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Sigma 18-125mm 3.5-5.6

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	Mount: Pentax KAF2, APS-C sized CCD only! Build quality: ok to good Filter thread: 62mm Infrared Mark: no "Turn zoom", front element does not turn when zooming or focussing. I bought this lens because I wanted _one_ carry-around lens. I am aware of its limitations, both compared to less ambitious zooms and expecially primes. For some boring brick wall test images, look here.
Sigma 18-125mm @ 18mm (eq. 27mm) , f/3.5
		Sigma 18-125mm @ 18mm (27mm) You can see slight vignetting, but it's not too bad, considering this is "wide" open at f/3.5. Light fall-off across the frame is barely noticable in this real-life shot, but might become objectionable with different sky/foregrounds. We'll see.
Sigma 18-125mm @ 18mm, f/3.5 + Olympus WCON 08 (eq. 27mm*0.8=21.6mm)
		I had already bought an Olympus WCON 08B wide angle converter for my Dimage 7. It works nicely with it and it has a 62mm thread, just like the Sigma lens. So I tried the WCON on the Sigma. However, the vignetting is very strong. If you stop down the lens (this is at f/3.5), the vignetting becomes less (in area) but gets stronger (darker). You can crop it away to give a nice panoramic aspect-ratio, or, if it is just blue sky, clone it out. A WCON 08B isn't cheap and I doubt there are wide-angle converters that give better results with this lens. Currently, I regard this as a gimmick. Talking about distortion: Yes, it is there, but a) it's not terrible b) if you are distortion-conscious, the Sigma is the wrong lens for you in the first place c) it can be corrected in post-processing.
The "macro" mode of the Sigma is nothing to get too exited about. However, with enough light you can stop down and obtain a useful image. Shot with external TTL flash. Internal flash as fill flash. ISO 1600 here meant 1/1000 s exposure time. Not fast enough to stop action. ;) More shots with this lens in my Gallery: Sigma_18-125.html