Luminous transmittance variation is concerned with how consistently the auto-darkening function of the lens works. Our welding helmets in Variation Class 1 feature lenses where the shade of the filter darkens uniformly across the surface of the lens, with no dark or light areas in comparison to the lens as a whole. If you have any questions or need a product recommendation, do not hesitate to contact our customer support team on 020 7501 0594 or via our Contact Us page.