BS 2724:1987

Foreword
Committees responsible
Specification
1. Scope
2. Definitions and explanation of terms
3. Transmittance
4. Refraction properties
5. Quality of filter material and surface
6. Stability
7. Frames
8. Mechanical strength of break resistant, robust and
     impact resistant sunglasses
9. Information and labelling
Appendices
A. Recommendations for the use of sun glare eye
     protection
B. Methods for determination of transmittance for all
     sun glare filters, the axis of polarization of
     polarized filters and fatigue of photochromic
     filters
C. Methods for determination of refractive, astigmatic
     and prismatic powers
D. Methods for determination of quality of material
     and surface
E. Methods for determination of filter material
     stability and mechanical strength
Tables
1. Shade numbers and transmittance values of filters
2. Permissible refraction tolerances of filters
3. Refraction requirements for mounted filters
4. Classification and uses of sunglasses
5. Factors required for determining the relative
     visual attenuation coefficients and luminous
     transmittance
6. Spectral irradiance for the infra-red spectral range
Figures
1. Spectral transmittance of heat absorbing filter
2. Outline of apparatus used for the determination
     of the axis of polarization
3. Target for use when determining the refractive
     properties of filters
4. Outline of apparatus used to assess the surface
     quality of filters
5. Outlines of apparatus used for the measurement of
     scattered light in filters
6. Illustration of the method used for assessing
     strength of frame and bridge of sunglasses

Requirements for both unmounted filters and those mounted in frames. Photochromic and gradient filters are also specified.