What Is “VLT” And Why Is It Important?

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When it comes to choosing sunglasses, we typically consider the frame, style, color, and tint, but we often forget to consider the lighting conditions we’ll be using them in. That’s where the term “VLT” comes in. But what exactly does it mean, and how do you know which VLT category to choose?

“VLT” refers to visible light transmission. It’s a measure of the amount of light that enters your eyes through the lenses on sunglasses. VLT is expressed as a percentage, and it’s divided into 5 categories, with category 4 indicating the darkest lenses and category 0 indicating the lightest. 

A higher VLT percentage means that more light will pass through the lens, while a lower VLT percentage means less amount of light will pass through. But which one is right for you? Let’s take a closer look at how VLT works and what each category is best used for.

What Does “VLT” Mean in Sunglasses?

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VLT, or visible light transmission, refers to the amount of light that enters your eyes via the lenses. It’s measured as a percentage indicating the lens’ darkness.

A number of factors affect the VLT, including the thickness and color of the lenses, the coatings on them, and what they’re made of. The lower the percentage of VLT, the darker the lens is going to be. 

What Are the Different Categories of VLT?

VLT percentages are divided into categories ranging from 4 (darkest) to 0 (lightest). Snow goggles might be represented by S4 to S0 (where S stands for snow).

Let’s take a closer look at these categories:

Category 4

The VLT in this category ranges from 3% to 10%, which means lenses that have this tint density are ideal for very, very bright conditions. For that reason, however, this category is not commonly found.

Since this tint level drastically reduces light transmission, category 4 lenses — like this pair of super dark sunglasses (on Amazon) — aren’t safe to use while driving or operating other vehicles. Instead, this VLT range is typically used in shop welding and high-altitude mountaineering. 

Category 3

In this category, the VLT ranges from 10% to 18%. Such tints (typically copper or gray) are usually used in everyday sunglasses. This VLT’s lower range is normally combined with a mirror coating and used for activities in the snow or water as well as for driving.

Goggles or sunglasses with this VLT range are most suitable for bright and sunny to slightly cloudy conditions. This stylish pair from Tom Ford (on Amazon) is an example of category 3 glasses.

Category 2 

This VLT range varies from 18% to 43% and is typically used for low-to-medium light conditions. The tint is meant for various activities and an average amount of sunlight. If you’re not light-sensitive, this range could also be a good option for everyday use.

Category 1

Category 1 VLT ranges from 43% to 80% and is suitable for low-light or dusk conditions. It’s particularly great for cloudy days.

The colors used are typically rose, amber, and yellow and are selected because of their high color contrast. Category 1 glasses — like this pair (on Amazon) — are ideal for activities like golf, cycling, and shooting. 

Category 0 

And finally, in category 0, the VLT ranges from 80% to 100%, which means there’s hardly any tint (some clear lenses can even have VLT that’s somewhere around 80%). Glasses with this VLT are typically used for safety, fashion, and night activities like cycling and snowboarding.

Variable VLTs

In addition to the five categories described above, there’s something called variable VLTs.

When light conditions change throughout the day, your best bet is photo-chromatic lenses that automatically go from a clear tint to a darker tint depending on your environment’s UV density. Such lenses are available in various options ranging from 15% to 50% VLT and work well in nearly all conditions. 

What Is Each VLT Category Best for?

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With five different categories to choose from, it can be tough to determine which lenses are best for which activity. Here’s an overview of the categories and what they can be used for:

  • Category 4 (3-8%): These lenses feature a very dark tint and work well in exceptionally bright light conditions, making them great for summer skiing and riding, and high-altitude glacier skiing in very sunny conditions. 
  • Category 3 (8-18%): These lenses also have a dark tint and are designed to work in bright light conditions, making them suitable for spring skiing and riding under sunny conditions. 
  • Category 2 (18-43%): Such lenses feature a medium tint and work well in all light conditions, making them great for all-purpose use (cloudy or clear and even variable sun). This is the most common VLT% range.
  • Category 1 (43-80%): These lenses feature a light tint and are great for overcast and dark days, blizzards, and stormy days. They’re also great for use in artificial light and are a good option for night riding or skiing. 
  • Category 0 (80-100%): This category essentially includes clear lenses with a barely-there tint. Such lenses are suitable for night riding or skiing.   

Are Lower VLTs More Expensive?

The price of the VLT depends on the brand as well as the model, so you’ll find a wide variety of prices out there. The category doesn’t necessarily dictate the price.

Which Category Should You Buy?

The VLT percentage plays a big role in how and when you can use your glasses, but when it comes to making a purchase, it all depends on your personal preference and how comfortable your eyes are in certain light conditions.

Nonetheless, there are some things you should keep in mind when making a purchase:

Category 2 or 3

A category 2 or 3 lens is usually a good option for everyday tasks, such as taking a stroll in the afternoon or driving when it’s sunny. Most general-use sunglasses feature a category 2 or 3 lens.

If you opt for a lens with less than 43% VLT, you’ll probably face a lot of problems on exceptionally bright days. In fact, you’ll most likely end up frowning or squinting, which can give you a headache over time.

Some fashion sunglasses feature lenses with a light tint, so make sure you first test how they perform under bright, sunny conditions before buying them.

Category 4 

Lenses with less than 8% VLT tend to be overly dark and can hinder your vision, particularly on a very sunny day. Category 4 lenses are also illegal for driving (at least in some places). They’re too dark to operate any vehicle safely since they can diminish indications from other vehicles and the light from traffic lights. So, if you really want a dark lens for the road, you shouldn’t go beyond category 3.

In general, category 4 lenses are used in situations with extreme exposure. For instance, mountaineering sunglasses sometimes feature side shields and 5% VLT lenses to reduce the risk of snow blindness.

So, if your sunglasses appear a bit too dark, make sure you check the VLT% to ensure you don’t break any rules.

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