Visible Light Transmission (VLT) in Sunglasses

Sunglasses come in many styles and with various lens features. However, one of the most important factors to consider is visible light transmission (VLT). This refers to the amount of visible light that filters through the lenses to reach your eyes.  

Visible light transmission in sunglasses is expressed as a percentage. Dark-tinted lenses have a lower VLT percentage, meaning less light gets through them. Lighter lenses have a higher VLT percentage because they let more light reach your eyes.  

Understanding light transmission in sunglasses can be helpful when purchasing your next pair, whether you need them for deep-sea fishing, jungle trekking or everyday wear. VLT impacts how your sunglasses perform in various light conditions, playing a key role in your comfort and visibility on every adventure. 

Read on to learn more about VLT in sunglasses, how it’s categorized and which lens tints are best for different environments. 

Visible light transmission in sunglasses is grouped into specific categories according to the ISO 8980-3 standard set by the International Organization for Standardization (ISO). These categories are: 

Category 4 (S4): 3% to 8% VLT 

Sunglass lenses in this category have a very dark tint and allow a very small amount of light to reach the eyes. They’re designed for extremely bright conditions, such as mountaintop expeditions or bright, reflective snow. These lenses are too dark for driving or everyday use.  

Category 3 (S3): 8% to 18% VLT 

Category 3 sunglass lenses have a dark tint that makes them perfect for sunny days, whether you’re on the beach, on a boat or driving around town. Since they offer an ideal mix of light transmission and visibility, they’re also great for everyday use. Most Costa sunglass lenses fall into this category, delivering top performance for those long days in the sun. (See more on this below.) 

Category 2 (S2): 18% to 43% VLT 

Featuring a medium lens tint, sunglass lenses in the S2 category work best on overcast days or in moderate to low-light conditions. They’re great for fishing at sunrise or sunset because they provide visual clarity without blocking too much light. 

Category 1 (S1): 43% to 80% VLT 

Sunglasses in category 1 are ideal for low-light situations, such as dawn, dusk or heavily overcast days. These lenses have a light tint that allows more light to reach your eyes so you can see clearly when sunlight is limited. 

Category 0 (S0): 80% to 100% VLT 

Category 0 lenses are very lightly tinted or clear, letting in the most amount of light. They’re often used for eyeglasses, fashion purposes or activities like driving at night.

Costa is known for its innovative approach to lens technology, crafting cutting-edge shades for challenging conditions on the water and on land. Featuring the latest in polarization technology, our 580 lenses are built to reduce glare, enhance visual clarity and boost contrast in even the toughest environments.  

Costa 580 lenses strike the perfect balance between light transmission and polarization, offering superior optical clarity and glare reduction in various conditions.  

Costa lens tints and their VLT percentages include: 

• Blue mirror – 10% 
• Green mirror – 10% 
• Gray silver mirror – 10% 
• Copper silver mirror – 12% 
• Gray – 12% 
• Copper – 12% 
• Gold mirror – 15% 
• Rose gradient – 15% 
• Gray gradient – 15% 
• Sunrise silver mirror – 25% (Note: This tint is not suitable for driving) 

When selecting the ideal VLT for your sunglasses, it’s important to match the level of visible light transmission with the conditions you’ll be facing. For instance, consider whether your outdoor adventures will involve:  

• Bright conditions or deep water fishing trips – Opt for lenses with 10% VLT when tackling these environments. 

• Variable light conditions or shallow water activities – Lenses with 12% VLT can offer the best visual experience in these dynamic conditions. 

• Variable light conditions and everyday activities – Lenses with 15% VLT are perfect in varying light and for daily wear. 

• Low light or cloudy conditions – For these situations, lenses with 25% VLT are best for maintaining visibility. 

Costa sunglasses are built for outdoor enthusiasts. From fishing and water sports to shore excursions and beyond, these shades withstand the elements, allowing you to focus on the action without worrying about your eyewear. Explore our collections today and gear up for your next big adventure. 

• International standard (ISO 8980-3). International Standard Organization. June 2022. 

• What are polarized lenses for? EyeSmart. American Academy of Ophthalmology. June 2024. 

• Tips for choosing the best sunglasses. EyeSmart. American Academy of Ophthalmology. May 2024.