Why is a clear lens advantageous in front of a filtered welding lens?

A clear lens is advantageous in front of a filtered welding lens primarily because it shields the filter lens from heat and sparks. During welding, there is a significant amount of heat generated, along with sparks and spatter that can occur from the welding process.

Having a clear lens acts as a protective barrier that absorbs much of the physical damage that can come from these sparks, thereby prolonging the life of the more expensive filtered lens underneath. This protective feature is crucial, as it helps maintain the integrity and effectiveness of the filter lens, ensuring that it can perform its function of protecting the welder's eyes against harmful radiation and brightness from the weld.

While enhancing visibility, preventing scratches, and reducing eye fatigue are also valid considerations when discussing welding lenses, the primary function of the clear lens in this context is its role in physical protection against the numerous hazards present during welding.