Overview
ISO 12312-2:2015 - "Eye and face protection - Sunglasses and related eyewear - Part 2: Filters for direct observation of the sun" specifies safety, optical and mechanical requirements for afocal (plano power) solar filters designed for direct observation of the sun (for example, solar eclipse viewing). It defines performance tests, labelling and user information to ensure filters block harmful solar radiation while allowing safe viewing.
Key topics and technical requirements
- Transmittance (optical density): Specifies very low luminous transmittance limits for solar filters (see Table 1 in the standard). Maximum and minimum luminous transmittance values, limits for solar UVA/UVB and infrared transmittance, and an allowable measurement uncertainty (≤ 25% of the measured value) are provided.
- Uniformity: Relative luminous transmittance variation between any two points shall not exceed 10% within a 40 mm diameter circle around the filter centre (or to the filter edge minus a 5 mm marginal zone).
- Material and surface quality: Filters must be free from vision‑impairing defects (bubbles, scratches, inclusions, undulations). Metal-coated filters may have no more than one pinhole ≤ 200 µm within any 5 mm circular zone.
- Mounting and dimensions: Filters may be mounted handheld or in spectacle form. Assemblies must stay secure in normal handling and meet minimum overall dimensions: at least 115 mm width and 35 mm depth in the facial plane. Nose cut‑outs and separate eye filters are allowed within specified limits.
- User safety and labelling: Packaging and filters must include manufacturer details, instructions for safe use, strong warnings about permanent eye injury from improper viewing, guidance on damaged filters, storage/cleaning advice and obsolescence information. Annexes include a user guide and practical advice for eclipse viewing.
Applications and who uses this standard
- Manufacturers of solar eclipse viewers, solar filters, spectacle‑shaped filters, handheld viewers - for design, production and conformity.
- Test laboratories performing optical transmittance, uniformity and material quality testing per ISO 12311:2013 references.
- Retailers, event organizers, educators and astronomy clubs seeking assurance their viewing products meet international safety criteria.
- Regulatory bodies and procurement teams specifying safe products for public eclipse events.
Keywords: ISO 12312-2:2015, solar eclipse viewing, filters for direct observation of the sun, solar filters, transmittance, eye protection, solar eyewear, safety standards.
Related standards
- ISO 12312-1 - Sunglasses for general use
- ISO 12311:2013 - Test methods for sunglasses and related eyewear (referenced for transmittance measurement)
- ISO 4007 - Vocabulary for eye and face protection
- ISO 16321 (welding filters) - discussed in Annex A as comparable for unaided solar viewing in specific scale categories
For safe solar observation always use products conforming to ISO 12312-2:2015 and follow the labelling and usage guidance included in the standard.