ISO 12312-2 Requirements
A complete technical breakdown of the international standard for solar viewing filters. Understanding every requirement is essential—partial compliance is not compliance.
All Requirements Must Be Met
ISO 12312-2 is a complete standard. A product that meets only the transmittance requirements but fails labeling, uniformity, or packaging requirements does not comply with ISO 12312-2.
Some organizations have incorrectly listed products as "meeting ISO 12312-2" when they only met transmission requirements. This website requires verification of all requirements before a manufacturer appears on our approved list.
What is ISO 12312-2?
ISO 12312-2:2015, titled "Eye and face protection — Sunglasses and related eyewear — Part 2: Filters for direct observation of the Sun," is the international standard that defines safety requirements for solar viewing products such as eclipse glasses and handheld solar viewers.
The standard was adopted in 2015 by the International Organization for Standardization (ISO) and supersedes earlier national and regional standards. It applies worldwide and establishes the minimum requirements a solar viewer must meet to protect users' eyes during direct solar observation.
Scope of the Standard
ISO 12312-2 applies specifically to:
- Non-magnifying (1x power) solar viewing products
- Products intended to be handheld or worn like eyeglasses
- Filters for direct observation of the everyday Sun (photosphere)
ISO 12312-2 does not apply to solar filters meant for camera lenses, binoculars, or telescopes. However, filter material that meets ISO 12312-2 transmittance, uniformity, and quality requirements is generally suitable for use as an aperture filter for optical devices.
The Five Categories of Requirements
ISO 12312-2 establishes requirements in five distinct areas:
- Transmittance (§4.1.1) — How much light the filter allows through
- Uniformity (§4.1.2) — Consistency of optical density across the filter
- Material & Surface Quality (§4.2.1) — Freedom from defects
- Mounting (§4.3) — Physical construction requirements
- Labeling (§5) — Required markings and information
⚠️ Partial Compliance Is Not Compliance
A product must meet ALL five categories of requirements to be ISO 12312-2 compliant. Meeting transmittance requirements alone does not make a product compliant with the standard, regardless of what some organizations may claim.
Transmittance Requirements
Transmittance requirements define the maximum amount of light a solar filter may allow to pass through to the eye. These limits protect the retina from damage caused by visible light, ultraviolet radiation, and infrared radiation.
| Wavelength Range | Type | Maximum Transmittance | Equivalent Optical Density |
|---|---|---|---|
| 380nm – 780nm | Luminous (Visible Light) | ≤ 0.0032% | OD ≥ 4.5 |
| 250nm – 380nm | Ultraviolet (UV) | ≤ 0.0032% | OD ≥ 4.5 |
| 780nm – 1400nm | Infrared (IR) | ≤ 3% | OD ≥ 1.5 |
💡 Why This Matters
The Sun's surface brightness is approximately 1.6 billion candelas per square meter. Without adequate filtering, even brief exposure can cause solar retinopathy—permanent damage to the retina. These transmittance limits reduce the Sun's intensity to safe levels while still allowing a satisfying view.
Minimum Transmittance
The standard also specifies a minimum luminous transmittance of 0.00003% (OD 6.5). Filters darker than this may still be safe, but they may make the Sun too dim to observe comfortably.
Understanding the IR Limit
You may notice that the infrared limit (3%) is significantly higher than the visible and UV limits. This is because during unmagnified viewing, infrared radiation is less effective at causing retinal injury than visible or UV light. The technical basis for this is explained in the scientific literature referenced by ISO 12312-2.
✓ Compliance Checklist — Transmittance
- Luminous transmittance (380–780nm) between 0.00003% and 0.0032%
- UV transmittance (250–380nm) no greater than the measured luminous transmittance
- IR transmittance (780–1400nm) no greater than 3%
- Testing performed by an accredited laboratory using calibrated spectrophotometer
Uniformity of Transmittance
The uniformity requirement ensures that optical density is consistent across the entire filter surface. A filter with uneven density could have "hot spots" that allow dangerous amounts of light through in certain areas.
| Requirement | Specification |
|---|---|
| Uniformity of luminous transmittance | Within ±10% across the filter surface |
This means that if a filter has a measured luminous transmittance of 0.001% at one point, all other points on the filter must be between 0.0009% and 0.0011%.
💡 Why This Matters
Inconsistent optical density is a common problem with low-quality filters. A filter might pass transmittance testing at one measurement point while having dangerous variations elsewhere. The uniformity requirement ensures the entire viewing area is equally safe.
⚠️ Common Failure Mode
Cheap solar filter materials often exhibit significant uniformity problems. Testing at a single point may show acceptable transmittance, but multiple-point testing reveals variations that exceed the ±10% limit. This is why uniformity testing is essential.
Material & Surface Quality
Material and surface quality requirements ensure that filters are free from defects that could impair vision or safety. Physical defects can create pathways for unfiltered light to reach the eye.
Defect-Free Requirements
Filters must be free from:
- Bubbles — trapped air or gas in the filter material
- Scratches — surface damage that could affect optical properties
- Inclusions — foreign particles embedded in the material
- Dull spots — areas of reduced optical clarity
- Pitting — small holes or depressions in the surface
- Scouring — abrasion patterns from manufacturing
- Pocking — irregular surface marks
- Scaling — flaking or peeling of coatings
- Undulations — wavy distortions in the material
Pinhole Requirements
For metal-coated filter materials (common in eclipse glasses), the standard specifies:
| Requirement | Specification |
|---|---|
| Maximum pinholes per 5mm diameter zone | ≤ 1 pinhole |
| Maximum pinhole diameter | < 200μm |
💡 Why This Matters
Pinholes are tiny holes in the filter coating that allow unfiltered sunlight to pass through. Even a small pinhole can create a concentrated beam of light that reaches the retina. The standard limits both the number and size of acceptable pinholes.
✓ Compliance Checklist — Material Quality
- Visual inspection shows no bubbles, scratches, inclusions, or other listed defects
- Microscopic examination confirms pinhole requirements are met
- Surface coatings are intact with no scaling or peeling
- Filter material is optically clear without distortions
Mounting Requirements
Mounting requirements address the physical construction of solar viewers, ensuring they are safe to handle and use, and that filters remain securely in place during use.
Filter Security (§4.3.1)
Filters must be securely mounted so they cannot be dislodged by normal handling or gusts of wind. The filter must remain in place during all reasonably foreseeable conditions of use.
Size Requirements (§4.3.2)
Solar viewers must be large enough to cover both eyes of an adult user. For eclipse glasses with a nasal cutout, the cutout must fit a typical adult nose.
Material Safety (§4.3.3)
The filter and mounting must be free from:
- Roughness that could cause discomfort
- Sharp edges that could cause injury
- Projections that could harm the user
- Materials known to cause skin irritation
💡 Why This Matters
A filter that falls out during use leaves the user staring at the unfiltered Sun. Sharp edges or irritating materials may cause users to adjust the glasses frequently, increasing the risk of accidental exposure. These requirements ensure the product can be used safely throughout an eclipse viewing session.
Labeling Requirements
Labeling requirements ensure that solar viewers carry essential information for safe use and enable traceability back to the manufacturer. This section is frequently where non-compliant products fail—even when their filters meet transmittance requirements.
Required Information
The filter and/or its packaging must display the following information:
| Reference | Requirement | Details |
|---|---|---|
| §5(a) | Manufacturer Identification | Name and address of the manufacturer or responsible party |
| §5(b) | Instructions for Use | Clear instructions on how to safely observe the Sun or a solar eclipse |
| §5(c) | Eye Injury Warning | Warning that viewing the Sun without an appropriate filter can result in permanent eye injury |
| §5(d) | Damage Warning | Warning that damaged or separated filters should be discarded |
| §5(e) | Care Instructions | Advice on storage, cleaning, and maintenance as appropriate |
| §5(f) | Obsolescence Information | Obsolescence deadline or period, as appropriate* |
Modern solar filter materials do not degrade over time when properly stored. Research indicates that this requirement may be omitted in future revisions of the standard. However, until the standard is officially revised, products should include appropriate obsolescence information.
💡 Why Labeling Matters
Labeling requirements serve critical functions: they enable consumers to identify the manufacturer and verify authenticity, provide essential safety information for proper use, and create accountability. A product without proper labeling cannot be traced back to its source if problems arise—a major concern when dealing with potential counterfeit products.
⚠️ The Most Common Compliance Failure
Labeling is the requirement most frequently failed by products that otherwise have acceptable optical properties. Missing manufacturer information, inadequate warnings, or incomplete instructions are common issues. Some organizations have chosen to overlook labeling failures for products they consider "safe"—we do not. A product without proper labeling does not meet ISO 12312-2.
Language Requirement
All required information must be provided in the language(s) of the country where the product is sold. For products sold in the European Union, this typically means providing information in the official language(s) of each member state where the product is marketed.
✓ Compliance Checklist — Labeling
- Manufacturer name and physical address clearly displayed
- Complete usage instructions provided
- Eye injury warning present and prominently displayed
- Warning about damaged/separated filters included
- Storage and care instructions provided
- All text in appropriate language(s) for the market
Additional EU Requirements
Selling in the European Union?
Products sold in the European Union must meet additional requirements beyond ISO 12312-2. The EU classifies eclipse glasses as Personal Protective Equipment (PPE) Category 2, which requires third-party certification by an EU Notified Body.
This is significant: while some organizations were arguing in 2024 that ISO 12312-2 was "too strict," the EU moved in the opposite direction—adding additional layers of verification and accountability.
EN ISO 12312-2:2022
The European adoption of ISO 12312-2, incorporating the international standard into EU regulations.
PPE Category 2 Certification
Requires EU Type Examination by an authorized Notified Body before products can be sold in the EU.
Declaration of Conformity (DoC)
Manufacturer must issue a formal declaration that the product meets all applicable EU requirements.
CE Marking
Products must bear the CE mark with the Notified Body number (e.g., CE 0527) indicating third-party certification.
Understanding PPE Categories
The EU PPE Regulation (EU) 2016/425 classifies personal protective equipment into three categories based on the level of risk they protect against:
| Category | Risk Level | Certification Required | Examples |
|---|---|---|---|
| Category I | Minimal risk | Self-certification by manufacturer | Gardening gloves, sunglasses for general use |
| Category II | Intermediate risk | EU Type Examination by Notified Body | Eclipse glasses, safety glasses, hard hats |
| Category III | High/irreversible risk | EU Type Examination + ongoing production control | Respiratory protection, fall protection |
💡 Why Eclipse Glasses Are Category II
Eclipse glasses protect against risks that are neither minimal nor immediately life-threatening, but can cause serious, permanent harm—specifically, irreversible retinal damage. This intermediate classification requires independent third-party verification but does not require the ongoing production surveillance mandated for Category III equipment.
EU Type Examination Process
For PPE Category II products like eclipse glasses, the manufacturer must submit their product to an EU-authorized Notified Body for Type Examination. This process includes:
- Application Submission — Manufacturer submits technical documentation including product specifications, design drawings, test reports, and quality control procedures.
- Documentation Review — The Notified Body reviews all documentation for completeness and compliance with applicable standards (EN ISO 12312-2:2022).
- Product Testing — The Notified Body either conducts testing directly or reviews test reports from accredited laboratories to verify compliance with all requirements.
- Type Examination Certificate — If the product meets all requirements, the Notified Body issues an EU Type Examination Certificate valid for up to 5 years.
A Notified Body is an organization designated by an EU member state to assess conformity of products before they are placed on the market. Each Notified Body is assigned a four-digit identification number. For example, ECS GmbH (Germany) is Notified Body 0527, and TÜV Rheinland is 0197. The complete list of authorized Notified Bodies is maintained in the EU's NANDO database.
Declaration of Conformity (DoC) Requirements
The EU Declaration of Conformity is a formal document in which the manufacturer declares that their product meets all applicable EU requirements. This is a legal declaration—the manufacturer assumes full responsibility for the product's compliance.
Required Contents of a DoC
Under the PPE Regulation (EU) 2016/425, a valid Declaration of Conformity must include:
| Element | Requirement |
|---|---|
| PPE Model/Type | Clear identification of the product covered by the declaration |
| Manufacturer Information | Name and full address of the manufacturer |
| Authorized Representative | If applicable, name and address of the EU-based authorized representative |
| Declaration Statement | "This declaration of conformity is issued under the sole responsibility of the manufacturer" |
| Object of Declaration | Description of the PPE (may include image) |
| Applicable Standards | Reference to harmonized standards applied (e.g., EN ISO 12312-2:2022) |
| Notified Body Information | Name, number, and address of the Notified Body that performed the EU Type Examination |
| Certificate Reference | EU Type Examination Certificate number |
| Date and Signature | Place and date of issue, signature of authorized person with name and function |
⚠️ Common DoC Problems
Many products claiming EU compliance have Declarations of Conformity that are incomplete, reference non-existent certificates, or name Notified Bodies that did not actually certify the product. Always verify that the Notified Body number matches an authorized body and that the certificate number can be confirmed with that body.
CE Marking Requirements
Once a product has obtained EU Type Examination certification and the manufacturer has issued a Declaration of Conformity, the product must bear the CE marking before it can be sold in the EU.
CE Marking Format for PPE Category II
For eclipse glasses (PPE Category II), the CE marking must:
- Include the CE symbol in the correct proportions (minimum 5mm height)
- Be followed by the Notified Body's four-digit identification number
- Be visible, legible, and indelible on the product or its packaging
| Correct Format | Example | Meaning |
|---|---|---|
| CE + Notified Body Number | CE 0527 | Product certified by ECS GmbH (Notified Body 0527) |
| CE + Notified Body Number | CE 0197 | Product certified by TÜV Rheinland (Notified Body 0197) |
💡 Why the Number Matters
The four-digit Notified Body number is not optional decoration—it indicates which organization has verified the product's compliance. A CE mark without this number on PPE Category II products is non-compliant. The number allows anyone to look up the certifying body and verify the certification.
Manufacturer Obligations
EU regulations place ongoing obligations on manufacturers beyond initial certification:
- Technical Documentation — Maintain complete technical documentation for 10 years after the product is placed on the market
- Production Conformity — Ensure all manufactured products conform to the certified type (not just the samples submitted for testing)
- Traceability — Ensure products can be traced through the supply chain via batch numbers or serial identification
- Market Surveillance Cooperation — Cooperate with authorities if compliance issues are identified
- Non-Conformity Procedures — Take corrective action and notify authorities if products are found to be non-compliant
✓ EU Compliance Checklist
- Product tested to EN ISO 12312-2:2022 by accredited laboratory
- EU Type Examination Certificate issued by authorized Notified Body
- Declaration of Conformity contains all required elements
- CE marking includes Notified Body identification number
- Technical documentation maintained and available
- Product labeling meets EU language requirements for target markets
The PPE Category 2 and Declaration of Conformity requirements described above apply specifically to EU member states. Products sold in the United Kingdom (post-Brexit) may require UKCA marking and certification by a UK-approved body, depending on current regulations. Iceland, Norway, and Liechtenstein (EEA members) generally accept CE-marked products. Switzerland has bilateral agreements that may affect requirements. Always verify current regulations for your specific target market.
Testing & Certification
ISO creates standards, but it does not test or certify products. Assessment of conformity with ISO 12312-2 must be performed by qualified testing laboratories using appropriate equipment and methods.
Laboratory Accreditation
For test results to be credible, the testing laboratory must be accredited specifically for ISO 12312-2 testing by an organization that is a signatory to the International Laboratory Accreditation Cooperation (ILAC) Mutual Recognition Arrangement (MRA).
This means:
- The accreditation body conforms with ISO/IEC 17011
- The testing laboratory conforms with ISO/IEC 17025
- The laboratory has been specifically accredited for ISO 12312-2 testing
- The accreditation body has been peer-reviewed by ILAC
⚠️ "ISO Certified" Is Not a Thing
No product should claim to be "ISO certified," "ISO approved," or "ISO registered." ISO does not certify products. Any product bearing such claims demonstrates that the manufacturer has either not read or has chosen to ignore ISO's terms and conditions. This is a red flag.
What Valid Documentation Looks Like
Legitimate ISO 12312-2 compliance documentation includes:
- Test Report from an accredited laboratory showing test results for all requirements
- Accreditation Certificate showing the laboratory is accredited for ISO 12312-2 testing
- Scope of Accreditation confirming ISO 12312-2 is within the laboratory's accredited scope
For EU sales, additional documentation includes:
- EU Type Examination Certificate from a Notified Body
- Declaration of Conformity issued by the manufacturer
✓ What We Verify
- Test report covers ALL ISO 12312-2 requirements, not just transmittance
- Testing laboratory is accredited under ILAC MRA
- Laboratory's scope of accreditation includes ISO 12312-2
- Test report matches the actual products being sold
- For EU-ready products: valid Notified Body certification and DoC
The Complete Standard
ISO 12312-2 compliance requires meeting ALL requirements—not just the ones that are easy to test. We verify full compliance because that's what the standard requires, and that's what your eyes deserve.
- Transmittance within specified limits
- Uniformity across the filter surface
- Material free from defects
- Secure and safe mounting
- Complete and accurate labeling
- Testing by accredited laboratories