Originally posted by Na Horuk I think the main problem are lenses like Samyang, Vivitar, Sears.. because they were made by various manufacturers. So they have some surprisingly good lenses, but some bad ones as well.
Sears IS Samyang, or at least the Sears Model 202's. The only outright bad lens I've come across from them is their 28-70 macro. The rest range from decent to outright amazing (for a department store lens).
When buying Sears (at least K-mount Sears) there appear to have been four manufacturers - Ricoh, Chinon, Tokina and Samyang.
Ricoh made most of the 50mm kit lenses, as well as most of the Sears KS bodies. The exception is (I think, not looking it up so this is off the top of my head) the Sears KSX-P, which was Chinon. Chinon also made a 50mm prime for Sears, which is identifiable because it has more aperture stops, a heftier build, and is slightly bulkier than the Ricoh 50's. The Chinons are more rare than the Ricohs by a good margin. They're also generally better lenses from what I've seen.
Everything not-a-50 seems to be either Samyang or Tokina. There could be another maker out there, but I'm really don't think there was.
The Samyangs are identifiable due to the fact that they're marked "Made in Korea" and are usually branded as a "Sears Model 202". Most range from decent to good. As I mentioned, the exception seems to be the 28-70 Macro. My copy is just awful, and every review I;ve seen of it mirrors the same issues - zero flare control, zero contrast, etc etc. You get Instagram without the work of using Instagram.
The best (at least in my opinion) are the older Sears K-mount lenses, which are generally black with silver piping and marked Made in Japan. These are the Tokinas and are basically the exact same lenses Tokina sold under its own name. They're heavy, mostly metal, and built like tanks. I have yet to hit a bad one, and (bearing in mind these are 1980's vintage lenses) are very good to excellent for the era they're coming from.
There are also some Sears lenses that *look* like a K-mount at a casual glance but very much are not - these are Mamaya/Sekors, and have a completely different mount. They seem to have been the bridge between the older M42's (I don't know much about the screwmounts, other than they seem to mostly be Ricoh/Tokina as well) and the K-mounts.
One last thing to note about the old Sears lenses - many of them have whats called the "Ricoh Pin" in them. Do yourself a favor and read up on that ASAP. You will want to either be very, very carefl with a lens that has that pin still intact, or do what many people do and grind it of or remove it entirely. It will jam on a modern Pentax DSLR and will induce much profanity and stress when you realize that you can't get your lens back off your camera after you've attached it. The thing to look for is they're usually marked as "KR". Of course that's 'usually'. It always pays to check when you're buying an old school third party lens, just in case.
Samyang also seems to have made a number of lenses for... just about everyone. If its marked as Korean, its *probably* a Samyang.
FWIW, I have the Tokina made 135mm, 300mm, 75-260 and... something else I'm missing as well as most (not quite all, but most) of the Sears 202's as well as most of the 50's (I'm missing the 50 1.4's, otherwise I have all of them).
Of course, the caveat to all of this is when you're buying 30+ year old lenses you really have no control over how people have treated them in the past. A lens thats otherwise stellar could be shot because someone ran it into the ground and you'd never know.