Originally posted by watchingskyfallatm I had read somewhere on this forum that a great lens for macro stuff is the Pentax ashy, super Tacoma, f 1.8 50mm prime lens, but am not sure if that's something that has to be bought 2nd hand?
Probably referring to something like this:
SMC/S-M-C/Super-/Auto-/Takumar 55mm F1.8 Reviews - M42 Screwmount Normal Primes - Pentax Lens Reviews & Lens Database
Takumars are manual lenses, meaning you need to not only focus manually but set the aperture manually. They have many devoted fans, but a more modern lens with at least auto aperture will be a lot easier to use - without needing any of the complexities of extension rings, lens reversal and stop-down metering.
If your budget runs to $500 you have a wide choice of recent specialist macro lenses, including the ones mentioned above. I would endorse what others have said that something in the 90mm to 105mm range is best (eg Tamron 90 Pentax 100 or Sigma 105), because it allows more working distance from the subject.
I have the Pentax D FA 100 WR macro and it's just fabulous. Easily my best lens. The autofocus can hunt a lot, but that is a common feature of macro lenses. You often use them in manual focus mode anyway. But it's beautifully built and produces superb images. And WR means you can use it confidently in rain or snow. You would never regret buying one (available for about $500 second hand).