A critical analysis of CAPA certified headlights, by Daniel Stern:
https://www.thetruthaboutcars.com/2017/04/piston-slap-stern-talkin-oem-headlamps/
some excerpts:
Quote
...All of the aftermarket off-brand items (TYC, Depo, Anzo, DJAuto, Eagle Eye, Helix, Sonar, etc) are junk, whether they're OE-look alikes or restyled with clear lenses, projectors, halos, etc. The low price is attractive, but their quality, performance, and durability are all substantially and often dangerously inferior to the genuine lamps...
...There is little or no real optical engineering behind any of the aftermarket lamps — they are headlamp-shaped toys made from physical copies of the originals, which is not even close to adequate. One might as well try to cast new working contact lenses from a mould of your originals and expect to be able to see when you put 'em in your eyes. Even basic, low-tech headlamps are more akin to optical instruments than to the lamp on your bedside table...The level of shape accuracy required to accurately focus a headlight beam can only be achieved with precise optical engineering from scratch, using correct materials with tightly controlled manufacturing and quality control. All of those things are missing from the knockoffs, which don't even begin to get in the ballpark. Light distribution is not what it should be, and often the DOT certification marks are fraudulent...
...Perfect OE fit and performance" is often promised in the ads for the copycat lamps, and more recently they've been babbling about "CAPA certified" and "NSF certified" lamps, both of which are meaningless but sound impressive...
...The thing about "OE fit and performance" is a big belly-laff; take a look at this large test by the US Department of Transportation of original equipment vs. TYC and Depo versions of simple, American-vehicle headlamps: [censored] things don't even fit the car correctly, let alone come close to performing the way they're supposed to...
...So exactly what is being "certified" then? CAPA's criteria for lamp certification, called CAPA 301 QSM Section 12, concentrates heavily on the appearance of the lamp: it has to look substantially the same as the original lamp (minus trademarks belonging to the automaker, of course, because we're talking about unauthorized parts here). CAPA's criteria do not require that aftermarket lamps operate the same as the original lamp they're replacing in terms of performance, durability, weather resistance, vibration resistance, or anything else...What is this CAPA? It's the Certified Automotive Parts Association, an aftermarket-crash-parts lobbyist group that works hard to make sure your insurance company can stick you with inferior parts when they repair your car after a crash...
...Fine, so "CAPA certification" is a smokeshow, but doesn't saying the lights are "DOT/SAE approved" count for anything? No. It sounds official but also means nothing; there is no such thing as "DOT approval" or "SAE approval." ...The "DOT" marking on a headlamp does not mean the DOT or anyone else in any official capacity has scrutinized or tested the headlamp and judged it good. That's not how it works in North America. Instead, we have a system called "self-certification." The maker or importer of a vehicle or item of regulated vehicle equipment (such as a headlamp) proclaims an item meets all applicable standards. That's it. The "DOT" mark on the lens just means the maker or importer says, "I promise it's OK." '''
...on an older-model vehicle for which genuine lamps cannot be bought any more, one has no choice but to hold the nose and try to buy the least-worst aftermarket lamps. It's a crapshoot, and you're not going to get a lamp as good as the originals...But if you can get original lamps, that's definitely best; even for vehicles that have relatively low-performing original headlamps, the genuine lamp is almost always substantially better than the knockoff stuff...
