Discussion of lenses, brand or independent, uses and merits
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No, in short, as the new OS version has not yet arrived in the UK even at Sigma's HQ. For Alpha, I think the non-OS version is preferable. I like 1m close focus much better than 1.4m and a mere 1:8 subject scale. I tend to use these lenses for closer work than many people, and my subjects often come closer than 1.4m anyway.
David, I saw in your review of this lens that you also tested the 2X TC. How good is the AF speed with the TC? I believe when using the TC the A700/A900 won't be able to use the f/2.8 AF sensors, so it will focus slower, right? Is it very noticeable?
Focus has to be slowed down with the TC, or the camera can not operate. Same goes for the Sony TC, and every make. Because the TC effectively doubles the rate of focus change, the converter has to halve the speed of focus motor operation.
Also, the Sigma HSM while very fast is more 'jumpy' than, say, the 70-300mm SSM. It tends to find and lock single frame shots faster, but tracking can be a bit erratic with a tendency to overshoot and reverse in small increments during a pan following action at a changing distance.
I do not follow action much, I tend to shoot single fram and grab, so it works well for me.