UV Index

UV Index is a standardized 0-15+ scale measuring ultraviolet radiation intensity at Earth's surface, providing photographers with insights into both atmospheric clarity and practical concerns for skin protection and equipment exposure during extended outdoor shoots. Unlike visible light radiation, UV measures the invisible short-wavelength component that doesn't contribute to exposure but reveals atmospheric conditions and affects safety.

Low UV Index of 0-2 occurs under overcast skies, during twilight hours, or in winter at high latitudes, indicating conditions where cloud cover or low sun angles minimize UV penetration—though visible light photography remains perfectly viable. Moderate UV 3-5 suggests partly cloudy conditions or clear skies during morning and evening hours when sun angles reduce UV intensity despite adequate visible light for photography. High UV 6-7 indicates midday clear-sky conditions at mid-latitudes where strong direct sunlight creates both abundant photographic light and significant UV exposure requiring sun protection for photographers spending hours outdoors. Very high UV 8-10 occurs at high elevations, low latitudes, or during summer clear skies, revealing exceptional atmospheric transparency ideal for landscape clarity but demanding serious sun protection including sunscreen, long sleeves, and breaks in shade. Extreme UV 11+ occurs at high altitude in tropics or on reflective surfaces like snow and water, creating hazardous exposure requiring comprehensive protection during extended shoots.

For photographers, UV Index serves as atmospheric clarity proxy: high UV indicates clear skies, low haze, and excellent long-distance visibility perfect for mountain landscapes and telephoto work, while low UV often correlates with overcast, haze, or marine layer reducing distant clarity. UV also affects equipment: prolonged exposure to intense UV can fade camera strap colors, degrade rubber grips, and potentially affect sensor filters over years of use, though practical impact remains minimal for most photographers. Snow photography uniquely challenges UV exposure as snow reflects 80-90% of UV radiation, essentially doubling exposure and creating snow blindness risks plus increased skin burn danger requiring comprehensive protection. PhotoWeather displays UV Index to help photographers plan sun protection for extended shoots, correlate UV with atmospheric clarity for landscape planning, and anticipate exceptional clarity opportunities when UV peaks above typical values for the season and location. For astrophotography and ultra-clear landscape conditions, high UV during day often signals exceptional clarity continuing into night. For comfortable extended shooting without aggressive sun protection, prefer UV below 5. For maximum clarity and dramatic blue skies, embrace UV 7-10 with appropriate precautions.