Adding a telephoto lens

[TheWengler]

Hi All,
My set up includes the Pentax K100D, 16-45mm f/4 and 50mm f/1.4. This is my first SLR so I don't have much experience buying lenses. I've been looking to add a lens with a little more reach to my collection. A max focal length in or around 150-200 is what I'd like. I shoot a reasonable amount of macro so it'd be nice if the lens had that capability. I'm on a budget so I can only spend about $200-400. I know it's not likely to find a lens in this price range without some sort of issue but it's all I have to spend. Any suggestions or advice regarding this purchase would be greatly appreciated. Here are the lenses that I'm currently looking at:

Pentax 50-200mm - plenty of problems, no macro ($180 after rebate)
Tamron 24-135mm macro - too much overlap with current set up ($250 after rebate)
Tamron 90mm macro - no zoom ($380)
Sigma 70-300mm APO macro - rotating front element, poor border resolution ($200)
Sigma 105mm macro - no zoom ($350?)

[SpecialK]

Three of the lenses you list do not even meet your own requirements - 150-200 mm.

That leaves the 50-200 and 70-300. I have both, and the Pentax has a bit better IQ, is more compact, and is a little cheaper. You can add a close up filter if desired.

[TheWengler]

There is no hard requirement. I just listed the lenses that I was considering. How would you rate the AF speed/accuracy of the 70-300 compared to the 50-200? Thank you for the help.

[speaklightly]

The Wengler-

I recently found a Sigma 18-125mm lens on ebay for $140. Yes, I was holding my breath, worrying about lens condition and sharpness. However, all turned out well, the lens was in great shape and very sharp and quick to focus. I have seen others refer to lens as a "travel zoom," and I guess that would be a good use for that lens as it is quite small and easy to use.

Sarah Joyce

[SpecialK]

Can't tell much difference in AF speed between the Pentax and Sigma, though I would put them in the "slow" category (it may be the camera?).

If you increase the contrast (+3 in my case) the Sigma gets better at the long end, and with the "macro" mode (at 200-300mm) it might be your best choice. While I'm not so fond of mine, other people are very happy with it. Could have something to do with the reputed Sigma QC issues.