out on your own – we list the category number of every one of our sunglass lenses, remember?
There are 5 categories of VLT that your sunglasses can fall under. You may see the cut offs vary from source to source, but the categories are generally accepted. Those categories are as follows:
Category 0: 80 – 100%
Category 1: 46 – 79 %
Category 2: 18 – 45 %
Category 3: 10 – 17 %
Category 4: 3 – 9 %
Now, let me break it down for you.
Category 0: 80 – 100%
Very Low Light/Night
As I mentioned before, our clear lenses would fit into this category. Our clear lenses let in 100% of the light around you, making them ideal for night time when you don’t need any darkening power. Our Gaming lens (yellow tinted with our Ion backside coating) also fits in here. Obviously, you can wear these lenses outside and at other times during the day, you’ll just have to squint a little. Your eyes will still protected though – all of our lenses, even our clear lenses, are 100% UV protected!
Category 1: 46 – 79%
Lenses in this category are great for lower-light conditions or basically anytime you want lenses but aren’t out in the blazing sun. Our Photochromic (Darkening) lenses start out in this category and darken as you spend time outside.
Category 2: 18 – 45%
Lenses that fall into this category are great for everyday use – errands, driving, looking cool – you name it. Sunglasses in this category darken your view enough to increase eye comfort but are still bright enough to be able to see exactly what you are doing. All of our fashion gradients fall into this category, they are a perfect choice for a day out on the town. Our yellow polarized lenses also fall into this category. Yellow polarized increases color contrast and can help your view drastically on hazy days.
Category 3: 10 – 17%
A majority of Fuse Lenses fall into this category. Lenses in this range are great for sports, going to the beach, fishing, and other outdoor activities. These lenses cut through bright light and but are still perfectly suitable for driving. Just a few examples are our Cosmic mirror, Cascade mirror, Nova mirror, brown tinted lenses, and more.
Category 4: 3 – 9%
Very Strong Light
Lenses from this category, you won’t find in retail stores often. They are commonly specialized lenses for activities that require more darkening and glare reduction then most people need. We sometimes have one or two lenses that creep into this category – just know that the darkest we can (legally) sell is 8% VLT, so don’t be crazy. We want you to be comfortable, but still be able to see.
So, there you have it. VLT categories all broken down! If this is too much and you just want to know what lens is the best for fishing, driving on cloudy days, or what our darkest lens is – just ask us! Email us your questions anytime at firstname.lastname@example.org and we’d be happy to help you out.