Not all shades for safety lenses are created equally. You need to have the right lens shading for your specific application. For example, if you have eye sensitivity, work with lasers or are indoors and outdoors throughout the day, you will want to select the best types of shading for your needs.
You may want to use photochromatic, tinted or polarized lenses. Photochromic lenses will lighten and darken depending on the availability of ultraviolet light. A colored tint will permanently tint the lenses of your glasses. And polarized lenses will reduce glare through special polarized filters and also provide 100% UV protection.
To help you select the right lens shading for your application, below are the government guidelines for the appropriate shade numbers for various operations.
Filter Lenses for Protection Against Radiant Energy