The Tiffen 138mm UV 15 Filter is a general use, clear filter that helps to absorb ultraviolet light and reduce the bluish cast of daylight. This filter is especially useful when photographing at high altitudes or around bodies of water. No additional coloration or contrast is provided, allowing you to pair this filter with others. This filter attenuates approximately 81% of UV radiation, slightly less than a UV 16 filter.
The UV filter is also useful as a general protective filter to leave on lenses at all times. Filters help to reduce dust and moisture from reaching your lens element and provide additional protection in case of drops or situations where scratching could occur.
Tiffen filters are made using ColorCore technology; a process that involves laminating the filter substrate between 2 pieces of optical glass, grinding flat to a tolerance of 1/10,000th of an inch, then mounting to precision metal rings.