Overview
EN ISO 12312-2:2015 (ISO 12312-2:2015) is the CEN-endorsed international standard that specifies requirements and test methods for afocal (plano power) filters intended for direct observation of the sun, for example solar eclipse viewing. It defines optical, material and marking requirements for solar filters and includes informative guidance on safe use (Annex A and a user’s guide for solar eclipse eye safety in Annex B). This standard does not apply to general‑use sunglasses, sports eye protectors, prescription sunglass lenses, or eyewear for artificial light sources.
Key topics and technical requirements
- Transmittance limits: The standard sets strict limits for luminous transmittance and spectral transmittance across UV (UVA/UVB) and infrared bands to ensure eye safety during direct solar observation.
- Measurement methods: Spectral transmittance for high optical‑density filters is measured using appropriate instrumentation (for example dual‑beam spectrophotometers with comparison beam attenuators). The standard specifies acceptable measurement uncertainty.
- Uniformity: Luminous transmittance must be uniform - the relative difference between any two points within the specified central area is limited (measurement circle and tolerance defined in the standard).
- Material and surface quality: Filters must be free from defects that could impair vision (bubbles, scratches, inclusions, pits, undulations) except within a defined marginal zone. Metal‑coated filters have a limited allowance for very small pinholes (maximum diameter and frequency defined).
- Mounting and dimensions: Requirements address mounting quality and dimensional criteria to ensure the filter can be used safely in holders or frames intended for solar observation.
- Labeling and information: Manufacturers must supply instructions and markings required for safe use; informative annexes provide user guidance for solar eclipse viewing.
Practical applications and users
This standard is intended for:
- Manufacturers and designers of solar filters and eclipse-viewing eyewear
- Test laboratories performing conformity and spectral transmittance testing
- Certification bodies and regulators assessing product safety
- Event organizers, retailers and buyers seeking compliant solar viewing products
- Safety officers and outreach educators producing guidance for public solar observation
EN ISO 12312-2:2015 helps ensure that products marketed for direct sun observation meet reproducible optical and safety criteria, reducing risk of retinal injury.
Related standards
- ISO 12312-1 - Sunglasses for general use (complements Part 2)
- ISO 12311:2013 - Test methods for sunglasses and related eyewear (normative reference)
- ISO 4007 - Vocabulary for eye and face protection
Keywords: EN ISO 12312-2:2015, ISO 12312-2:2015, solar filters, solar eclipse eyewear, direct observation of the sun, afocal eyewear, transmittance, UV protection, spectrophotometer, eye and face protection.
