I don't think there are any "best-kept secrets" any more, but there ARE some fine well-known bargains. Here are my suggestions and comments:
All the lenses you have seem to be Pentax bayonet (PK) mount. Many great bargain lenses have the M42 screwmount, which require an adapter. More on that below.
I'm not happy with any manual zooms that don't have an A setting on the aperture ring. Lack of the A means you may not get the best Shake Reduction. But that's my quirk.
CORRECTION: I misspoke. Shake Reduction is shaky with ALL manual zooms, not just non-A's.
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Many Ricoh and Sears (often Ricoh-made) PK primes are quite good. But BEWARE Ricoh-made lenses that are marked KR. These contain the infamous RICOH PIN. Mounted on your Pentax dSLR, they can be EXTREMELY difficult to remove.
Mamiya glass is also good, and Mamiya made some Sears lenses. Other names you'll see on good lenses (but not always with PK mounts) are Rikenon, Fujinon, and Yashinon. Some of these are still priced quite low.
You'll see the names Vivitar and Sigma on many lenses. Sigma is a maker; their products range from very good to not so good. Research any specific lens before you buy it. Vivitar is a marketer, with lenses from many makers. Viv glass has about the same quality curve as Sigma, with older lenses usually being better.
Older Vivitar Series 1 lenses are often astonishingly good, and astonishingly cheap. The most famous is the 70-210 zoom, especially (in order) Versions 3, 1, and 2. Avoid the later versions. (Google VIVITAR SERIES VERSION for details.) My Version 1 f/3.5 cost me a whole US$32 including shipping. It's about the only manual zoom I'm keeping. Newer (post-1985) Series 1 lenses are often crap.
There are still some Pentax / Asahi / Takumar bargain lenses out there, but they're going fast, what with Pentax/Hoya's recent spike in fame. Some are very good; a few aren't. See the lens database here for details. (Click on LENSES at the top of any Forum page.)
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Many of the best bargains, Pentax-made and otherwise, are M42 or M39 screwmounts. M39's can be difficult to identify, so I'll skip those for now. M42 was the standard before Pentax developed their bayonet PK mount. M42's are still being made after 70+ years. Some M42's can be difficult to use on a dSLR. And we have heated debates here about using various adapters. There's too much to go into now, so I'll just recommend getting an Official Pentax adapter, and using it with some of these great lenses:
First and foremost, the Helios-44 58/2 is incredible. Fast, sharp, and cheap. How cheap? BIN (buy-it-now) on eBay for around US$20. Other Russian glass labeled Helios, Jupiter, Mir, Industar, Tair, and Zenitar are also good deals. I got a NEW, huge, deadly sharp Jupiter-21M 200/4 for US$25. I got a tiny Industar-50 f/3.5 for US$13; put it on tubes and it's one of the best macro lenses around. Macro tubes are usually about US$8 per set, whether PK or M42; buy several sets.
The brands I mentioned above (Mamiya, Sears, Takumar, Vivitar etc) are on many superior M42 and PK lenses. Great bargains can be found under almost any of those names: 24/2.8, 28/2.8 (yours sounds decent), 35/2.8 or f/3.5, 50-55mm f/1.4-2 (you have one, but you can never have enough 50's), 100/2.8, 135/2.8 (yours should be OK), 200/4.
Other names to look for: Isco, Meyer, Enna (all German, all GOOD). Names that might be good, and might not: Lentar, Albinar, Suntar, and especially Hanimar / Hanimex and Porst and Spiratone. Those last few can be OK if they're REAL CHEAP. Some are best used for burning ants and throwing at stray dogs.
That's an overview. Keep asking questions.
Last edited by RioRico; 04-10-2010 at 06:19 PM.
Reason: correction
. I think using them for a while might give you some useful experience.
Originally posted by RioRico 
