I'm surprised no one has mentioned the Vivitar Series 1 P/KA 105/2.5 (native 1:1) or the M42 90/2.5 +1:1 extender. These two are amazingly sharp and versatile lenses if you are willing to manual-focus, something that shouldn't be a real problem for macro work. The 90 is a storied lens - one that some people pursue for years.
Vivitar Series 1 90mm f/2.5 Macro in the Third Party Lens Review database.
I own the K-mount 105 - for a time here the interest in this lens drove the price up 100% in just a few weeks. It sucks in light but has such a thin depth of field that I am truly challenged to use it well. If I ever decide to actively pursue macro rather than just goofing around I will get a macro rail and use this right.
This is my
Vivitar Series 1 105/2.5 Macro pictured in the Third Party Lens Review database.
I also own the Tamron Adaptall-2 MF SP #52B 90/2.5 + the 1:1 extender and the 01F 2x TC. This lens is, if anything, sharper than the Vivitar and with the 01F 2:1 TC attached you can get equiv. 180mm working distance @ f/5.6. This lens has the most visible "snap" into focus I have ever seen on any lens and produces an interesting, if grainy bokeh.
Tamron Adaptall-2 SP #52B 90mm f/2.5 Tele-Macro in the Third Party Lens Review database.
I've had some success hand-holding this lens - and it is a servicebale portrait and short tele, to boot!!
Last edited by monochrome; 05-31-2009 at 05:29 PM.