What a UV400 Claim on Sunglasses Has to Prove
UV protection, polarisation and category numbers are the three claims that sell a pair of sunglasses. All three are measurable, which is exactly why they are the three worth holding evidence for.
- A public search of the BIS catalogue and the compulsory certification lists turns up no current Indian Standard specification for general-use sunglasses and no Quality Control Order. BIS approved on a sunglass listing usually means nothing.
- A filter category number measures visible darkness, not ultraviolet protection. ISO 12312-1 categories run 0 to 4 by luminous transmittance between 380 and 780 nm.
- ISO 12312-1 scores ultraviolet to 380 nm and notes that other standards use 400 nm, so UV400 is by construction a claim beyond the table and needs a spectral measurement to 400 nm on the finished filter.
- Category 4 filters are excluded from road use and driving by the standard, and category 0 filters cannot carry a useful polarising claim at all.
Three claims sell sunglasses in India: UV protection, polarisation, and a category number that implies darkness equals safety. All three are measurable, which is the problem, because a measurable claim is one a regulator, a marketplace or a competitor can check.
The general discipline of holding evidence before you publish is covered in the claim substantiation file. This piece is narrower: what these three claims assert, and what evidence sits behind each.
India has no sunglass standard, and that matters
Start with a negative, because it changes where the evidence comes from. A search of the Bureau of Indian Standards catalogue and of the published lists of products under compulsory certification turns up no current Indian Standard specification for general-use sunglasses, and no Quality Control Order covering them. The ophthalmic sectional committee, MHD 5, has standards on ophthalmic lenses, tinted ophthalmic glass, frame vocabulary, contact lenses and intraocular lenses, several from the 1970s. None is a sunglass specification.
The consequence is blunt. BIS approved on a sunglasses listing is almost always a claim with nothing behind it, in the way an ISI mark on a helmet is not. If a supplier offers a BIS certificate for a sunglass, ask which Indian Standard it is issued against. No domestic mandatory standard does not mean unregulated. It means the claims are judged as ordinary advertising claims, against whatever evidence you hold.
What a category number means, and what it does not
The standard the rest of the world tests to is ISO 12312-1:2022, Sunglasses and related eyewear, Part 1: Sunglasses for general use. Its scope covers all afocal, meaning plano power, sunglasses and clip-ons for general use including driving. It does not cover medically prescribed sun filters, nor products for direct observation of the sun, which sit in Part 2.
Table 1 assigns every sunglass filter to one of five categories by luminous transmittance measured over 380 to 780 nm at the lens reference point. Category 0 passes more than 80 per cent of visible light, category 1 over 43 and up to 80, category 2 over 18 and up to 43, category 3 over 8 and up to 18, and category 4 over 3 and up to 8 per cent.
A category number measures darkness in the visible band. It is not a UV measurement. Dark lenses with poor UV filtering are the classic hazard, because the pupil opens behind them.
UV400 is a claim about a band the standard stops short of
This is the detail that catches most brands out. Table 1 sets its ultraviolet requirements over two bands: solar UV-B from 280 to 315 nm, and solar UV-A from 315 to 380 nm. It carries an explicit note that some requirements in different standards stipulate 400 nm as the long wavelength limit of UV-A.
So UV400 is, by construction, a claim to perform beyond the band the standard’s own table scores. The standard anticipates that. Clause 5.3.5 deals with claimed transmittance properties, and clause 5.3.5.2 provides that where a product claims UV absorption or transmittance better than the Table 1 requirement, further requirements apply to that claim.
In plain terms, printing UV400 commits you to a spectral measurement out to 400 nm on the finished filter. A supplier saying the material is polycarbonate does not satisfy it. Polycarbonate does absorb strongly in the ultraviolet, which is why the claim is usually true. Usually true and evidenced are different states.
Polarised has a threshold, and category 0 cannot meet it
Polarisation is the claim most often made without any measurement, because the demo is a phone screen rather than a spectrometer. Clause 5.3.4.2 sets numbers. Where filters are claimed to be polarising, polarising efficiency shall be greater than 78 per cent for categories 2, 3 and 4, and greater than 60 per cent for category 1. The standard states flatly that category 0 filters do not have any useful polarising effect.
The same clause governs assembly, not just material. The planes of transmission must not deviate from the vertical by more than 5 degrees, and left to right misalignment must not exceed 6 degrees. A polarisation claim can therefore be true of the lens supplied and false of the sunglass assembled, which is the gap a factory lens certificate leaves open.
Driving is where a category error becomes a safety claim
Clause 5.3.2 is the one to read before a campaign shoot. Filters suitable for road use and driving shall be of categories 0, 1, 2 or 3, excluding category 4 entirely, and must pass two further tests: spectral transmittance between 475 and 650 nm of not less than 0.20 times the luminous transmittance, and a relative visual attenuation quotient for signal light detection of not less than 0.80 for red and 0.60 for yellow, green and blue. Clause 5.3.2.2 adds that filters below 75 per cent luminous transmittance are not for road use in twilight or at night.
A category 4 pair photographed behind a steering wheel is therefore making a claim the standard contradicts. So is a dark lens sold as a night driving aid. These are the eyewear claims with a plausible route to real harm, which changes how a complaint gets treated.
Tie the report to the thing you actually sell
Most eyewear claim failures here are not lies. They are evidence attached to the wrong object, and three traps account for most of them.
The report covers the lens blank rather than the finished mounted sunglass, so it says nothing about assembly tolerances or the mirror coating applied afterwards. Or it covers the base tint while gradient, mirrored and photochromic variants ship on the same certificate, although the standard treats them differently and doubles several tolerances for gradient and mirrored filters. Or the supplier changed and nobody re-tested, so the numbers have drifted past the allowed deviation of plus or minus 3 per cent absolute on declared luminous transmittance for categories 0 to 3, and plus or minus 30 per cent relative for category 4.
A usable file is narrow. Transmittance per ISO 18526-2:2020 clause 7, polarising efficiency per clause 15, a spectral curve rather than a pass stamp, model and colourway matching the listing, and a re-test trigger against any change of lens supplier, tint or coating. Modest annual cost against a claim printed on every unit, and the same logic is why front-of-pack claims deserve the same register.